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THE COLLIERY ENGINEER CO 1896. 583575 1(. 5-. 54 Entered according to the Act of Congress in the Year 1895, By The Colliekv Engineer Co., In the Office of the Librarian of Congress, at Washington '" 1 PREFACE. \ I In preparing this little work the author has felt the difficulty which arises in a theoretical dissertation on scv eminently practical a subject as prospecting. It seems like giving rules and prescriptions for hunting or fishing or any other natural or practical pursuit. Though theory and practice are not at variance when happily combined, yet. either without the other proves very unsatisfactory. Tnus- the reader of this book, should he start out armed only with its theory, will find himself for some time pretty much " at sea " when he comes to actual practice in the field. As,. however, he gradually obtains some practical experience, he may find this little work of use to him. So, also, the seasoned prospector, who has hitherto trusted to luck, keen- ness of observation, intuition and experience, may find him- self in the future much better equipped by acquiring a little of the theory. Whilst we have endeavored to give the prospector all assistance in our power, as to {he best means of educating himself, describing his outfit, etc., we have devoted special attention to the description of such geological and other phe- nomena as he is likely to meet with in connection with his work, so that he may have an intelligent idea of them when he encounters them. We have selected just as much material as we think would be most interesting and useful to him, saving him the time and trouble of wading through heavy tomes and laboriously" picking out from a vast amount of, for his purpose, super- fluous matter, that which he will most require. The work is intended to be a popular one, addressed to the average student, prospector and miner and to the general public. The illustrations are largely drawn by the author from Colorado mines and Rocky Mountain subjects which are most familiar to him. ARTHUR LAKES, State School of Mines, Golden Citv, Colorado. January i, 1895. CONTENTS CHAPTER ^^'^^ I. On Prospecting— Preparation and Outfif for Work 7 II. The Prospector's Historical Geology 24 III. The Prospector's Paleontology or Study of Fossils 36 IV. The Prospector's Lithology or Study of Rocks.- 47 V. The Prospector's Mineralogy 59 VI. Ore Deposits— Theories Regarding the Origin of Ore Deposits 67 VII. Various Forms of Ore Deposits 83 VIII. Relation of Veins to Eruptive Forces 93 IX. Gold Placers -- 104 X. Deep Leads.. m XI. Mining Regions— Showing Examples of Ore Deposits.. 117 XII. Ore Deposits in Sedimentary Rocks 151 XIII. Examining and Sampling Mining Properties, Prospects or Mines ^74 XIV. SaltingMines 1S5 XV. Prospectors' Tools, and How to Sharpen and Temper Them -. - --- 192 XVI. Some Elements of Mining Law Relating to Prospecting. 200 iJlM chaptp:r I. ON PROSPECTING— PREPARATION AND OUTFIT FOR WORK. The regular prcjsnector, as a rule, has at some time of his checquererl career had some actual experience in the mines themselves, from which he has learned by observation, the appearance of different ores, their different values, how the veins appear on the surface, h(JW to open a vein, and the uses of pick, shcn'cl, and blasting powder. In a word he is a miner, who has become too restless to stick to steady work, and so follows the more uncertain and precarious livelihood of seeking for new and undiscovered veins, many of which even in an old mining district may yet be dis- covered covered up by brush or debris, whilst a new district offers a most enticing field. These mineral veins or ledges, may make him in a moment a comparatively rich man, and if he finds them, they will cost him nothing, only a simple com- f)liance with the inexpensive regulations of the law. So the ife of a prospector offers many attractions to one who is restless and loves to roam and loves to find something new and is not afraid of considerable hardship. To save a vast amount of time and labor, he should acquire knowledge. Thus, for instance, if he were prospecting for coal he would be wasting his time in hunting for it in granite, or if he was hunting for the precious metals, he would lose time in looking for them among the unaltered sedimentary strata of the prairie. This is merely for example, but an infinite variety of knowledge is necessary for him in his vocation, besides even that of the simpler elements of geology, such as the knowledge of different kinds of minerals, and their value, the kind of places and peculiar rocks they are associated with, their appearance on the surface, etc., etc. 8 to^'cther with some knowledge of assaying or blowpiping or panning. In a newly rlisccjvered camp, men will rush in lor a lew weeks, work' a little in the dinerent mines, suflkient to give them an idea of the kind of ores and rocks and other circumstances in the locality, and then will strike out on their own account and prospect around the camp for new veins or extensions of those already discovered. An extension, by th.e way, of a very rich discovered lode is nl»l«\^*A x^ifciic can be seen by the traveler from the windows as he glides throueh in the railway car, and the inquiring prospector or geologist can examine and study this vast section leisurely on his mule or on foot, without doing any climbing and on a good road. Smaller partial sections can be similarly studied along many of the streams issuing from the Kocky Mountains among the foothills of Colorado, buch, tor 19 flanks of the niouiitain and "fi^cncralized inoutitains and fcjothills on prairie. Both of these are or "made up' of actual the border of ideal sections partial typical sections found in dilTerent localities in Colorado, the vertical Grani/-e 4 Gfte/Si tviHf Porphyry Gold. j//yer Lead, I tort ARCH/tAN V \ Do/o.mife ' * fiorpkyrv ('onglomerate TRIASSIC I' # Iron t A/lounta/zi ^ and Path Region I ^ ^ ^ Footh'ilh Pr,ATE II. Generalized Section of Rocky Mountains in Colorado, Showing Economii can be seen b)' the traveler from the windows as he glides through in the railway car, and the inquiring prospector or geologist can examine and study this vast section leisurely on his mule or on foot, without doing any climbing and on a good road. Smaller partial sections can be similarly studied along many of the streams issuing from the Rocky Mountains among the foothills of Colorado. Such, for /.aya MaP/affM /^ £kr A i: E 'a ir $ L6v^erjjp%f ll'viSAfV Colly/do ''(iroup^^r:"''^rLat^^M^:^^xitoup TERTIARY At/ej/ci.1 Baiiftss: /'.^f/oty ^ooft f >4 I btoup Footti'ilh and Hogbdclf^ ' V Plate II. s in Colorado, StiowiiiR Economical Products in Different V Table Land3 V" --/v. Plains >• — \ 9 t8 will probably be ditfcrent to what tbey wore in the loothills. Heat has so'chan>,a'fi or metaiiiorphosed tlie sandstones and shales, that they are scarcely rei-ojrnizai)le as the same rocks •« f ■» ' .*I.MI« Vr,* niFon Vtorp -I liiirlilv SMIClllcd I I I In illustration of what we have said, let us take the two engraved generalized sections showing all we know of the crust of the earth as exposed in Colorado. JMates I and II. Plate I is a vertical section of an ideal cliff, showing all the members of the various periods in a stupendous cliff resting on fundamental Archx*an granite at the bottom of a canyon. Plate II represents the same rocks and succession of strata displayed in upturned "hog backs" along the 19 Hanks ot the mountains and foothills f)ij the borrlcr of mountain aiul prairio. Roth of these are ideal sections " j^enerali/efi " or "made up" of actual partial typical sections found in dilTerent localities in Colorado, the vertical one in detachefl and sometimes wiflely separated districts in the heart of the nujuntains; the other at similarly distinct and different localities alonjj^ the l)anks of the various rivers issuinjj^ from these canycjns in the mountains, cuttinj^ their way throujj[h the upturned strata of the llankinjj; foothills and debouchinj^ on the prairie. It is very rare to find at one locility anywhere in the world, a complete section of the earth's crust exposed. The nearest approach io this in Colorado, is the remarkatile section between Coh^rado Springs and Manitou, which shows alonj^ the waj^on road the successi(jn of strata from Arcluian to (Juaternary. One of the most remarkable vertical sections in the W(jrld, is in the grand canyon (jf the Colorado Ri\er, where the stupendous clifTs show in one face, a thickness of some 6,000 to 7,000 feet of strata, representing several geological Ceriods, but by no means a complete section of all that is ncnvn of the earth's crust. To show how ditFicuit and rare it is to to get a complete secticjii of ^;// the periods in the earth's crust, we may state that sometimes the rocks of a single geological period are from 10,000 to 20,000 feet thick. A canyon might thus be cut to a depth of 5.000 feet, and yet be in only part of a single earth-period. By lar the most extensive and available sections are, like those represented in the engraving, along the courses of streams on the Hanks of a mountain range. It would be a formidable task to scale a cliff 5,000 feet high and examine minutely, in ascending, each of its geological divisions; whilst, on the other hand in the foothill regions, a pros- pector may walk over and mark and study as nmch as 10,000 to 40,000 feet of strata along the banks of a river in a single aftcnoon. In the Weber Canyon in Utah, as much as 40,000 feet of strata, composing the flanks of the Wahsatch Range, can be seen by the traveler from the windows as he glides through in the railway car, and the inquiring prospector or geologist can examine and study this \'ast section leisurely on his mule or on foot, without doing any climbing and on a good road. Smaller partial sections can be similarly studied along many of the streams issuing from the Rocky Mountains among the foothills of Colorado. Such, for 20 I II example, as at Boulder Creek, Clear Creek, Bear Creek, the Platte River, and, most complete of all, the one along Fountain Creek, near Colorado Spiings, which we have already mentioned. Similar sections can be found in most mountain regions, such as the Adirondacks in the East, and the Sierra Nevada and Coast Range in the West of America. We emphasize again, that the close study of these is the best preliminary step we know of in a j^ rospector's geological education. Let us now examine our ideal generalized Colorado section which we will suppose to be all exposed along the banks or canyon of a single river. We will start from the Archaean granite in the canyon, thus giving us a sure and known and lowest possible geological horizon to begin with. THE ARCH.1i AN. This Archaean we find to be composed towards its core, of solid, shapeless (amorphous) crystalline granite, which seems to have been fused out of all shape by water and lire, or aqueo-igneous fusion. With this, but more characteristic of the upper and outer edge of the Archaean, the granite assumes a more stratified and bedded character, which we designate as "gneiss " and interbedded with it at intervals are distinctly laminated or finely leafed strata, called schist; all these varieties are composed of the same minerals in different arrangement and quantity, viz., mica, quartz, horn- blende, and feldspar. As these rocks are semi-igneous or metamorphic, we find no fossils in them. Traversing all these Archa;an rocks and cutting them at all sorts of angles, we may notice some eruptive dykes of porphj-rv, which were once certainly molten and have ascer.ded in that state through fissures opened in the rocks from depths and sources unknown. As we approach the edge of the granite we may even see some of these molten rocks, insinuating once fiery tongues among the weak places and bedding planes of the overlying sedimentary strata, as represented in the diagram, where one dyke is shown to have sent out so thick an intrusive sheet of porphyry, (see Plate II), between the overlying limestones, that where subsequent erosion took place, this thick sheet, by its superior hardness, was left to form the highest cap of the mountain, as on many of our prominent mountain peaks such as Mt. Lincoln and others in South Park. Besides these rocks, the prospector will observe numbers of quartz and pink feldspar veins of all sizes, some mere 21 streaks and occupying incipient fissures or weak places (veins of segregation), others occupying large well defined fissures or jointing planes (so called true fissure veins). Some of these may or may not carry metal, gold or silver, lead or copper, at any rate he will pay them especial atten- tion particularly if any of them look' at all decomposed or rusty, or are in close proximity to an eruptive porphyry dyke. THE CAMBRIAN. Now the prospector emerges from the Archiean granite and finds the first true sedimentary, water-formed rocks lying where the ancient seas placed them, on the eroded upturned edges of the granitic series. If this section should be near the plains or foothills, this first sedimentary rock will be a sandstone, pure and simple, or a conglomerate of little pebbles, but in the parks and center of the mountains where these ancient strata are most conspicuous, the first rock lying on the granite is a hard, white, semi-crystalline quartzite or metamorphosed sandstone. He may possibly find some obscure signs of ancient fossil shells in this series, which is called the Cam- brian now, though formerly it was held to be only a lowei division of the Silurian. In Colorado these Cambrian rocks rarely exceed 200 or 300 feet in thickness, but in other regions they are often very much thicker. In this series the prospector may look for precious ore, more especially gold. He will carefully look also for intrusions of eruptive porphyry in this series, as at the junction of this with the quartzite, ore is most likely to be found. He will also observe any rusty signs filling cracks, as good indications of gold bearing ore. Silver also may be found associated with lead or zinc. SILURIAN. Walking along, he next comes to some 200 or 300 feet of drab-yellowish or light gray thin bedded limestone of a dolomitic character, characterized by numbers of little white flints or (rarely in Colorado) by some fossil shells, which, by reference to the engravings in his manual, he finds to be Silurian, and so recognizes the series. Here he may find indications of lead, silver or other ores, but not much gold as a rule. CARBONIFEROU.S. The next series of this should, according to the text- books, be the Devonian, characterized by fossil fishes and 22 I *'()ld Red" sandstones; but tht rocks of this epoch for some reason are missing in C )iorado. Instead of this, rest- ing on the Silurian, he finds a thick bed of heavy bedded, massive, " blue-grey " limestone, characterized by black flints, and at rare intervals by fossil shells and corals, which again, by reference to his book, he finds to be characteristic of the Lower Carboniferous. This limestone when traversed by sheets of eruptive porphyry, has yielded at Leadville and at Aspen and New ^Iexico and Arizona, some of the largest si'/er-lead dep<;sits in the West. In fact, throughout the West it may be considered as the main silver-lead horizon. This limestone is generally betv/een 200 and 300 feet in thickness and readily recognized by its position relativ'e to the Silurian below it. and the massiveness of the strata, and their dark grey color. It is commonly called the " Blue Limestone " in Colorado. I ^ MIDDLE CARBONIFEROUS. Next on this, is a bed of dark black shales in which thin seams are sometimes found, and fossil plants, like those in the coal strata of Peunsylvania, sufficient to show that it. too, belongs to the Carboniferous. This is followed by some 2,000 or more feet of "grits," rough, hard, gritty sandstones, partially changing into quartzite, akin to the •• mill-stone grits" of the Eastern States. A few limestones occur in this thick Middle Carboniferous series, which locally, when capped by porphyry, produce silver-lead deposits ; but generally speaking, the "grits " are unproduc- tive in Colorado. The Upper Carboniferous consists of beds of gypsiferous shale and heavy, brownish red conglomerate sandstones. TRIASSIC "RED-BEDS," From these we pass into a series of heavy bedded, coarse conglomerate sandstones of a brick-red color, commonly known as the " Red Bed? " in Colorado ; little indications of ore are to be expected in this series. The prevailing redness of the series makes it an easUy recognized geological horizon in Colorado and elsewhere. The thickness in Colorado varies from 1,000 to 2,000 feet. JURASSIC. Next, the prospector comes to a softer and more varie- gated series, consisting largely of pink, green, red, or 23 maroon marls and clays, with some thin limestones and red sandstones. This is the Jurassic series in which some remarkable lizard remains, called Dinosaurs, have been found, proving the correctness of its Jurassic name. This is not a likely mineral horizon, generally speaking, in Colorado. CRETACF.OUS. These softer beds are capped by a hard massive sandstone about 200 feet thick, forming by reason of its superi(jr hardness a prominent hog back in the prairie or foothill region. Fossil remains of leaves show it to be a land and fresh-water group, which is called the Dak ' di group. This group in Colorado forms the base of the great Cretaceous system ; lying on it, is an enormous thickness (jf drab shales with a few limestones characterized by fossil sea shells, showing the group to be the marine Cretaceous, likewise a poor prospecting ground. Towards the upper portion, these shales pass gradually into heavy bedded sandstones containing several seams of coal, and many impressions of tropical foliage. This is the Laramie group of the Cretaceous, evidentl}'^ of fresh water origin, and noted as the main coal producing horizon in Colorado and the West. TERTIARY. On this, at a somewhat gentler angle even to horizontality, rest thick beds of shale and claj'^ and conglomerate, com- posed of volcanic detritus and pebbles, showing that at the time these Tertiary beds were being laid down by large fresh water lakes and marshes surrounded by tropical foliage, volcanic eruptions on a grand scale repeatedly occurred. Hence it is that many of the Tertiary beds are preserved from erosion by being capped with v^jlcanic rocks, such as basalt, andesite, or rhyolite, as at the Table Mountains at Golden, on the Divide near Colorado Springs, and elsewhere in Colorado. One of these lava capped "mesas" is represented in the section, Plate II. Fossil leaves and coal seams are found in this period. QUATERNARY. Lastly, strewn indiscriminately over all the formations is the " Ouaternary drift " composed of loose pebbles, and sands, and clays, the material derived from rocks of all the periods through the agency of glaciers and streams. Here the prospector will pan for his ^old placer, and in his search may possibly come across the teeth or tusks of the great Mammoth or fossil elephant, together with the first indications of the presence of primitive man. The pebbles by their variety will form a fertile subject of study to determine to what class of rocks they belong. This ends the prospector's first preliminary lesson in Colorado; but taking this section as a type, he may to his great advantage, similarly study other sections far remote from Colorado. In Colorado, if he knows this section by heart, he has the key to nearly all our mountain structure, and will be at home wherever he goes. He will be struck, too, to see to how small a portion of this great section the precious metals are more or less confined, principally to the Archai^an and Paleozoic rocks. CHAPTER II. 'I THE PROSPECTOR'S HISTORICAL GEOLOGY. In our last chapter ,ve gave some hints to the prospector how to commence his geological studies, and gave him an example of a geological section o<" the foothills and moun- tains of Colorado, and how to otudy it in detail practically. Having completed this study, if a thoughtful man, he will like to know more of the natural history of all this section of the earth's crust : what is the natural history of the Archa,'an, the Cambrian, Silurian, etc., why do some of these strata contain sea shells, ?.nd others land plants, why are some evidently of marine, and others of fresh water origin, and particularly why are some especially metalliferous, and others not so much so. We propose, therefore, in this chapter to give him a brief sketch of the earth's history as exemplified in the section, Plates I. and II. HYPOTHETICAL ORIGIN OB' THE EARTH. The world was not " spoken into existence ready made " in the state we now find it. It has attained this condition through a multitude of gra -al changes and revolutions which have taken millions ' rears to accomplish. The I 25 'i remote history of the earth's origin is a matter of hypothesis and speculation. There arc reasons for supposing that at (jne time its elements were in a gaseous condition, and that this planet was an incandescent luminous cloud revolving through space, gradually consolidating into a molten ball surrounded still by an atmosphere of gases, a condition perhaps not very unlike that of the sun, whose interior by some is supposed to be passing into the molten state, while its exterior consists of various incandescent gases arranged more or less according to their specific gravities. The spectroscope has detected the elements of some of our earth metals and minerals in the sun in > tate of vapor. The ultimate source of the precious mei...s is again a matter of speculation like the nebular hypothesis we have alluded to, by which the earth, as we have said, is supposed to have arrived at its present condition as the result from the gradual cooling of an incandescent mass, and as the specific gravity of the crust is much lesf. than that of the whole mass of the earth, it has been i.iferied that the heavy metals must be in much larger proportion in the interior of the earth, than in the rocky crust, though this greater interior specific gravity might be also accounted for by the rocks of trie interior being much more tightly packed by enormous pressure than those near the surface. Volcanic emanations and hot springs contain metallic minerals, so also do the waters of the ocean. But we know not from what depth the former came, nor from what source the latter dcved them. As circulating waters take up and throw down their metallic contents under varying conditions, the same material may have been deposited more than once, and in more than one form since it reached the rocky crust. l^pon the cooling of the ball, a crust formed like that on molten iron, crumpled and corrugated by contraction, due to cooling, into an uneven surface, with comparatively slight elevations and depressions, and doubtless broken through here and there by great fissures and volcanic craters, through which the molten flood beneath poured out in volumes, adding to the thickness of the congealing crust. Upon such a surface the gaseous atmosphere, gradually cooling and condensing, descended as hot chemical rain,, and filled the troughs of the crumpled surface with a hot, chemical, steamy ocean. Whatever land of primitive lava rose above this ocean was battered by the waves, reduced to sediment, and deposited as the first'sedimentary strata in the bed of that prima3val ocean, the eruptions from below !■ . I h i r ! 26 the thin crust doubtless contributing largely to the same material. ARCH.EAN AGE. Thus, perhaps, were formed the first stratified rocks of the world, which we have an opportunity of actually seeing and studying, viz.: the granitic series, with its varieties of gneiss, schist, syenite, etc., and as this is the beginning age so far as we know, we call it the Archaean, the Greek for begin- ning. It would seem probable, however, that these granitic rocks forming the axes of our mountains, may not, at least in part, have been the very first rocks of the crust, for we observe some of them such as the gneisses and schists to be stratified, and to show elements in them seemingly derived from other and still older rocks, which latter may or may not have belonged to the original cooling crust. Some geologists claim that the Archajan is the first cooled crust and attribute it to a molten origin. This may be true for the seemingly fused massive amorphous granites (though these may be but the result of aqueo-igneous fusion of sediment or extreme metamorphic action), but scared}' for the stratified gneisses and schists, though it is to be noted that a sort of stratified or schistose structure is sometimes observed in truly igneous rocks and may be induced by peculiar arrangement of minerals, pressure and cleavage, instead of water lamination. The subject is a difficult one and too abstruse for the limits of this work. In the scale of geological periods in the text-books, we sometim es find this great Archaean divided into two or more groups such as the Laurentian, Huronian and of late the Algonkian. The Laurentian is the oldest and may be called the Archaean proper, wliilst Huronian and Algonkian may be grouped generally as Pre-Cambrian, or series of rocks laid down after the Laurentian and before the Cam- brian. All the rocks are of a highly crystalline order and bave a peculiar and distinct general appearance different, as a rule, to those of any subsequent geological periods and so not easily mistaken for them, consisting in the lower division, mainly of granite, gneiss and schists, and in the upper divisions of gneisses, schists, quartzites, slates, some marble, serpentine, etc. The upper or Pre-Cambrian series is not nearly so universally found as the Laurentian or Archaean proper. In Colorado we find the Pre-Cambrian represented locally in South Boulder and Coal Creek canyons, along n the foothills, also near Salida in the Arkansas valley, in the Ouartzite range and on the road between Ironton and Ouray in the San Juan Mountains. The new Kootanie silver mining district of British Columbia, seems to be largely in these Pre-Cambrian rocks. This Pre-Cambrian is usually very thick, numbering many thousands of feet. It is distinct from the Archaian prober or Laurentian by lying on tht latter at a different angle, in other words •unconformable." The rocks, too, do not contain so much of the heavy massive granites, and heavy bedded gneisses as the Laurentian, but are more characterized by quartzites, by conglomeratic gneisses and schists, and show clearly that though highly metamorphosed and crystalline,]? they Plate III. Archaean Rocks. are of true fragmental and aqueous origin, for the pebbles in the gneiss are often very distinct, and ripple marks are not uncommon on the quartzites and slates and schists. The material was doubtless derived by waters from that of the underlying and older Laurentian. The whole Archaean series, however, has evidently passed through an ordeal of heat, such as is called aqueo-igneous heat, and all its ele- ments are in a highly crystalline condition. Its strata are intensely folded and crumpled. See Plate III. Signs of life, in the upper series even, are exceedingly obscure and doubtful, such as graphite and possibly corals. Great iron beds also occur, indirect proofs perhaps of the previous existence of life. 28 I I •' i li We have been thus particular with this Archxan Age because its rocks are of great importance to the prospector, being the main repositories of gold, silver and the precious metals thoughout the world. Moreover many of the other and newer rocks containing gold and silver have been made from the detritus of this, and the gold placer beds largely from the detrituo of the rocks and porphyries found in this age. Thus the Archaean may be considered as the parent of nearly all the other rocks. When later we have studied the origin of ore deposits, we shall see how eminently the Archxan Age with its attendant heat, chemical reactions, Assuring, metamorphism and volcanic eruptions was favor- able to the diffusion and concentration of precious ores in its rocks. CAMBRIAN AND SILURIAN AGES. Cooling and consequent contractions still progressing in the globe, fresh and greater wrinkles and corrugations were caused on the surface of its crust, and some of these granite seabottom strata were crumpled up, till the crumples arose above the then universal ocean as low islands or reefs. The ocean had by this time cooled sufficiently to support low forms of marine life, and so along the flanks of these granitic islands, coraJs formed reefs, shell fish swarmed and sea weeds grew. Sands formed by the waves from the material of the granite were laid down as shore-line beaches, often mixed with shells ; and in deeper water, corals were forming limestones as at the E resent day, both, by time and pressure, consolidating into ard rock, eventually it may be, metamorphosed by heat into a semi-crystalline hardness, as in the case of the Cambrian quartzite and Silurian limestones, the latter some- times changed to marble. If these Cambrian quartzites were formed from the detritus of the granite and the granitic series is the source of gold, it is not surprising that we find the Cambrian quartzites locally rich in gold, as they were the auriferous sea beaches (like those of to-daj^ in California which are gold bearing) of that period, later consolidated into hard rock. In Colorado the Cambrian quartzites are only locally prolific in gold, as at Red Cliff, but as they have hitherto been much overlooked by pros- pectors they are worthy of closer attention by the gol.l seekers. The limestone not being of a true fragmental origin but formed by the slow work of corals, could not be expected on consolidation to be a recipient of gold, but 39 later by its peculiar chemical C(jinposition, of which we will speak hereafter, and by its cavernous nature, it furnished a more convenient receptacle for silver and lead ores. So then in Colorado and in other regions, we find first the upheaved crumpled granite of the old Archaean island, and on these the Cambrian sandstone or quart/ite beach of "golden sands" with some fossil shells, and upon this again Silurian limestone with relics of fossil corals and shells. So we call these ages the Cambrian and Silurian because the fossil shells and corals are peculiar to those ages and distinct from those of later periods or the present day. Plate IV. America at Close of Archaean. North America at the beginning of these periods was barely outlined by a few granite islands congregating mainly in the region now occupied by Canada, wnilst one or two reefs or scattered chains of islands marked the site of the Eastern ranges of mountains, and a few parallel granite islands outlined the site of the principal uplifts or future great ranges of the Western Cordilleras. All else was ocean, and that ocean was depositing its Cambrian beaches and Silurian coral limestones against or near these granite islands destined in time to grow into lofty mountain ranges. 30 and to bcconif the Ijackbone of the American Continent. See Plate IV. DEVONIAN. The Devonian which should come next in order in the geological tree appears to be absent in Colorado but is well shown at the Eureka Mines in Nevada. The rocks appear to be mostly r.arine limestone full of corals and shells and a few remains < f gigantic fishes for which this age was celebrated. Land plants and some coal are found in it in the East. Lead silver ores may be expected in the lime- stones of this age, and in Cornwall (England) Devonian slates traversed by quartz porphyries are the main rocks carrying tin ore, a metal very scarce at present in North America. pi^';XS"^'^<7/^. S^-^/^. Cenozoic Plate V. Section showing Unconformity of Geological Eras. These ages we are speaking of are separated or distin- guishable from one another by decided and characteristic changes in the fossil, animal and vegetable life existing between one age and another, also in some countries by marked unconformability of the rocks, /. c, the rocks of one age lying at a different angle upor the upturned rocks of a previous age marking great oscillations between sea and land. In America, however, these oscillations between sea and land seem to have been less than in Europe, and we find a general uniform rise of the continent from the primitive oceans, and an orderly succession of strata lying against the flanks of the ever rising granite nucleus of both mountains and continent. Hence to distinguish the dilTerent ages we are driven more to the study of fossils and lithological peculiarities than deriving anv help from observed marked uncontormabilitv. See Plate V, in which the strata of the 3» flilTcrcnt cms lie upon one another cit different anjjfh's. and tiie glacial and (juaternary drift pebbles and clays are strewn unconlorniably also ovxm' the tops of ihc uptilted and er(jdud strata of all the eras beneath. CAkHONlKKKOUS. In the Kastern States as the American continent jj^radnally rose from the sea, and to the granite islands had been added a Cambrian, Silurian, and Devonian shore, with further unefpial elevation, a kind of wide trouf^h or synclinal fold or riepression appears to ha\'e been formed between the middle and eastern part of America, which was at first occupied by a wide arm of the sea, later, by continued elevation, by a great body of fresh water, and later by low marshes and low marshy islands barely above sea-level. Up(jn these low lying lands grew a dense vegetation unlike any of the pr sent day, but resembling somewhat the tree ferns of our southern semi-tropical States. This low lying region was subject to freshets and inundations from the surrounding higher regions, periodically deluging the swamps and swamp vegetation with liver and flood deposits of pebbles and sand, under pressure (jf which the peat gradually turned into coal. Successive coal seams were formed by successive growths of vegetation bi ween the intervals of periodic inundation, or of subsidence and possibly at times of upheavals, for these low lands, as sediments accumulated, appear at times to have sunk below the sea and again to ha\'e been either built up abo\'e it by fresh supplies of sediment, or to have been temporarily raised up by upheaving forces. Finally by a grand revolution which closed the Carbonif- erous age in America, the coal swamps with their coidbeds and strata were crumpled up to form the present great Appalachian Chain. Similar movements no doubt took place about the same time in the Rocky Mountain and Western region. But here the marine condition seerns to have predominated over the fresh water one, for we find the Carboniferous in Colorado more represented by marine fossiliferous lime- stones and sandstones than by those of fresh water origin, though the Weber-grits may have had a fresh water origin, as in a few rare instances we find fossil plants like those in Pennsylvania together with a few insignificant small seams of coal. But in the West it is evident that the circum- I' 4 stances from one cause or another were not favorable for the production and f,^rowth of extensive coal-beds as in the Eastern States. The coal forniinjif time was reserved in the West for a much later period, vi/.: the Laramie or l'p|)er Cretaceous. The Lower Carboniferous in Colorado, how- ever, contains in its limestones much of our silver-lead wealth as at Leadville and Asjien. The Cambrian, Silurian. l)evonian, and Carboniferous Af,^es have been grouped toj.jether by j^-eoloj^ists into one great era, the Paleozoic, owing to a general family likeness in the fossil fauna and flora of these ages. To the Arcluean and Paleo/oir rocks the bulk of our veins and deposits of gold and siher are mainly confined, thouc^h both in Colorado and elsewhere, as will appear later if certain peculiar conditions are present, the rocks of the later and newer periods may also in some regions produce precious ores. Hut the prospector should gi\'e his closest attention to these older rocks, hence we have de\'oted extra space to their (iescription anrl history. TRIASSIC AND JURASSIC, OR JURA-TRIAS. Aft^r the Carboniferous, followed the Triassic and Ju- rassic; sometimes in America, owing to the didiculty of positively separating the two periods, they are combined under one name, the Jura-Trias, and in Colorado are locally called the " Red-Beds," owing to their prevailing red and variegated colors. The series is well represented in the celebrated Garden of the (lods, near Colorado Springs. The red conglomerate sandstone of the Trias proper, has so far yielded no determinative fossds, but the variegated clays in the upper Jurassic at Morrison and elsewhere have yielded some remarkable Saurian remains of land lizards. It is probable from the presence of salt and gypsum in these red-beds, and the prex'ailing redness of the rocks, due to iron, which was not leached out through the agency of organic life, and the general absence of fossil remains, that the lower portion of these rocks was laid down in land- locked salt seas, or salt lakes, shunned by both vegetable and animal life. The upper portions, however, show evi- dence of the existence of land of a low marshy character, with fresh water and probably large estuaries, as we find the remains of turtles, crocodiles, fresh water shelh. and Dino- saurs or land lizards. The rocks of these periods are not generally prolific in ores. The Silver Reef sandstone of 33 rtah is :in exception, which contains chloride of silver (lisseniinated throuifh it. When piercerl hy eriipti\e rocks, however, ore should be looked for in this series as else- where. CRKTACF.OUS I'KRIOD. V this followed the Cretaceous, a series of very I'pon thick formations, numbering several thousands of feet in Colorado, consistinf^ in its middle portion of limestones, and thick beds of drab shale. These are mostly marine, as shown by the sea shells in them, but at the base is what is called the Dakotah group or Cretaceous No. i, a prominent Platf. VI. North America in the Cretaceous. sandstone hogback in which the fossil impressions of leaves, very like, but not identical with those of the jiresent day,, show that land and fresh water existed at the time. The- limestones and clays of the middle or Colorado group,, contain cjuantities of fossil marine shells, such as the Nautilus, Ammonite, Baculite and Inoceramus. The Laramie forms the upper group of the Cretaceous, and contains our principal western coal fields and abounds- in fossil remains of tropical foliage. This Laramie group marks an important era in our Rocky Mountain region for it shows that beginning of the great Rocky Mountain revolution, by which the granite islands 1' ^ "rm a BOrttfcSa S ^ iiaiatB 34 before mentioned, against which all the previous sediments had been forming mainly beneath the sea, were elevated lo.ooo feet or more into continental or mountainous masses, dragging up with them portions of the sea bottom and ex- posing it as land surface, dr i.uing otT the shallow Creta- ceous sea which had hitherto divided the Eastern half of the American continent from the Western, bringing on a land and continental condition, which was com))leted in the fol- lowing Tertiarv age and has continued to the present. See plate VI. The Jurassic, Triassic and Cretaceous are grouped into one main division called the Mesozoic or middle life era of the world's history. None of the rocks of this age in Col- orado are celebrated for ore deposits, e.xccpt locally under local conditions. In California and portions of the extreme West where these rocks have been highly metamorphosed by heat and penetrated by igneous rocks, some of the leading ore de- posits of gold and silver are found. The same remark applies also to the succeeding Tertiary in those regions, particularly in the Sierra Ne\ada and Coast ranges. i ^ !\ ■ ./.: TERTIARY. The Tertiary age seems in the Rocky Mountains to mark an era of comparative rest in mountain elevation, for the strata forming some of the divisions of this age lie ahuost horizontally upon the tops of the earlier upturned periods. These beds were formed by fresh water lakes 'm Colorado surrounded by tropical \'egetation. In the Coast ranges of California the Tertiary is upturned into mountain forms and metamorphosed, and, from the presence of sea shells, is clearly of marine origin. The Tertiary in Colorado is best seen in outlying table lands. In Wyoming the Tertiary lake formed the Careen River beds and Bad Lands abounding in fossil mammals, leaves, fishes and insects. The Tertiar\' was the world's tropical summer, a period of beautiful lakes of semi tropical foliage and a warm climate. In certain regions it was disturbed by gigantic revolutions which up- heaved the Himalayas and the Alps. Such revolutions as occurred in our Western Cordillera svstem were marked by enoruKJUs ebullitions of lawis of various kinds issuing frminQ Thin Lignite codl Metamorphosed Sdndstcnt . Gold bearing m California also flshphalt in Colorado andCalifotnia Gypsum Oil and Lime & Md Building 3rone ^ Copper j/l/ca forG/as5 Silver. Reef Sanablone 5omeffailB/Jilcling Stone Eastern Coat of Pennsylvania Silver. Lead futeka. Nevada Silver Lead Deposits t^arbte Jitver. Lead Iron Gold Gold. Olivet LeadZittcCopper^c. Iron i^an. But halo Be. Elepiiantsteetii^Bones Man Bones, Tools Fo55il Leaves Afammals in California /iilarine Shells team. Trees 3c. sea Shells Scdphites Baculites Sea Shei/s inocergmus oyjters Leai^es of Trees Dinosaurs Colo. SeaSheits/nl^o/mng fwtprintsofJdurtans Land Plants Corals Sea Shells^ Spin fers,etc SeaShetts Fish Corals JeaShettj Crustacea Tri to bites Corals JeaMb FetvPostttve J/g/7sofLtFe Plate VII. Prospectors' Geological Table of Wesiern Formations, Showing Principal Characteristic Rocks, Minerals and Fossils to be Found in Them. i: \\ I 38 li Fossils to a geologist arc the labels of the rocks; show a geologist a fossil, and he will probably be able to tell at a glance whether the fossil came from a series of Paleozoic, Mesozoic or Ceno;:oic rocks, whether it belonged to a ver}- ancient geological period down near the primitive granite, or to a comparatively recent one near the modern soil, high up in the geological scale and nearer to the life of the present day. He mav be able to tell not merely whether it belongs to one of the great divisions, to the great eras, but also to the subdivisions of these eras, whether to the Silurian or Carboniferous, the Jurassic or the Cretaceous, or even to minor divisions of these, called groups ; whether, for example, it belongs to the Dakotah group of the Creta- ceous, or to the Laramie group of the same period. PRACTILAI- USE OK FOSSIL.S. The practical use of a general knowledge of fossils is obvious. A prospector linds in certain strata a fern-leaf of the Carboniferous, this tells him he nmst be on the coal strata and forthwith he hunts for coal. Or he linds a Paleozoic shell or coral which points to the fact that he is probably in the neighborhood of the precious ore-bearing rocks. Later perhaps he finds a shell or ccal characteristic of the lower Carboniferous blue liniest. " te Plate IX. -Silurian Fossils. I. 2, Orthis ; -^ 4, Spirifer ; 5, Pleurotomaria ; 6, Murchisonia ; ja, ji, Trilobite (Calyniene) ; 8, Coral Fenestella ; g, Coral Choetites ; 10, Graptolite; II, Orthoceratite. of which the stems of the sea lily are composed, are some- times very common in Silurian and Paleozoic rocks, though it is rare to find a complete Crinoid, and especially the beautiful comb-like flower or head of the sea lily. He is likely to find also a more advanced type of the Trilobite and various Spirifers and other shells as pictured. Plate IX. I \^ I. i 42 DEVONIAN. In the Devonian he may fnul the teeth or bones of fishes, and a tew remains of pcciiUar land phmts, neither of which are known in the Silurian below, also many corals. Plait, X.— Devonian Fossils. I, Spirifer ; 2, Comoc.Trdiuin ; 3, Orthis : 4, Goniatites ; 5, 6, 7, Corals ; 8, g, 10, Fish 'ieeth ; 11, 12, Fish Scales. CARBONIFEROUS. In the Lower Carboniferous "blue limestone," corals and shells appear, especially vSpirifers and Productus, together ■with Crinoids and a \ery simple curled shell like a snake coiled up, a " Goniatite," one ot the earliest of the Ammonite class. At Aspen, associated with the ore deposits we f(nind in the blue limestone most of these, tcjgether with a kind of snail shell called Pleurotomaria. At Leadville in the same ili 43 lonnation Spirifers and Productus are occasionally found. A very curious C(jral is one shaped like a screw, called Archimedes, alter the author (^f the screw. Cup corals are common. , ic, Productus; 2, 2, Spirifers; ;:i, 3, 3, Rhyiiconell.-i ;_ 4, Euomphalus ; 5, 5, Crinoids ; 6, Pleurotom.iri.i ; 7. Bellerophdii ; 8, Athyris Subtilita ; g, Astartella ; 10, Ocmiatites ;_ 11, 12, Corals; 13, 14, 15, 16, Plants; 17, Spine of Echinus. there is a general family likeness between the fossils of each division of the Paleozoic and in the Paleozoic as a whole, and it may not always be easy for him to determine whether a shell is Silurian, Devonian, or Carboniferous, but of one thinjT he will be certain, that it is Paleozoic. IP! ^l % i III 44 TRIASSIC. In the Trias throughout the West, he is not Hkely to find inanv fossils, the locks are generally too coarse, but in the Eastern States, though he may n(jt find any true remains, he mav observe the tracks left by great Saurians, as they walker! on their hind feet, or on all fours, on the red sands of the beaches of those dreary salt Triassic seas, leaving " footprints on the sands of time " full of interest. JURASSIC. In the lurassic shales and limestones in Colorado, he may be equally unsuccessful, though in the upper Jurassic just "^^yx PlATK XII. — JURA-TRIAS FOSSILS, 1, Dinosaur Lizard; 2, 3, Foot and Shoulder Bone; 4. 4, Vertebra of Sea Saurian, Ichthyosaurus ; 5, 6, 6, Teeth of Saurians ; 7, Belemnite ; 8, Echinus 9, 9, Ammonites; 10, Exogyra ; 11, Trigonia Shell. below the Dakotah sandstone, he may light on the bones of gigantic Dinosaurs, or great land lizards, such as the author found in Colorado and Wyoming, monsters 60 to 80 feet in length and proportionally tall, standing from 20 to 25 feet in height. In the lower Jurassic in Wyoming, he will find great numbers of sea-shells and Ammonites, and a 'round 4S shell like a cigar called a " Hclemnite " or spear-fiearl. thc- internal shell of an ancient cuttie tisli. Plate Xll. CRETACEOUS. In the Cretaceous, bej^inning with the lowest group, the' Dakotah group, net-veined leaves of deciduous trees, such as the willow, a — n T" a .§ VI ^ 7i % 1 V n o H I •0 > I > s r. ■0 ^ T* ^> X u vi rt s* y ■J. 3 - % ^ ^5? r. t^S U' OS ^ is^ > D -? n ii-a > ^=r •/ r. ?r - o "T" c PC n o (~ &5 r. i^ J. W X p t .^ r» K (^ tt; P •a ^ ^ M c a ncss is amongst rocks. He wants to be able to recognize them at sigiit, when he picks up a loose pebble, or confronts ! ; ■/% //..■ "'^^vc^/' rr^" X v. t^" >< //\ ^ •^ ;• ^/. V. ■v-i -v^i u: y ;j »- ■C i!'- X. < rt ■J rt H- /— « '^^ ^^ > c ;?; *-^ ^- «J w-> u ^^ 5 y: /- rt < u- C/) o ■c o •/. >'-^ c y a K* E X c a mighty cliff. When travelUng ON'cr the mountains, as he sur- veys the grand panorama from the top, he wants by the pecuhar forms and patterns' each variety of rock is apt to take as the re- sult of erosion and weathering owing to different degrees of hardness, to be able to make a shiewd guess from a long dis- tance, as to whether one moun- tain is made of granite, or another of limestone, ^r a third of por- phyry. This liabit of forming rough guesses as to the charac- ter of distant rocks, decides him as to choosing his course for prospecting. " In those sharp granite looking peaks " he says, "may be 1 will find fissure N'cins. Yonder cones, like the spires and minarets of a Gothic cathedral must be porphyrj' or igneous rock, another likely localit}', and mark where they break through the sedimentary strata, and tip them up ail around them ; at the junction of these sedimentaries with the igneous rock, there may be lime-stone, and a ' contact blanket deposit." Von smooth grassy slopes are probably under- laid by sandstone or limestone, and the rolling valley beneath by soft shales. The latter are un- promising for precious ores." Or. again descending from his perch into the canyon below, he recog- nizes the granite basis, and on top of it, a series of sedimentary rocks. The lowest of these, by its rust3'-white, masonry-like struc- ture, lie judges to be Cambrian (piartzite, the thin-bedded strnta above, Silurian limestones, and ^^ 49 the heavy massive beds above these, Lower-Carboniferous blue-limestone, whilst a dark greenish-gray rock, running in and out irregularly among the strata, sometimes between sr N u 3 r > X en r n V n 3 > >■ >* ^ S. '-^ V mU, r/z "7 -r Sp >.u *^ S *-• ^ N -■ s- p*^ . ' ►-re -*•-. " r X r. ^ C ^ 5S X X >>.- u- - i> ^3 X x ^',1 pr: "— ■ /« y. HO'" ^ -^ TJ^ X 3- M» 1 r- — .— . J c. -^ • * n ^ n •^ n t-H p MH ►1 V ^ o ,^. 3 T" n o c > X ^ =■ t: ? X S^ LINCOLN I^HlTt P the stratification planes, at others cutting across tiiem, he judges to be an intrusive sheet of p(irjihyry. and looks again f(jr "contact deposits." A rock running up like a low wall from the bottom of the canyon to the top, may be either a ;o -! i quartz fissure vein, or a porphyry dyke, and well worth ex- amining. There are manv ways of studyinj^ rocks, one br hand specimens, findinj,^' out 'all the minerals composinf^ them, and then naming the rocks from which they came; another bv observing the appearance of large masses of u>c' '• M the field, and noting their mode of occurrence; an.i la.Jy if we wish to be very accurate, making thin microscopic sections and a chemical analysis, but for the average prospector these last will lie rarely necessary. If a prospector bought a manual to study rocks, for prac- tical purposes, he would find himself amongst a sea of names of varieties of rocks, nine-tenth of which it is safe to say he would never meet with in his field experience. To sa\'e him the trouble of wading through such books, we select just abcnit as much .is a p-rospector is liable to meet with in the field or find practically useful, saying little also about such common rocks as ;ire familiar to e\ery one. Those that need most deliniti almost any greenish rock of a schistose and soft decomposed char- acter. Cai.ci TK is carbonate of lime crystal, the element of lime- stone, and is distinguished by softness and effervescing in acids. DoLOMi rE or carbonate of lime and magnesia is very like calcite and is the element of dolomitic or magnesian lime- stone. Doh^mite effervesces with much greater difBculty than true limestone. To effervesce, the dolomite should be powdered, and the acid heated. ( f 52 fivi'SliM 01 sulphate of liiiK- can Ix: Histiii^niishcd l>v its i-xtrcine softness, hcinj,' scratched hy the lin^u;r nai ; it riocs not cHijrvesce hue Mnic. HAKiiKor "heavy s[)ar" oc- curs in some veins, hut not as a constilnent of rocks. it i()(>l('l:isc l''«;l(t^l);^r. 3. Carlsbad Twins Kf-Mspar. 4. Aii^ilc iir I'yniXL-iie, 5 and 6 llciriiMeiidc. 53 from porpliyries aiifl other if^neous njcks, in the fact tli.'it its crystals arc all jumhicfi up and cnishcd toj^cthcr like loaf-sugar, and none of the crystals are s<:t like plums in a [jiuldinj^, fiistinctly in a haf;kinj.f or paste of very small ( rystals of amorjihous or j^lissy mat(;rial, as in th<; [jor- phyries or ij^neous rorks. (^ranitt; is probably tli- olrjest and deepest rock known, it is often fraversed by sparry veins, bearance. (jneiss is (jften curiouslv i-m.atkxxii. =*'"' pr'jtt'iy i^'i"''*;'' :'' streaked by seams of mica dove-tailing into each other. If mica preponderates, it is called "mica gneiss," if hornblerule " hornblenrlic gneiss." ScHlS'i' :-.,.iy be "ailed himinatefi gneiss or granite, being fin- ally di^iflerl into htn.ina or leaves. This foliated structure is rinetothe arrangei;u,'nt oi the flat-lying crystals of -nica or GnCI 5 I CoHTO/^TeoMicn Schist Pi. A IK XXI 11. m- ! .? N !i III hornblende largely composing it. It may be a mica-scliist or a hornblende ..chist. Slatk is shale altered by heat into a hard crystalline structure. OUARTZITE was originally a sandstontiC()mj)osed of quartz grains, which by heat have been partially fused together at the edges, resembling granules of tapioca in a tapioca pudding. Ouartzite dififers from quartz in being a rock made out oT pieces of (juartz, and not the original mineral itself. (Juartzite may be white like sugar, grey, brown, or rusty. It shows a true stratified structure. Marhi.k is limestone similarly changed to a more crystal- line condition. Serpf.ntine is a arreen magnesian rock, sometimes ffjund with marble and igneous rocks and is formed by alteration of certain minerals in the latter. CRYSTALLINE IGNEOUS OR ERUPTIVE ROCK.S. These are rocks which are supposed to have been thoroughly fused or melted in the bowels of the earth. Some reach the surface by fissures or volcanic vents, others have nevet attained to the surface or overflown it. but have intruded themselves between the weak places in the underlying strata, or have collected and cooled deep down below the surface in great molten reservoirs called " lac- colites" or lakes of stone. When these have been subse- quently uncovered by erosion, they may present the forms of considerable mountain masses, like the Elk Mountains, and Henry Mountains and Spanish Peaks. Geologists distinguish those rocks which have pcjured out on the surface from craters and volcanic vents as volcanic rocks, whilst those cooling below are called Plutonic. INTRUSIVE PLUTONIC ROCKS. The component minerals of these intrusive Plutonic rocks, such as are commonly called porphyrin's, are principally quartz and feldspar, with mica or liornblende. In color these rocks are some shade of grey, green or maroon, or even white, but their most striking characteristic is .i general spotted ap- pearance. This arises from more or less large, distinct, perfect- ly formed crystals of feldspar or quartz, set in a finer grained crystalline paste or background, standing out distinctly from it. This base or background may be comparatively coarsely crystalline, hnely crystalline, or so finely crystal- line, that the crystals can be discovered only by a micro- 55 mrnmm W'v-i^ scope, whilst the larger crystals seem set in the paste, like plums in a pudding. In the depths of a mine the por- phyry is commonly much decomposed by water action or mineral solutions, and even passes into a clay or gouge. The characteristic spotty appe.irance. from the presence of individual crystals of feldspar may even then identify the rock, or by chemical analysis the very aluminous character of the decomposed rock may determine its character. When feldspar is the main constituent, it is called a felsite porphyry, when a certain amount of quartz is present a quartz porphyry. QunRTZiTEifMrNMOHmco) UiORi IK, whose crystals are sometimes pi^^TE XXIV. porphyritic in character, hence called por- l^hyritic diorite or porphyrite, belongs also to this intrusive or l*lutj;^reen " or cavity lined with ([uartz or otiitrr crystals. An assay from sncli picked s|)eciinens would fj;ive a very uiitair aver- -^-^^^v v^ aj.(e of a mine or prospec* The hulk of the profits of a mine come from the coiiimoiier minerals such as j^al „:* I I I i I c ii. DECOMPOSED MINKRAr.S. Sometimes the franjj^ue matter contains a \ariety of de- composecl ore in rich seconflary coir- l)inaf ion inti'nately mixed through its mass and rarely n. ^ernible hy tho eye. Thus yellow mufl from a mine mav assa) hijj[h. from the presence of inxisihie chlorides or su1j)hurets of silver. No accurate estimate of the \alue of a mine, or even of a piece of ore, can he found, without an assay or mill-run. The reason for such richness in decomposed surface products, is, that nature has been for ajj^es leachinjj^ out, concentrating' and C(jml)ining in richer forms, the essence, so to speak, of the \ein. Grav CoiM'KR (Tkirahrdritk). Besides the ordinary f^alena and pyrites common in most mines, we sijinetimes lind con- siderable bodies of ^ray copper in mines, or intermingled with other ores. This is generally a rich silver- bearing ore, running from 60 ounces to some thousands per ton. It gen- erally occurs massive, rarely show- ing its pyramidal " tetrahedrite " crystals. In appearance it is not Pi A TK XXXV unlike a fieshly broken piece of ' ,., I ,'. , bronze. It is more common in fis- Oray Copper Uertrahednte.) ^^^^^ ^^^.^^ .^^ ^^,^^.^^ and CruptiVC rocks than in limestone. In Halls VaUev. Colorado, it is asso- I :i^l ■Mflu^ail riia^ 62 t oiatcd with baryta in a vein in the gneiss. It occurs in the (icorgetown veins in granite. In the San juan district it oc- curs also associated with baryta in the Bonanza mine ; and an ore not identical with it in'coniposition. but very like it in appearance, called bisniuthinite, consisting of bismuth, anti- mony, copper aad silver, is characterisfc of that region and is rich in siKer. lUsmuthinitc has a more shiny tin-like appearance than gray copper, and the red color which bismuth gives to charcoal under the blowpipe readily dis- tinguishes it from gray copper, I.OCAI. VARIA I HiNS IN VAMK OK ORES. There are locally in dilTerent mining districts considerable differences ii. the \alue of (ertain minerals and ores. In one district gray copper may rarely exceed 60 ounces ot sil\-er, in another it is invariably o\er 100 ounces. A coarse galena is generally ]V)or in siKer, while fine grained " steel galena" is generally rich in siKer, but the reverse may also be the case. \\\ some (jf the mines at Aspen, fine graineri galena, especially near the surface, is quite poor in siher, while in other mines in the same dis- trict it is exceedingly rich. Localities occur also where coarse-grained galena runs well in silver and is richer than fine-grained galena. This is the case at the Colonel Sellers mine at Lead\ille. So one mining district or even one mine is not a rule for another. PvRiiE.s. — Iron pyrites and copper pyrites, common in most of our quart/ veins in granite and in the eruptix'e rocks, mav y!eld both gold ami siKcr, but usually tlx? former. There are certain districts more characterized by pyrites than others, such as the Central City district. These are gener.;liv gold-jiroducing districts. Some of the mines at Hreckenridge and South Park have strong pyritiferous veins in erupti\e dykes, such as the Jumbo mine. These have of late produced a great deal of gold. The sanu' dis- trict, however, jiroduces large argentiferous lead veins. Pyrites generally fa\'or the granite, eruptive and crystallized rocks. The cpiartzites of the Lower Silurian of South Park and Ked (^liff are often |iyritiferous and generally gold-bear- ing. In limesti.ne the pyrites is rare or absent, its place being tilled by some form of iron o.xide. In the deeper mines of Lead\ilie. however, this iron oxide is beginning to pass down into the iron sulphide or |)yrite from which it was derived, Iron pyrites can generally be distinp'.ished from «apn ' 63 copper pyiitL's by its paler, more brassy color, by its superior hardness and by its crystallizinainder being chlorine. As a seccjiidary product of decomposition it is generally found near the surface or in cavities, sometimes deposited on calcite or other crystals. In the mines at Leadville it is commonly associated with other decomposed ores, such as carbonates. In the Chrysolite mine, a mass weighing several hundred pounds was found. Chloride, bromide and iodide of silver are closely related, being com- pounds of chl(jrine, bromine, iodine and silver. It is notice- able that these salts are the elements of sea water, and that these ores are often found in marine limestones. Accord- ing to Mr. Emmons, the change at Leadville from sulphifle to chloride was produced by surface waters; these waters are found to contain chlorine, which they probablv derived from passing through the dolomitic limestones wiiich con- tain chhirine in their crystals, and these limestones perhaps originally deri\ed it from the sea water in which they wt-re deposited. Chloride of siK-er is found at Aspen aiv! abunrl- antly in the outcrop of mines in New and Old Mexico. .SULPHARSENITES. Rrnv Silvf:k (Pynirgyrite and Proustite). Composed of sulphur 17.7, antimony '22.5, silver 59.8=100. Crystallizes in rhombohedrons. is seen in spots or crystals on ;i mass of ore of a deep red or blackish tint. When scratched with a knite it shows a bright or deep red color. In some mines this very rich ore occurs only as specimens, but in others it is present in sufficient (juantity to largely influence the value of the ore in bulk. In parts of the (iianite .Mountain Mine in Montana, it constitutes the principal ore, associated, however, with other mineral. It there occurs in large masses and accounts for the extraordinary richness of th;it celebrated n)ine. Pnnistite is much the same, only lighter red, and consists of sulphur 19,4, arsenic 15.1. silver 65.5 = 100. 65 CARBONATES. This term also embraces a large family, the commonest being carbonate of leau (cerussite) and carbonate of copper, (malachite and azurite). CoppKR CARBONATE Can never be mistaken, owing to its brilliant green and azure blue color. Copper stains are among the common surface signs of a " lead. ' It is gener- ally associated also with rusty stains. Both are the surface products from copper and iron pyrites forming a vein below ground which may or may not be profitable. Copper stains are common enough in many rocks, but do not always lead to bodies of ore. In South F^ark the red Triassic sandstones are sns of the fissures, as certain sublimed mineral vapors fn^n a smelting furnace sometimes collect and recrystallize in the flues. By many prospectors every indication or surface appear- ance of a 'vein, or even a likely-looking rock, is called "a blow out," a term suggestive, at least, of some sort of vol- Platk XXXIX. Fold Passing into Fault SHowing Hrokcn Characrcr of Fault Fissure and Adjacent Rot-ks Prodiicinjj Later a Brecciated Vein and " Horses." canic explosion at that point. With them, the " fire and brimstone " origin of ore deposits ii> as deep seated as the veins in the rocks. These ideas contain a measure of truth, and were naturally suggested by observing that our ore deposits are so generally associated with volcanic rocks and evidences of past heat ; and it cannot be denied bui that the presence of these vol- canic rocks had more or less to do with the ore deposits. The modern study of ore deposits inclines to the belief that we need not draw directly upon the unknown prof.)und supposed ignited regions of the earth's interi(jr for the direct source of metals found in the veins, nor entirely from \'iolent explosive volcanic agencies, nor from very intense heat, but i.i« ^^-^^^ 69 Platk XL. A Tight Fault Crevice Being Attacked by Solutions Producing Finally a Narrow Fis- sure Vein— Small Dois = Ore Solutions. rather that \vc may lotjk nearer home lor the immediate source of both metals and veinstone, namely, in the ele- ments of the common country rock adjacent to the ore deposits; and for the me- dium of distribution and concentration o{ ore and veinstone from nothing more violent or volcanic than water, more or less heated and alkaline. Nor is it so absolutely neces- sary to suppose that the tilling of a vein fissure with quart/ or metal must needs come up from pro- found depths, and from a foreign source; but (juite as likely from the adja- cent sides of the fissure, or even from abo\'e the position later occupied by ore. Veins of whatever kind are not vents for molten volcanic matter, but simply courses for water, more or less heated and alkaline, in fact, channels lA mineral hot springs carry- ing earthy minerals and metals in the same solution, and depLATE XLIV. Jointed Slate. Pt'*-Au.w««Wrt - irwww^^w:^.- •«iw«p«K)n!>tw«yt^iw>m)»^iif 71 or later eaten out. so to speak, and replarcfl by niiiu;ral matter. Some of the broken rock beinjj^ not conaumeci in this way. was left, forminjj^ fraj^^ments in the \ein which when small are called " breccia " and when larjije " horses." The ^reat " jj^ash " tissurt such as we find occupied by so aV ' lissure veins in volcanic shoe such as those of the Sa\ hi;.- rejj^ion, Colorado, appeal ' > L ' due not so much to fj[reat ear'*^ nio\'ements like the last, as toop.. niu^s formed by c<;olinj4^ and nfaction of the lava, somewhat .. .1 ay be obser\'ed ., v|i,XTV on the cooliiif^ of iron in a slajj^ furnace. Ore deposits of lead and J"'"''' '" Coiumn.ir Hasalt. other minerals lorminjj; bedded deposits in limestones find their way in solution throujj^h the vertical joints common to all water formefl rocks, resuitinj^ fronj^ contraction in consolidatinjj[ from a soft, muddy condi- tion. Such fissures are short but they act as channels to a more important line of weakness occupi- ed bv the main l)od\' of the blanket ore deposits, viz.: the d i V i d i n^ line be- tween one stratum and another. An- other line of weak- ness for the attack of mineral scdutions is at the juncture of a porphyry sheet or dyke with some other rock. The interval between them is often occupied by a "contact vein." The heat of the \'olcanic matter tojj[Cther with steam may have influenced the solutions, even if the porphyry did not actually supply the metallic element in the vein.' f'o/t/rtrf Platk XLVI. Contact Ore Deposits I{ct«.-ecn Porphyry .md l.imestcinf. n^I.DINd AND FAUI/nXCl. In the many and ^xc\\{ upheavals of the earth's crust, re- sulting in ccjutinents risinj.^ abo\e the sea, and on those Ill '! ft* n continents still greater and sharper upheavals forming mountain ranges, rocks have been much broken and frac- tured, from great fractures, forming fissures miles in length and depth, down to little cracks of but a few inches. Much of this fracturing has been caused by the folding and crumpling upwards of strata into mountains, accompanied bv great crushing and mashing together of the rocks. When this lateral tangential folding and compression of the rocks reaches its maximum intensity, the rocks break, and a fault or slip is the result, with its attendant fault-lissure. This relieves the strain for a while, but the shock, doubt- less at the time accompanied by earth(|uakes on the surface, resulted in a general breaking up of the arljacent country into many parallel and smaller faults and cross faults, be- sides a general shattering of the ground intermediate to the faults. A region thus faultefl and shattered is )ust in the desired condition for forming a future mineral belt IS RoiKS. When these fault fissures descend to a \-ery great depth, they may tap the molten rock reservoir supposerl to lie be- neath great mountain ranges, and the molten lava or porphyry, rushes upward through the weak line of the fis- sure, tills it with its matter, wliich on cooling becomes a dyke instead of a mineral vein. These eruptive rocks may (jr mav not reach (piite to the surface and overflcnv it in a lava sheet. H they do not. they find relief by intruding themselves laterally between the layers of stratified rocks, whose leaves or bedding planes may have been partially opened, like the leaves of a crumpled book by previous action of folding. In such cases the por[)hyry dyke or in- trusive sheet may, if it be mineralized, answer all intents and purpose of a mineral vein, or the ore may be found on one or both sides oi such a sheet, in the line of separation and weakness between it and the adjacent strata, or it may permeate and mineralize by a "substitution" process an adjacent porous or soluble rock such as limestone. Thus both in the dyke or intrusive sheet itself as well as at its contact with other rocks, the pn^spector should look for signs of precious metal. If the dyke or sheet should be decompijsed, clayey and 73 rusty, it mav contain free gold disseminated Ihnjugh it, which, at a depth which may or may not be ever reached by mining, passes into the auriferous iron-pyrites from which the free gold originally came. In this case the ore will be no longer "free" or "free-milling." but of a charac- ter that must be subjected to the more expensive treat- ment of roasting or smelting. Little stringers «jr veinlets of quartz, if observed in sucli an eruptive rock should be carefully examined ;•.:; the most likely source of the richest gold ore. Som«; of our most noterl gold mines in the West are in these "rotten " mineralized dykes or erut)ti\e intru- sive sheets. "Likely signs" in such would lie rusty "gossan " stains of green carbonate of coj)per and gouge or clav matter. It is W(jrth observing that the dyke may be only valuable as a mine as far down as the decomposition lasts and as long as the ore continues in a free state. Witli depth, the pyrites of the undecomposed lower portion of the dyke mav be found too poor in g< 'Id to pay t(ir smelting e\en. As this desirable state of decomposition is the result niainlv of the actiI.ATK XLVIII. Prospecting with hiamoiul l>rill<. sometimes ad\ aiitageouslv be done bv dr.lling with diamond drills lioni the surtacc down through as many of the strata as are suspected of being ore bearing, the "cores" brought up will show if an ore bodv has been penetrated together with its apptoximate thickness at a certain point, and if this process is Continued over a certain area, tne approxiniate areal limit of the ore body may be ascertained. This work may follow upon a close examination t'lrst of mineral signs along the outcrop. It is sometimes done after an area has been exploited for some time bv actual mining with a \iew of fiisco\enng new bodies or continuations of the ore. n TRUE FISSl'RF. VEINS. Whilst profound fault cracks may be filled by lava, those not dcscendinjj; to such great de[)ths (Unibtless lay open, till they were gradually filled by solutions carrying in earthy \ein-stone and metallic matter; in a word they were the channels of mineral or hot springs. It must not be supposed that these fault cracks were ever " open chasms " commen- surate in width with the wide dvkes and veins now fcnind in them, but rather in some cases very close fitting cracks, mere lines of weakness, the walls anpressed closely to- gether by prodigious lateral pressure. In other cases the fissure would be rather a shattered /one passing down through the strata, than one definite line of fissure. Doubt- less when the molten lava ascended through these fis- sures it greatly wirlened them to admit of its volume. In the case of true fissure \eins, the fissure or shattered xone was enlarged by the corrod- ing, substituting power of acid mineral solutions till we have to-day a fissure \ein twenty to fifty or more feet in width. In the shattered zone, this substituting process would go on easily and rapidly. Pi ATK XLIX. I>recciated Lode with Quartz Geodes. IMAIK L. iUecciatcd Vein. until nearly mineral i rly all the shattered fragments were replaced bv natter excef)t a few " imligestible " pieces, which if 78 ■small, would cause what is called a brecciated vein, and if llarge, " horses " in a vein. These fragments are not so much pieces that have fallen from abo\e into an open tissure gradually lilling up with solutions of (juartz and vein matter in which they became entangled, but rather undigested, lunsubstituted fragments (jf the wall rock, immediately .adjacent to the fra"^monts, for at times stjme line in the .fragment corresponds to a line in the adjacent wall rock -without evidence of any serious displacement. Again, the ■shadowy outlines of fragments can be (observed partially but not entirely replaced by quartz or vein matter. Some- times the " breccias" are surrounded by rings of (|uartz or inetal and called "cockade ores." i\ HOR.'^K.S. In the San Juan region in Colorado, where we have won- derful opportunities of obserx'- ing extensi\'e sections of great fissure veins descending the faces of clitTson either side of a canyon for two or three thou- sand feet, such broad veins at inter\-als split up into two or three arms enclosing large frag- ments or " horses " oi" the la\a country rock, and again unite to f(jrm the main vein. These veins occupy a once shattered tissure, the walls (jf which were origi- nally neither straight nor regu- lar, \, t shattered and cracked. The vein matter insinuated itself between the shattered portions, sometimes fonuing a " breccia " of small fragments, at others " horses " of large ones. The appearance of these great San Juan veins from a little dis- tance is that represent- Vein n Faulted by Cross-Vein B. ing the fallen or risen side of a fault block. These fault lines should be carefully ex- amined for mineral indicati with (lay. itibbish and broken rock, or tin* two walls may be actually wt'lded toj^rrther by pressure accotn- panied by a <-ertain anw)unt of heat, producin/i,' local meta- morphic action. l-'aultiiij.^ Joo in some reg- ions mav have occurred - parati\('ly recf lUly, or at least altiir ihc period most marked .| by deposit of mineral solu- X lions .1(1.1 ore deposits, in ;;^;^ which c.fse tin; fissuies may 1-5 •- be I'l'vrtMi or at. ptesent occu- pi«Nl l)y hot or mineral springs making' \eins lot the luture. A stupendous, comparati\ely njodern faelt, runs alonvj the west base of the Wahsatch mountains in ( 'tab, its line is m. liked l)\ a S'-ries of hot sprin).;s. Aloiij^ the lace of a c.in- yon wall the piosp«'ctor may notice some peculiar stratum near the top of the dill and its counter[)art out of placj' near llur bottom, showinj.,' that a fault has oc«Mirred. whose amount of slip he can easil\ estimate di measure ; but when a fault ol many thous- ands 1)1 feet occurs, a knowi- (•(Ijjj,' 1)1 the flifferent j,^;«;olojri. I a! periods in\'o|\e(l in the slip is necessary to estimate the amount of lall. I'liiis il ■3 U c c U. 3 r* u V "3 n 8i a prospector by his j^eolof^ical kiiowlt'rljrt; should rc('o)>;nize a ("rctacoous rock hrouj^ht up jn jIosc juxtaposition to a Sihirian rock hi; wouM know that a stup«'twlous taulf ha(l occurred at that place, involvinj; the entire thickness ot the rocks comnosinjj^ the |)erio(ls inlerveriinj^ between the Sil- urian and tlie Cretaceous. Tliat a faulted rejj[ion is one in which j.;reat toUlin^ due to lateral tanjj^ential prt-ssure has taken plac«'. th«' folds event- ually l)reakinj.»(lown in faults, is well seen in tin* structure of the .Mos(piito r ■ anj.je in South Park. Colorado, which embraces the Lead\illf inininjj; district. Tlu' comparatively hoii/ontal strata ot the I'arkasthey a|)proach the .Mosquito Kanj.»;e brf^in to told j^'Mitly. thf folds jj^raduallv increasinj.( in steepness and closeness as they a[>- proach the a.xis (»f the ranj^c. As we pass up I* our Mde Canvoii. which shows a com|)lete cross s.-ction ol thv ran^t", we tind the axis to be formed by a maj^inficent aiid very st<'ep arch, well shown on tin- f;!ce of Sheep Mountain, which ha\inj.>[ arrived at its utmost tension h) i-aks down in what is called the London mine lault, »ra\'ers'U|ij and split- ting the ranj^e lor twentv miles. 'I'he line ol the fault is slidwii b\ a di'pression bet ween Sh»' 'p and Lamb .Mocilain, In nearly «'\ery canyon alonjj^ tlie ', ii»k ot •'us ranj^'. the line of the faidt is easily traced by siisiilo arches and '■ sa^s ■ .ind by a prcidiar wa\v loo,, ol the Mule of this raii^'c down into i .id\ill«' and Ihf Xik.-iisas \'a(ley l)y a series ol ^ij^^antic steps or ben^hrs. e.u ji bench lepresenl- inj^ a tallen faulted block. I''aults have thi-ii |)oints ol maxinuMn dfplh and (list urbance. from whii h the\ aie a|)t to die out at chrr end in folds or rounded hills. iteat faults are acconijumid by minor parallel and cross faults. The idtiiiiati; tauseofthis folflin^ ;Hid faidt in^ is ;it I rib- uti'd bv souje j.(eoloj.>[ists to the inttnioi ol the earth j^rowin^ colder aufi contracting. causinj.j tiie surface crust to shrink and fold in adaptinj.^ itstdf to tlie shrinkin/^f interior. IMo- fessor |. K. Kemp sa)s : "The strains induced i)y coolinj.; and contraction of tin; earth are the ujost in>p<»rlitiif caus«' of fraclnre. Tin- contraction (h'\tdops .i i.injrcntial v,(i.iin which is ri'sisted y t he aifh-like dispr>sition ol thecni-^t. Where ther>' is insutlicient supixut. 'gravity causes a s ij^r- j{inj.( ol the m.deiial into t rou^fis or synr ;ii)f iclinal (nWls Ixiwrrn them. WIric tlit laiij^i-iit iai strain is j^ncak-r than tlie abilitv of the Kuks to resist, they arc u|)s«t and cruinplrd into folds ti.iin (he tliiust, Hofli kinds of l<,lds inc fnntfnl causes of liSMurinj; cracks and j^n-ncral sllat(^.•rill^^ and c\cry slif) from vicldinjL,'- sends its oscillations abroad, which cause breaks aloni^^ alllincs of wti'kness." its, cnmnioii Id ail ricks, a|)])car to he dne not so much to faulting and motion, as to shrinka>,'e o! the locks in p.issinj.,' from a soil matl<'r or nuuldy condition to one of ( oiisolidatioi). A j4;ood manv so-called lissiire \fins, v\vi\ in the j,,Manit<' serii-s, appear to occupy extensi\'e joint crac ks, rather than lanit planes. These may he due to the general shriidiaj'e of the whole mount. un mass in consolida- ting^ from a sum; (»lastic or a«pieo-i^neous state ol soften- in;,,' to one more consolidated and ri^ifl. The joints in l.iv.i sheets lomiin^^ curious columns like tiMJse ol IIk- I'alisafles ot the lliulon are flue to the same shriMkay;e lr i|o- mitic. At Kead\ille the deposits occiipN part of a si'ries of faulted anti- clinal arches and syn- clinal t roii).>hs. ol whiih tl;e Mosipiito ran).je is the main .i.\is. The heds lie hetweiMi didomitii" limestone and sheets of |)orphvr\. The ore heds partake of all th«' foldinj^, faultiny^ and olher contortions which the enclosinj^: rocks ha\ e sntlercd in the uplie,i\al ol the moun- tains. The thickness of such deposits \aiies much and may gradii.illy thin out and disa|>piMr. hul mav also ( ontinue loDf^; enough lor all mining purposes. ()ften lliere are no sh.iip limits between an ore hetl .md the enclosing- rocks, oi helwern the oic hed and the walls, it walls exist at all. The ore appears to imjtre^nate tlie sur- rounding; rock l)\ .1 ( lu-mical inten han^e between the elements ol the rock andllieor*-. Such .1 " met.isoiuatic " interchanj;*". " siibstilutioii, " or • leplactinent " appears to have taken place in the .iij^enlileious le.id deposits ot Lead- ville and ,\spen brlween the ore and the limestones. According to riiillips. •• .1 true ore bed never product's a 'Combed' 01 'ribbon structure m.idr up o| symmetric.il IM.MK MV. Kiiiillcd Ore-liedH in Antii.'liniil aixl Sviuliti.il 84 h : i| II ■n 4i layers, such as is comiuun in so-called ' true fissure veins, and is usually without the crystalHne texture observable in veinstones." INSI KATiriKli DKI'OSns. USSIKK VK.INS. KTC. MifJeral veins are chan^Hahle in character, and their ap- pearances of a perplexinj4 and complicated nature. There IS a j^'radual passage from one form to another, so that it is diflkult to classify them. There is often no such sharp dis- tiiKtio.i between one form of ore deposit and another, as lej^'al disputes would sonjetinies demand, and a witness should hardly be called upon to assert on oath tha« .such a vein is a ' iruc fissure." or another a "bedded \'ein," or a third a "iegregated vein." " Nature abhors straight lines ' anfl sharp »Mstinctions, and delights in blending one form i;Mperce()tibIy with another. I*hillips di\ines veins into two classes. " regular and ir- regular veins." " Regular uustrUifiefl deposits iiulude true veins, segngafffi veins and gash \eins. Irregular deposits include impregnations, fahlbanrls. contact and chamber flenosits. " Veins are collections of mineral matter, often closel)- related to. but differing more or less in character from the enclosing country rock, usu- ally in fissures formed in those rocks after the rocks had more or less consolidatffl. All \'eins fio not carry metals; some are merelv l)arren (|uartz, fildspar, or calcspar. like the b.irren veins we so oficn see tr;«versing granite or limestone rocks. \'eins may divide. " split up " or thin out, and are irregular in shape and structure, owing to the irr«*gular width ot the fissures and to other causes. PIAIK LV. A Split Vein, DKII.MTloN (»F MININd rKHIVIS. The rock in whicli a vein is found is called the "country rock." <•.;'.. liinestfMu-. granite, norplnrv. The [xMtions of countty rock in t'linct contact with tlie vein are called respectiv«'ly the "hanging wall," or roof, and the "fool wall ' or floor. This is onlv in inclined or flat \eins. as a vertical fissure vein can have neither roui «$ nor floor, but only two walls, east and west, or north and south, according to the coinnass. The inclination of a vein to the horizon is its "dip. The horizontal direction of a vein at rijjht angles to its dip is its "strike." The latter may commonly he observed alonjj; the surface outcrop, the f(irmer either in the workings ot the mine ()r where the vein is exposed on the side of a canvon. Roth dip :ind strike of a \ein often vary much, the former with depth, the latter with extension across the country. A vein or ore deposit will not unfrecpiently bej.jin with a j.,'entU' dip. and increase rapidly in steepness with depth. The ore fleposits on As|)en Mountain commonlv bej^jin with a din of 25 . and at a depth of less than a thousand feet reach (o or more. As tissure veins commonly occupy fault lissures. their irrefjularities in dip and strike corresp(»nd to those we have already spoken about, under faults. The anj.fle of dip is usually taken from its variation from a horizontal. Mot a perpenflicular line. Thus a dip of 75" means one th;it is very steep, while one of 10' is a gentle inclination. A laver or shee'. of clay called " j^^oujj^e."' or sel\aj.je. often lines oiu' or both walls of a vein between the country rock and the jjangue or \'ein pr(>per. It is deri\i'd from the ele- ments of the adjacent country rock. decom|)osi'd by water, and sometimes by the friction of the walls of the fissure ajj;ainst one another, or aj^jainst the \-ein matter, in the jirocess of sli|)pinj.j and faulting.;. whii"h is often shown by Its being smoothed, " slickensided." j)olished »)r groo\ed. (Joiige often contains some rich decompc^ed mineral in it. such as siilphiirets of silver. It sometimes occurs in the heart of a vein, especially if that vein has been re-opened anew by mowments of the strata. The " riiinese Tallow " gouge of Leadxille results from the dec(tm|)osition of the leldspars in the adjacent white porphyry, and is a hydrous silicate of alumina. ill the granite \eins in Clear Creek County the gouge is (ierixt'd from the feldspars of the grai ite. (iouge is some- times useful in defining the limit of th • \ein between walls, t bus preventing unprofitable exploratioc into the " country." it is alsd a guide for following down a vein when mineral and gangue may be wanting or obscure. Moth walls are not always clearly detined by slickensided surfaces, by gouge or other mark, and s(j at times the vein is lost. *i»«i^i**'«*'«»« I' '1 I hi i 86 False walls, catiscf! by movements in the adjacent strata, by joints, utc. also niisluad. It is not uncommon tor a tissure vein to have but one clearly defined wall, the other, if it exists. bein>f obscured or chanfj^ed by mint-ral solutions. Sometimes two cracks (»r fissures occur parallel to ea« h other anrl the inter\eninvi: country rock has been altered and mineralized into a vein. It is Mobably in this way that many wide veins were tormer . Mr. amnions has fr)und that fissures are formed by jijreat movements of the earths crust .fefl with the proper metals atid veinstone matter and the necess.iry chemical anrl physical conditions existed, the rocks lyin^; between those cracks or joints were altered into ore. As one element was dissoKed anothe-r took its place, so. accordiiif^ to this auth<»rity. it would seeni that e\en a list;ure vein may be only a sort of "metasomatic replacement " of rock by mineral. Hence what is commonly accepterl as a " wall " of a vein, is not necessarily one. and cross-cuttinj.;. in order to determine the lateral boundaries c,f the ore. is safer than to rely on supposed walls. A so called "slip" has often been followed by a miner as a supposed wall, until by accident he broke throujj[h and found irood (ire on the other side. If \eins are formed accordinjj^ to Mr. l-'-mmons" theory, the occasional loss of one or both walls is easily accounted for. Cross veins of a more recent af^e sometimes cut or lault an older vein. The point of intersection is generally rich in mineral. Cross \eins must not be confounded with Pl.ATI. LVI. IinpreiinatiDn of Kock t>y Vein. 87 " leaders, " whiv-h arc tln' iillinj^' ni iniintr cracks rxtoiulinj^^ off from tlu' \i it), anfl ari' sonutiinfs MiHicifiit l\ profit. il)l«' to work. Wliilc llicy somctinifs Ir.id a |)ro>|»«'(tor to the main vein, they may also lead a miner miderj^^romid astray from tin- true \iin. The spliltiiij^' of ;i \t in by .i " horse " or lar>;e frai^ment ol the country lyinj.( in the vein, may he mistaken for a true cross vein, or the orif.;inal fr.ictiire of the fissiuf mav have been in the form of a star or like llie spokes ot a wheel radiat- ing.; to the huh. In such cases there are no true cross xcins. Hut when, as in the San Juan district, we ha\e two well diliiu-d sets ol veins, one strikinjj^ northeast by southwest, and the other northwest bv southeast, they «ut each other diagonally, the cut \'ein l)eiiij.j the older, 'ihesc o|)posite sets ol \eins ha\e been formerl at different times. .M.inv contain a char- acteristically ditlerciit class or \ariety ot minerals. Thus in Cornwall, Kii^land, one set carries tiii and the other K'ad. si(;ns Of' .\ rKir iissi hk vi.in. True fissure veins show si^ns of motion or slip|)inf; on the sides ol the lissure, such as slickeiisides. j,;ou>.je, crushed walls. '• horses," or " breccia," the latter Ix'inj^ small por- tions oj the Country n'ck surrounded and cemente(f by \ein matter. In the Coiii- stock. the (piart/ is f.(round' to powder, riu- vein itself, thoiij^'h occupying.; a healed fault lissuri', may be itself faulted by later movements in the mountain aft»'r the vein was formed. Soiiu- of the lis- sure veins on Knj.;ineer .Moun- tain. San luan, are so dislo- cated. The vein-filled fissures be- \u^ a line of weakness, may be re-opened by mountain movements, ajul other or flif- ferent combinations of ore in- troduci'd into the heart of the vein. Such a reop'jninj,' would be marked by a succession of "combs" or banded ribboti-like deposits of nrv, and by j,j(iuj.je matter. Pi. AT I LVII. Combe Wuu 2.2 M 11= U IIIIII.6 V] <^ n /a ''^. ^%.,^*> ^5 ^ V *>^>^" o^-^ ^ Photographic Sciences Corporation i\ ^^ C V ^ 88 OUTCROP OF VEINS. The outcrop of a vein is that which appears at the surface and usually attracts prospectors to the spot. Sometimes it may be, as in the San Juan district, a bold v^ein of hard white or rusty quartz, standing up in relief, by its superior hardness, above the surrounding countr}^ like a low wall. Or again, in the same district, from being composed ot softer or more soluble substances than the prevailing erup- tive lava sheets, instead of a wall it causes a depression or trough on the side of a hill, forming the pathway tor a rivulet and marked by luxuriant vegetation. Commonly the out- crop consists of a decomposed mass of rock, stained with oxide of iion and streaked here and there with green or blue carbonate of copper, and is called " float " or "blossom " by the miners. This " float " is the chemically changed or oxidized portion of the true and unchanged vein lying deeper below the soil. On Aspen Mountain the float is generally a rough crystalline mass of calcspar and baryta stained with iron and copper. In this "blossom rock" free gold is not unfrequently found, but unaltered sulphides, such as galena or iron pyrites, are rarely mei with on the outcrop. In the San Juan district, on Mineral Point, we have, however, found galena at the grass roots, and broken off large chunks of it from a quartz vein outcropping on the surface. In gold-bearing veins such an oxidized condition is desir- able it it continues down to any depth, for, so far as it con- tinues, the gold is free, and the ore is a free milling one, easily treated, and often exceedingly rich in gold, as in the celebrated Bowen mine of Del Norte ; but as soon as the hard white quartz and the unoxidized pyrites of the true vein is reached, the ore is no longer free milling, but must be smelted. The gold may still be found free, perhaps, in the hard quartz, but if the pyrites should not prove ricn in gold, the palmy days of the mine may be considered as past. Many such rich deposits on the surface, abounding with specimens of free gold, have proved great disappointments with depth. WIDTH OF VEINS. Veins may vary in width or thickness from a half inch to a hundred feet. They also pinch or widen at intervals in their downward course. The widest "mother" veins are nOt always the most productive, though they are very per- ■'a I I 89 sistent in length, and we may suppose in depth also. In the San Juan district the "mammoth" veins of quartz, often a hundred feet wide, are not the favoriies for development, the ore being found too much scattered in them, and the HS ■ .f- > /:•••■ 11'- • '^"'^ ^yfilfciii'^ Plate LVIII. Metalliferous Veins Exposed to View near Howardsville, San Juan, Colorado. Showing Two Systems of Fissure Veins Crossing One Another. development less easy than in those 10, 20 or 30 feet wide, where the metal is more concentrated. These mammoth veins in the San Juan are easily traceable for miles over the surface of the country and down the sides of the deep m I;;' 90 II' [Is : P ' M hi canyons. Their limiting depth has never been reached, and probably never will be by mining. DEFINITION OF TRUE FISSURE VEINS. True fissure veins are popularly defined as filling fissures of indefinite length and depth, commonly occurring in paral- lel systems, traversing the surrounding rocks independent of their structure or stratification, and commonly, though not necessarily, at an angle different from that of the stratification — in other words, cutting across the planes of stratification. These veins originated in fissures, not neces- sarily wide open ones, but on the contrarj-, rather narrow ,. ^^^ cracks descending, however, to great depth such as those produced by faulting, or the general cleavage lines of the mountain. The latter may be frequentl)^ observed in every canyon, and also in the sedi- mentar)' rocks of the foot- hills and even along the flat surfaces of the plains. They Plate LIX. ^re very conspicuous in the Fissure Vein Conforming in Part to plains arOUnd Trinidad, and in p^rfSsing them.^ ^'""'^''''°"' ^^'^ there not unfrequently occupied by a series of narrow parallel dj'kes of basalt instead of by mineral veins. Cleav- age lines or joints are familiar to every stone-quarry- man. These cracks are caused by extensive movements of the earth's crust in the process of mountain uplift, and also on a smaller scale by coi:traction of the rocks in cooling from a heated or molten condition, or even in consolidating from a soft or muddj' condition. The two walls enclosing a vein do not generallj^ coincide, as might be expected, if the vein occupies a line of fault. A true fissure vein may in some part of its course coincide with the dip of the surrounding strata. As the plane of stratification or line of division between one stratum and another is a natural line of weakness, a crack once started would be liable to follow it for some distance. And when uplift occurs such places are liable to slip one upon the other, and a true parting fissure ensues conformable to the prevailing dip. Such a vein might appear at first to belt^ig to the class of so-called "bedded veins," but if with depth 9* it should be discovered to be cutting across the strata it would be pronounced a "true fissure vein." The appear- ance of slickensides or other signs of motion on the walls of the apparently " bedded portion " would then prove it to be- long to the "true fissure" class, and that actual Assuring had taken place prior to the vein-filling. CAUSK OF POCKETS IN FISSURE VEINS. As a fault fissure in its downward course usually pursues a zigzag rather than a straight course with smooth surfaces on either side of the crack, the inequalities of one face of the crack are brought into opposition to the inequalities on the other face, as one or the other side of the fault slips up or down, and thus are produced pinches and wide cavities, which give rise to the "pinches" and " bonanza pockets" so common in fissure veins. A so-called true fissure vein may sometimes have ad- vantages over some other forms of vein occurrence, from its persistency and com- parative regularity to great depths. It must not, however, be expected that it will continue equally rich or equally poor throughout its course. There may be com- paratively barren spots and rich spots, pinches and widenings, local combinations of richer or poorer varieties of mineral. But the vein as a rule is not likely to en- tirely give out. RICHNESS WITH DEPTH. There is no scientific reason why a vein should "grow in richness and size with depth." This is a popular fallac}^ originat- ing from the now less accepted theory that veins were formed by the precipitation of precious metals, by heated rising waters or vapors, and hence that the greater con- centration would take place at greater depths. The "lateral secretion" theory, now by some accepted, ascribes the deposition of ore to solvent waters reaching the vein from ground quite near to it and coming naturally from above and the sides quite as often as it is ejected upward by pressure from below. Plate LX. Pocket and Pinches Resulting from slip- ping_ of uneven Walls of Fissure. i !^ i ! 92 In Idaho Territory, says Mr. A. Williams, "the rule is rather that veins grow less rich and strong with depth, though strong veins may continue metalliferous to a greater depth than mining can ever reach. "The thickness of the earth's crust which we are able to explore is very limited. Increase of heat, as in the deep Comstock mine, and other natural difficulties, limit us to a few thousand feet — 3,000 at most. These deep mines have not, as a rule, proved richer with depth, but to the contrary. Some veins have been worked through alternate zones of richness and barrenness. The Comstock, which has been opened for four miles in length and to a depth of 3,000 feet, shows the ore bodies to be scattered irregularly and the barrenest ground is at the bottom. On the other hand some of the most celebrated mines derived their wealth from rich ores encountered near the si'rface and have proved most disappointing with depth." Atmospheric action for a long period has often reduced the ore to its richest compound, and when the hard material is reached, leanness sets in. This, as we have observed, is commonly the case with gold veins. The richness of the Leadville mines is derived from their decomposed com- pounds. Again, as the surface crust can be so little ex- plored by mining, it is to be remembered that the erosion by glaciers and waters has already removed thousands of feet of the vein, so that we are able to examine only a small fraction of it, while an unknown quantity lies in the depths below. If these veins, then, continue to the supposed great depths below, we are vary far from their starting point, and erosion having removed their upper portions, we cannot find their surface finishing point; in other words, it is not a fresh " ready made " vein we find, but portions of an old vein already extensively mined by the processes of nature. So far as our experience goes in Colorado, after a moder- ate depth is reached below surface action, or below the "water level," a fissure vein may grow richer or poorer, wider or narrower with depth, without any law except local experience in a district. VEINS IN GROUPS. Fissure veins occur in clusters and nearly parallel groups, forming a mining district, and again in that district certain peculiar veins may be grouped together, forming a " belt." Thus Boulder district occupies a certain isolated area, out- 93 side of which few mineral deposits occur for a long distance. We have also in that district several distinct belts carrying; different characteristic ores, such as the telluride belt, marked by rare telluride deposits, the pyritiferous gold- bearing belt, and the argentiferous galena belt. The Central City region is characterized by auriferous pyrites belts. Georgetown district, not far distant, by argentiferous belts, and Idaho Springs, lying between the two, by both gold and silver belts. CHAPTER VIII. RELATION OF VEINS TO ERUPTIVE FORCES. The ultimate cause of the richness in veins of a district or locality is, that local dynamic and eruptive forces were more energetic there than elsewhere, causing great disturbance of the rocks, accompanied b)' fissures, and eruptions of por- phyry. Thus at Leadville, the Mosquito range is violently folded and fractured, eruptive rocks have issued abundantly, and associated with such phenomena we find great lead and silver deposits. Further south the great San Juan district is split up in an extraordinary manner with great fissure veins. The region is an eruptive one, consisting of prodigious flows of eruptive rocks traversed, not unfrequently, by newer eruptive dykes. In the Gunnison district the strata have been overturned, disturbed, folded and faulted in an extraordinary manner by the intrusion of great masses of eruptive rock forming the peaks of the Elk Mountains. The strata everywhere are riddled by dykes or intrusive sheets, and the evidence of heat is apparent in the general metamorphism of the entire region. Mineral veins abound. The same phenomena are repeated more or less in the neighboring region around Aspen, and at Pitkin and Tincup. At Boulder, Central and Georgetown there is a concentra- tion of eruptive dykes locally in each district, and few dykes or eruptive rocks outside of those districts. On the other hand we have no ore deposits in the undisturbed rocks of the plains or the flat basins of our parks, and notably our mining districts are for the most part well into the core of the mountains, where, in the natureof things, folding, crump- i 94 ling, faulting, eruptions and metam<:)rphic heat were more energetic than along the flanks and foothills of the range which have usually pnjved unproductive. The older eruptive rocks such as the quartz, porphyries and diorites of tne Leadville. South Park and Gunnison dis- tricts, are more favorable to the production of ore deposits as a rule, than the more modernly erupted lavas, such as basalt or dolerite which we commonly find occurring in dykes and surface overflows, traversing or capping our Cretaceous and Tertiary cr- phyry. rusty and much decom- posed near the surface where it yielded free gold; with depth this passes into copper and iri)n pyrites. The vein is fri)m an inch to f(jur feet in width ; stringers carrying ore extend into the porphyry, which is highly charged with pyrites which doubtless supplied the \-ein with mineral throusfh the Platk LXI. Gold Vein or Gold Bearing Dyke, showing Oxidized and Unoxidized Portions. agency of surface waters. In Arizona, near Prescott. at the Lion mine we find a green dyke of eruptive diorite penetrating granite. This dyke is traversed by numerous small veins of white quartz which near the decomposed and rusty surface are rich in free gold. At slight depth tlie quartz \-eins become charged with unox- idized iron pyrites sutficiently rich in gold to merit treat- ment by smelting. The surface ore is treated by a simple •' arrastra." and is. of course, free milling. The gold seems to be mostly confined to the quartz veins. FISSURE VEIX.S IX IGNEOUS AND GRANITIC ROi. l-LS. The San Juan district is an exceptional case where im- mense numbers of fissure veins penetrate igneous eruptive sheets. The fissure veins consist of hard gray jaspery quartz, traversing lawi sheets whose united thickness is from 2,000 to 3.000 feet. The veins produce lead, bismuthinite, gray copper and other sih'er-bearing (tres. 96 In Colorado true fissure veins are most characteristic of the Archa-an granitic series. In fact, all the veins in that series are fissure veins. Locally they (Kcur as in the San fuan, cutting through eruptive f(Kks. Outside of these "formations few true fissure veins occur. An exception may be made of the Gunnison and Elk Mountain region where the fissures traverse all the forma- tions from Arcluean granite t(j the top of the Cretaceous coal beds. Nearly all other mineral occurrences, such as those in the limestone regions, come under the class of bedded-veins or blanket-veins, pipe-veins or "pockets" and show none of the characteristics of slipping motion or fis- sure action. Under this latter class the Leadville and As- pen deposits may be grouped. Ore deposits commonly occur at the junction or contact of two dissimilar rocks, as between (luartzite and limestone or limestone and dolomite. Lodesoccur also between the stratification planes of the same class of rock, sandwiched in between two layers of limestone, and sometimes impregnating the layers (jn either side for some distance from the dividing line between the two strata, which is commonly the line of principal ci^ncen- tration of ore, and often descend from tnis concentration line, through the medium of cross joints, to form large pockets in the mass of the limestone. The Aspen and Leadville deposits are of this character. Also when (jre bodies occupy a true fissure, /. ur fissure veins in granite and gneiss often impregnate the walls to a small extent. Mineral deposits favor as a rule the older rocks, such as the Archiean and PaleozcMC series, probably because heat and metamorphic action are commoner in these older rocks which have felt all the throes of the earth from past to present times, than in the more recent ones, and such cir- cumstances, as we have stated, are peculiarly favorable to vein formation and mineral deposition. The bulk of our precious minerals in Colorado comes from the older Archaean and Paleozoic -series of rocks, the ex- ception being the Gunnison region around Crested Butte, Irwin and Ruby, where ore comes from fissure veins in the Mesozoic Cretaceous rocks. The exception is accounted for by the local metamorphism, heat and eruptive phe- nomena of that region. 97 The veins in the San Juan ha\'e also been ascnboH by sninc to the Tertiary Period, owiiij^' to their occurrenct- in certain supposed Tertiary la\'as co ering that district. Besides heat, nietamorphisin, dynamical disturbances .;nd eruptive agencies, other minor circumstances may fa\-or ore deptjsition. Certain rocks, suclias hmestones, mayolTe:. by their tendency to sohibihty and chemical reactions, more fa\orable conditions than others lor mineral solutions to ieposit by " metasomatic " interchange between mineral ard limestone, until the limestone is gradually replaced by ore, much in the same way as the elements of a water-logged trunk of a tree are replaced by silica in the process of fos- silizati(jn. CHANGE OF MINERALS WITH DEPIH. Lodes often change in the character of their PMuerals with depth. n(H only after they have left the zone l* sec- ondary decomposition and surface action, but also far below it. Thus, in the San Juan, some of the mines abound in zinc-blende near the surface, which with depth almost dis- appears, giving place to grav copper and other superior ores. In Cornwall, England, the shallow workings yield copper, and with depth, tin ; and hjcally, many such changes may characterize a particular district but cannot be formu- lated as a rule for other localities. INFLUENCE OF COUNTRY ROCK. In most mining regions, to which Colorado is no excep- tion, a relation has been observed between varieties of '■ country rock " and ore deftosits. Veins in passing from one country rock to another are liable to change in the size or variety of the ore, widening in connection with some rcKks. and pinching or growing narrower in connectirly porous, aiul beinj^ much j< "loam bag." If he discovers prospects f)f gold, he finds his w^ay back to the spots the samples were taken f"'om, so as to continue his up-hill search, and trace the gf)ld to its source or vein. Sometimes there is no indication of a vein, soil and bushes and debris cov^ering its out-crop, but by loaming, the prospector ascertains its position, so as to expose it by a trench not many feet in length. We remember an ingenious way in which a valuable and long sought f(jr vein was at last discovered. Prcjspectors had long found very rich "float" at the base of a hill whose surface was so deeply covered with loose debris that no trace of the vein could be fcnind. A prospector found a small lake on top of this hill, and conceix'ed the idea of cutting a trench from this body of water to the edge of the hill, and by damming up the trench, and then suddenly letting out the water to full force, it cut a deep trench through the loose debris down to bed rock and the vein was discovered. This process is called " boom- ing." The cleavage of quartz is said to be freer, sharper and bet- ter defined, in gold-bearing quartz than in that which is bar- ren. Pj'^rite is a good indication. A soft, fatty clay or gouge often flanks the vein in its gold-bearing portions. The mountain spurs should first receive attention for veins; if the quartz is hard, it stands up, if soft, as it more commonly is, it will leave a streak-like depression. On find- ing such, the prospector should first wash out some of the decaying rock. If only a trace of gold is found in the quartz, there is probably a gold vein in the neighLoihood, and trenches should be dug and exploration systematically fol- lowed up. Gold is generally near one wall of a vein, seldom all through the stone. Quartz gold occurs in "shoots" with barren spaces. Before setting a valuation on a discovery, the facilities for working the mine, such as we have alluded to, should be considered. Placer mines as well as other mines are often supposed to be " worked out." These are sometimes well worth investigating and examining by cross-cuts or other I lO means. S(jmctiines it happens tliat more ^<>\<\ is obtained from " leafier" veins that nad been overlooked, than from the main worked vein. (Jnite C(jmmonly. especially in the lower part of a placer, the pebbles and sand are firmly cemented tof.fether int?old is fcHind in rounded pfrains and in minute crystals, anrl threads deposited by a solution of sulphate of iron .it the moment of the reductif)n of the latter to a sulphide." BABKLT Plate LXVIII. Deep Placer, T.ible Mountain, Cal. — A A, Ancient River Channel, with (iold-hear- ing Gravel ; B B, Sandstones and Shales with Fossil Bones and Silicified Wood. The dead rivers of California are on the west slopes of the Sierra Nevada, from 500 to 7000 feet above sea-level. The largest and richest lead is the " f^ig Rlue Lead" traced 65 miles and even no miles. It is parallel with the main divide of the Sierra Nevada. The live modern rivers run at right angles io it, cutting canyons 1,500 to 3,000 feet deep. The " Blue Lead " runs across these ridges from 200 to 1000 feet below their summit. The lead was disc(jvered by fol- lowing up surface washings. Miners found that the modern streams were richly gold-bearing up to a certain point, in- creasing as this point was neared but ceasing when it was passed. These parts were in the line of the different streajns, and by following up indications, the lead was eventually struck on several sections and tunnelled on. The deposit is 300 feet deep, composed of gravel, boulders, clay, and sand, on strata distinguished by degrees of fineness, by the character of the rocks, and the amount of gold, also by "3 Colors, the prt.'\ailiii>; lolor bc-in^,' a bhic-jj^iay. (»old is Courser near the bottom, anri contains a >j;reater alloy of silver. The silver in the f/oiri in the upper strata, has been eaten out by suiphuiDUs acid resultinj,' troni decomposition of iron pyrites. The whole deposit is like that in e.xisting ri\iis, showiu)^' banks, bars, cfldies, falls, rapids and rillles Tlu-re is nuu li ^okl in the edtiics and but liltfe in the rapids. The space between the boukiers is tilled with sand and con- tains fjold, the bed-rock is slate. Where dead-ri\ers meet, the "wash" is j^enerally rich. Where a lead becomes very narrow, dips fast, and isinchjsed between steep walls, the ^old will be \ery sparingly dis- tributed in holes and behind rid>j^es anfl will be coarse in size. \'ery larjj^e and abundant boulders in j^old-bearinj^ stream beds are often a serious obstacle in jj^ettinjj;^ out the j,^old, from the dilliculty of handling them. More than one placer has been abandoned from this cause alone. HVDRAUMCS. Placer banks are worked on a larjj;e scale by "Giant nozzles " or Hydraulics. Before commencing such work the total depth of the placer deposit should be examined anfl ascertained, and the richness of the strata th;.)Uj.>^hout tested. Shafts should be sunk here and there to bed rock for this purpose, and topographical surveys made tt^ ascer- tain what fall and head of water can be obtained, and what outlet also for the tailings, as the latter would soon choke up the work; the ground sometimes may be too flat to dispose of the tailings by stream-power. The choking of outlets is a fertile source of abandoning placers. Jh'iu/t Mining. — "The beach sands of the Pacific and else- where contain minute scales of gold and s(jmetinies platinum, together with a great deal of magnetic iron ore. Winds, tides, and surf act as natural concentrators or separators, in parting the light and useless material from tlie heavier. Wind drives heavy swells on the beach at high tide to- gether with sandy matter. At ebb ot tide, the surf lashes the beach and carries back light portions of the mass with the undertow, lea\'ing some iron sand, gold and platinum, whose weight enables them to hold their place. At low water, miners go down on the beach, scrape up the iron sand, which is generally left in thin layers, stacking it back from reach of the surf, and subsequently washing out the Kt; 114 gold." In some beaches much of this sand contains titanif- erous iron ore and if attempts are made to use certain pro- cesses to save the finer gold the character of the iron may be a formidable obstacle. EXAMPLE OF COLORADO PLACER GOLD MINES. California gulch, the site of the present Leadville, fur- nished a great amojnt of gold in the early days till the dis- covery of the lead-silver deposits in place. This discovery, also, was due to placer mining. Whilst examining the gravel in the gulch, Mr. Wood, an intelligent prospector, was struck by the appearance of what the miner* railed " heavy rock" some of which he assayed. His specimens yielded 27 percent, lead and 15 ounce's silver to the ton. He put prospectors to work to find the croppings of the ore de- posits, and in June, 1874, the first "carbonates in place" were found on Dome Hill. This was practically the beginning of Leadville. It is said that upwards of 2,000,000 dollars worth of gold was taken out of this gulch in one summer before the mines in place were discovered or opened up. It is noticeable that California gulch alone furnished almost all this placer gold, whilst Iowa and Evans gulches adjoining it on either side, and carved out of the same series of rocks yielded little or nothing. Why should the smaller gulch contain exceptionally rich gravels and its neighbors be barren ? The richest portions of California gulch were found at bends in the course of the gulch. In one place near Oro in the narrow bed of the gulch, a gold-bearing cement was found containing hydrated oxide of iron, below the gravel, yielding an ounce of gold to the ton. The gulch-gold was worth $19 per ounce whilst that froii the mines in place only $15. The Printer Boy porphyry containing actual gold veins in place may have been the source of some of the gold in the gravels, together with the oxide of iron resulting from the decomposition of pyrites in the pyritiferous porphyry as a cen^.enting material. Also the "Weber-grit" sandstones at the head of the gulch have been found to carry small gold veins, and from their abrasion also gold-bearing gravels would have been carried down the gulch. Also of late the rich gold deposits of Breece Hill at the Ibex and Little Johnnie mines have been found. " It is doubtful," says Mr. Emmons, "whether in general, all or even the greater part of the gold contained in placer 1»> gravels is derived from the abrasion of actual gold veins. Traces of gold ma}' be found in a very large proportion of the massive rocks which form the earth's crust, ^old veins nre concentrations of this mineral in sufficient quantity to attract attention and yield a profit. But doubtless there are a vast amount of smaller concentrations which may escape notice. As the rock disintegrates and is worn away by atmospheric agencies, the gold from these smaller de- posits as well as from the larger is set free from its inclosing rock and subjected to the concentrating action of mountain streams. " Placer deposits are the results of nature's vast sluicing processes. To bring them into the condition in which they may be made available by man, requires not only the gold- bearing rock, which her agencies may grind u'^ into sand and gravel, but the sifting power of rapid streams, which may carry down the lighter and coarser material, and a suit- able channel, in which the heavier parti^'les may lodge, as in the ritHes of a sluice box. All mountain gravelt^ all sands of rivers coming from the mountains, contain a cei'tain amount of gold, but it is only under peculiarly favorable conditions that the gold is so concentrated as to render the gravel remunerative. "Among the most favorable of these conditions is a com- paratively narrow channel having a hard and compact bed- rock, and ridges or bends in its course, which by causing a partial arrest in the rapidity of the current shall allow the heavier particles of gold to settle to the bottom, and hold them there when once they have settled. " From this point of view there is a very evident reason why California gulch should have furnisned rich placers, and why the gold which may exist in Iowa and Evans gulches should not j^et have been extracted even though the detrital material which has been carried down the gulch should originally have been equally rich in gold. " California gulch is a valley of erosion, formed entirel)' by the action of running water, and since the glacial period. It has therefore a bottom or bed of hard rock. Its trans- verse section is Y shaped and therefore favorable for the concentration of heavy pailicles at its bottom. When com- paratively full of water, its numerous bends formed eddies in the down flowing currents, and allowed a longer time at these points for the settling of the surface p'lrticles, and as it cuts across many dififerent furmations in it?:, course, its bed must have transverse ridges, which have caught some of ■^ 1 a' ! I 116 the gold and prevented it from being carried farther down the stream. " Evans and Iowa gulches on the other hand are glacier- carved valleys. Their courses are straight, their bottoms broad and comparatively smooth. The glacial moraine ma- terial with which they are largely filled nas not been sub- jected to the siftingor jigging process to which gravel is sub- jected in the bed of a stream. The lower part of their pres- ent beds is cut, not out of rock, but out of the loose gravelly formation of the ' Lake beds.' This later bed, along which the material brought down by post-glacial erosion has been carried, has not a sufficiently hard and permanent bed-rock to allow of Ihe concentration of gold on its surface." ALMA AND FAIRPLAY PLACERS, SOUTH PARK. Along the banks of the Platte river are enormous masses of glacial morainal matter consisting of boulders and sand brought down partly and principally from Mount Lincoln and receiving contributions from side glaciers of the Mos- quito range. This material forms undulating banks on eithei side of the river. This placer "wash," from 50 to 100 feet thick, is worked for gold principally at Alma and Fairpiav. At Alma the heavy bank of "wash " is mined by the giant nozzle. The banks are also cut back into blocks of ground, by water from a flume, which is let out at intervals along the bank above ; at each place it cuts a narrow ravine in the loose debris and at the same time makes the banks easier to be attacked by the water of the giant nozzles which rapidly undermine them. The water and sand from these streams run down into the sluices, whose bottoms are paved with discs of wood, forming "riffles" to catch the gold, whilst the lighter sand is carried onward by the stream. In their "clean up " in the stream bed, they not only wash down to bed-rock, but after hunting with their knives in every crack and crevice of the latter, they dig it up for a foot or two, and further examine 't. The rock is a jointed sandstone. OuicKsilver is thrown into the sluices, to collect the finer gold which is afterwards retorted. Whilst gold is found all through this bank of "wash " from "grass roots " doVv^n to bed-rock, the greatest quantity of gold and largest nuggets are found at " bed-rock " or in its interstices. The source of some of this gold mav be a series of large, but not very productive quartz veinsjn granite, near Mount 117 Lincoln, whence the main glacier originated. It is also probable that a good deal of the gold came, as said before, from the breaking up of the various rocks in which it was disseminated, more especialh' the porphyries and crystalline rocks. In the winter, owing to freezing of the water supply, the work has to be discontinued till the following spring. CI PTER XJ. MINING REGIONS SHOWING EXAMPLES OF ORE DEPOSITS. FISSURE VEINS IN GRANITIC ROCKS. Having described in previous chapters the nature of veins, ore deposits, etc., and how to prospect them, it will be of interest as well as profit to the prospector, to learn something of the mines and mining regions themselves. For this purpose we propose giving a sketch of some of the leading mining regions of Colorado and the West, as in- structive illustrations and examples of what we have writ- ten in previous chapters. As we said in our advice as to the education of a prospector, the best education for him is to go to, and spend as much time as he can in, the mines and mining regions themselves. We will take first the regions characterized by fissure veins. These veins are in the granitic and igneous districts of Colorado. In the granitic ranges, the mining districts of Boulder county, Gilpin and Clear Creek, are the most noted, the principal mining towns being Boulder, J imtown, George- town, Central and Idaho Springs. HOULDER MINES. The geological features of Boulder consist in a series of ridges or hogbacks rising up from the prairie and flanking the granite mountains. These represent Mesozoic strata consisting of sandstones, limestones and shales, containing beds of coal and other economic products, but no precious metal. Volcanic action has occurred in their vicinity as ii8 shown b}-^ a large dyke of basalt at Valmont. These hog- backs, so universally present, flanking the granite mountains, are, in Colorado, destitute of precious ores. Inside of and west of these is the Archa3an granitic front range, C(jnsisting of heavil}^ bedded granite-gneiss, profusely traversed by veins of " pegmatite " or very coarse sparry granite, consist- ing of white feldspar and quartz, with very little mica, and from a few inches to 40 or 50 feet in width ; with these also occur some dykes of eruptive rock, some of it a dark black rock like basalt, called "diabase"; others are lighter col- ored quartz porphj-ries and diorites. In the telluride belt, whilst pegmatite veins are abundant, eruptive rocks are scarce, but west of the telluride belt, which is more or less confined to a special area underlying the Magnolia, Sugar Loaf, Gold Hill and Central districts, enormous masses of eruptive rock are found, but no tellurides. In the non-tellu- ride districts, such as Caribou, Ward and Jimtown, rich silver ores are found associated with galena, gray copper, etc., and gold ores associated with copper and iron pyrites. Thus there are two or three distinct belts in the region, a telluride gold belt, and a silver belt, and a gold pyrites belt. It is noticed that the entire region has been locally disturbed b)^ volcanic forces, and volcanic rocks abound ; outside of this disturbed region there are no mines for a lonfT distance. ihe Boulder mines are celebrated for the occurrence of telluride minerals, some of the richest and rarest ores oc- curring in npture. These ores are confined to a belt occupy- ing the eascern part of the district, and nearer to the hog- back region of the plains than any other important ore deposits in Colorado. West of this belt in the Caribou district the ores are argentiferous galena, with brittle silver. In the Ward dis- tiict pyrites ;il^ound, and where it is decomposed the gold is free. The pyrites though gold-bearing are difiicult of re- duction. The pegmatite veins containing the ore stand at a high angle and are often very wide, but the rich ores, especially the tellurides, arc concentrated in thin streaks and not very con- tinuous bodies. The gangue or vein material is simply an alteration of the adjacent granite, or gneissic country rock, into a more sparry, larger crystalline form, consisting of quartz, feldspar, and %ome mica. This is impregnated with rich mineral, whose source is probably not far to find, the metal elements being microscopically or chemically diffused 119 throuf^h the mineral elements composinji^ the adjacent countn' rock, which is sometimes porphyry, and at others gneiss. This impregnation has taken place either along the contact of an eruptiv^e rock with the country rock granite, or else in a pre-existing vein of pegmatite, or along some fault or jointing plane in the country rock itself which has been favorable to the concentration and precipitation of metallic minerals from their solutions. The direction of the vems is generally between Northeast and Northwest, or East and West ; their dips are steep or vertical. The quartz of the pegmatite gangue, when impregnated with telluride ore, '. s a pale, bluish-gray and rather greasy appearance, streaked here and there with a dull, blackish, greasy stain, upon which sometimes the true telluride min- erals such as sylvanite, can be seen, generally in long thin crystals of a bright tin-like appearance. It is sometimes called graphic tellurium, because the crystals crossing one another assume 'uhe form of Hebrew characters, Syh^anite is a telluride of sliver and gold. There are many varieties of telluride, some rich in silver and others in gold, and some with both combined. When a piece of gangue containing tellurium is roasted, the gold comes out in good sized globules on the surface. Two great mother-veins, called the Maxwell and Hoosier veins, traverse the telluride district for sev^eral miles, easily traceable by their rusty color. One carries pyrites and tellur- ides, the other silver ore and gray copper. Gold Hill dis- trict, in the telluride belt, is traversed by the Hoosier gangue. Several veins cross the Hoosier gangue and are richer in its vicinity ; in some, the ore is a telluride at the surface, but with depth passes down into gold-bearing pyrites. The Ward district outside the telluride belt carries copper and iron pyrites bearing gold. Caribou is silver-bearing, its ores are galena, copper pyrites and zinc-blende occurring in gneiss near a dyke of eruptive diabase. The No-Name vein crosses and faults the Caribou vein. Its ores carry both silver and gold ; the ores are silver glance, brittle silver, gray copper, galena, copper pyrites, with native and ruby silver. The copper pyrites carries more gold than silver. The granitic rocks near Boulder are thrown into a series of parallel folds, one series cut diagonally by another. The telluride veins run along the slopes of these folds. The veins are in cracks and fissures coinciding with this folding, some of the main fissures being filled at once by porphyry dykes, the others more gradually by vein material. The ISO veins occur along', on, and near these dykes, al(jng- lines at the junction of the more massive g^rani'te with the bedded gneiss, along and between stratification planes of schist, and along the joint planes of granite. The veins are due to percolating alkaline waters dissolving metalliferous material and veinstone from the surrounding rocks. It is nijteworthy that alkaline springs still exist in the neighborhocjd, as they do also at the mining district of Idaho Springs. The veins occur where the foldings are abrupt, and the direction of the veins is parallel to the strike of the stratification. As a rule the veins are not of great extent. A single vein can rarely be traced on the surface or beneath it for more th; n 600 feet. Before that distance is reached, the vein spi j oft again into another. Where veins cross at a small angle or where a spur branches off from the main vein, accumulation and enrich- ment of ore takes place. There are two courses of \-eins, one East and West, the other Northeast by Southwest ; the former S3'stem appears to be the older as the latter faults it. The ore occurs in chimneys or pockets, with a good deal of barren ground between. Small veins run parallel with each other for some dis- tance, the interval filled with granite or pegmatite. Some- times a vein pinches out entirr^ly (contrarj' to the general habit of true large fissure veins occupying great fault fissures). The ore streak is from i to 20 inches wide con- taining more of this blue, greasy, fine grained "horn quartz" than the country rock. Some of the veins interlace iike arteries in a human body. Minui^ particles of pyrites (marcasite) often produce the dark stains we have noted on the telluride quartz. By moistening the stone, the telluride minerals and pyrite appear distinctly. A TYPICAL BOULDER COUNTY MINE. A good typical and very instructive example of a contact fissure, gold-bearing vein is that of the Golden Age at Jim- town, north of Boulder. "At Jimtown a quartz-diorite dyke occurs, of light color containing much hornblende and titanic iron, running nearly through the street of the village. The cliffs at Jimtown, over 500 feet high, are of quartz porphyry, of white color, consisting mainly of large crystals of quartz and feldspar, set in a fine grained crystalline ground mass or paste. 121 I (;()1.I)EN AOK, AND SKNTIXEL VEINS. From the town, the road winds up a steep mountain com- pcsed of coarse gray granite, with occasional belts (jf gneiss. Here are located the Golden Age and Sentinel mines. The Golden Age covers the outcrop of a (juartz-porphyry dyke cutting through the granite. This dyke vanes in width, from a few Teet to about fifty. The outcrop of the main ore chute of the Golden Age extends along the "con- tact " on the lower side of the porphyrv dyke. At a depth of IOC feet the main shaft discloses a split in the vein. The hanging wall of the ^'ein continues into the dyke, but with jiorphyrj' hanging and footwalls, until a depth of 330 feet, where it enters the upper contact between the porphyry and granite. The dyke has been much acted upon and decomposed by vein forming agencies in the upper work- ings, but in the lower it is less decomposed and shows con- siderable pyrites. The Golden Age veins are well defined, presenting a banded or ribbon structure. They are inclosed in distinct walls with gouge or selvages, which at times show slickensides. The seams and feeders that have' enriched both veins come in from the porphyry dyke. The ore from the Golden Age contains rich and magnifi- cent specimens of free gold It is a free milling ore. When rich, the gangue is a hard, flinty, vitreous white quartz. The gold is seldom accompanied by pyrites. It is generally imbedded in the white quartz as bright yellow gold, in size, from coarse grains to nuggets several ounces in weight; after it reaches the lower contact between the porphyry and granite and enters the granite, there is an increase in the baser metals, such as zinc-blende, galena and pyrites, but the ore still retains its value in free gold. Returning to the surface, ■'he Sentinel location covers the apex of a vein, which there appears enclosed in a belt of schistose or gneissic rock. This vein dips South at an angle of 70° and passes through the Golden Age vein on its course. The Sentinel vein ore is entirely distinct from that of the Golden Age. It is the characteristic bluish horn quartz of the tellurium veins of Boulder County, with characteristic chalcedony quartz crystals and finely disseminated pyrites. The value is in metallic gold and such tellurium ores as petzite and sylvanite. Whilst most of the gold was deposited as native gold, a portion has evidently been rendered free by partial decomposition of the tellurides. This ore is very 122 rich. The richest ore usually occurs in two narrcnv seams or streaks from a foot to ten feet apart, the intervening- space being more or less mineralized country rock. It is richest when in the schistose rock, and poorest when it passes through the porphyry dyke. The crossing of the Sentinel vein through that of the Golden Age is very clearly marked ; it very slightly faults the Golden Age vein. The gold mines of Boulder County belong to two distinct periods of vein formation ; to one beh^ng the non-telluride ores, and to the other those producing tellurium. The tellurium veins appear to be the later of the two. The ores of the Sentinel tellurium vein are lower grade where the vein passes through the porphyry dyke. This is due to the Golden Age vein being formed first, and drain- ing the dyke of its disseminated mineral values. The Sentinel received its mineral from the schistose or gneissic rocks, and is consequently richer where enclosed in those rocks than when in the dvke. Vein Plate LXIX. Section of Golden Age Vein, Jimtown, Boulder Co., Colo. Prospectors look for richer or larger bodies of ore when veins unite or cross each other. In the Golden Age the two veins unite about loo feet below the surface. There are similar veins of the same age, and large and rich ore bodies are found at their junction. On the other hand, the Sentinel vein of later age, passing through the earlier Golden Age vein, produced no enrichment of the ore bodies. 1^3 To form such ore bodies, the veins should be of contempo- raneous origin." The ore deposits of (Jilnin and Clear Creek Counties are \'ery similar to those of IJoulder, only they do not produce tellurium ores. The country rock is the same granite-gneiss, penetrated here and there by porphyry dykes. The peg- matitic veins are either in the gnefss or between the dykes and the granite. In some cases the porphyry dyke Cfjnstitutes a vein in itself, such as the Minnie, which is a felsite porphyry, and the Cyclops, a quartz porphyry, In (iilpin county, around Central City, the ores are a mixture of copper nyrite and iron pyrite with a very little galena and zinc-blende. All are gold-bearing. The richer ore occurs in streaks not over a foot wide, in a compact, fine grained mass of pyrite. Copper pyrite is richer than iron pyrite. The rest of the vein, often manv feet wide, carries pyrite irregularly disseminated through decomposed country rock. The bulk of these ores are difficult to treat, and are milled, the loss being 40 per cent, higher in the unoxidized ores than in the oxidized. The veins follow the cleavage planes of the gneiss, cutting the stratification planes at right angles with a vertical din. The porphyry dykes are older than the veins, as the cleavage planes intersect both the porphyry and gneiss alike. For an interval of 20 miles between these mining districts and the plains, there are no ore deposits of any importance known. In Clear Treek County the ores are mainly silver-bearing ; the silver is derived mainly from galena and gray copper. Dykes of obsidian occur in one of the mines parallel with the vein, which is itself a porphyry dyke. The richest min- eral is close to the obsidian dyke. FISSURE VEIN.S IN TRUE IGNEOUS ROCKS. Whilst most of our fis?:ure veins and ore deposits gener- ally are more or less associated with the presence of igneous rocks, there are some which are essentially in igneous eruptive rocks alone. The most remarkable of these are the fissure veins of the San Juan region in southwestern Colorado. This region consists of an enormous plateau of lavas of great thickness resting upon and originally overflowing a a low mountain range or plateau of granitic and upturned sedimentary rocks, the latter representing most of the geologic periods from Cambrian to Tertiary. The hickness vm '<^/.y'. (/:■ We kS^ ^>^-' t-^1'fht of 14.000 feet above tiie sea. The lava sheets are also tra\'ersed to a depth of 1,500 feet more or less, by an extraordinary number of f^^reat quartz-fissure veins. These veins appear to till shrinkaf>^e cracks resulting from the con- traction on co(jling of the lava sheets, strictly speaking they are rather "gash \'eins" on a larger scale than " true fissure \'eins." fc^r they are mostly Itmtted to the thickness of the laTa o^rrjliru's and cease when they reach the under- 1\ ing granite. There appear to have been two principal eruptions; the first, dur- ing the early part of the Tertiary, covered the higher region of the San Juan mountains to a depth of 1,500 feet with an overflow of brecciated andesitic lava, which on cooling developed fissures of contraction traversing the lava mass in all directions; these were subsequently and slowly filled with a hard bluish quartz contain- ing more or less ore. Following the first grand over- flow were others of less magni- tude, consisting of non-brecciated andesites and rhyolites. This sec- ond dynamic movement produced locally, fissures extending below the horizon of breccia into the stratified rr,cks, These, however, 12 5 are selfloiii productive below the eruptive zone. There are also metal deposits in connection with still older eru|)tions ot andesite and diorite. such as Mineral Kariu. Calliope, etc. RED MOUNTAIN. In the Red Mountain district the ore deposits form a ])eculiar group. They occupy a series of more or less 126 C()n?iocted inojijular chambfrs, trciulin^flowiiwaifl, pmhahly channels of ancient hoi mineral spring's, 'I'lie niinerah/inif water completely silicilied the surrounding^ erupti\e rocK for some (hstance away from tlu' ore chambers. So the ore bodies are distributed throuj,'ii a hu^rf jiivjrular column of quartz extondinjj^ to an undetermined depth. Larja^e masses of brilliantly colored ..laterial are conspicu- ous in this region. 'I'hey have been acted upon by mineral waters circuhitiiifj^ throujj^h their crannies and lissures, Ore bodies are occasionally found in these and such mini's are locally known as cave mines. The ores of the San juan are mostly arj^entiferous f^ray copper, copper pyrites and jj^alena associated with zinc- blende and iron jtyrites in usuallya hard horn-(piartz matrix. Some of the ore locally contains a hif>^h per centaj^e of bis- muth; others produce pyrar^yrite ann polybasite, rich silver minerals; others carrv considerable ^o\(\, such as the recently discovered gold belt at Ouray. This belt occurs in Dakotah Cretaceous sandstone, which has been altered into a quartzite by the intrusion of dykes and sheets of erujitixe diorite. One of these sheets spreads out in the (piartzite. The ore occurs at the top of the quartzite, at its junction with a bed of shale. The fj^old, which is free and enclosed in brown oxide of iron, doubtless orig-inated from the |ior- phyry, and entered the joints and beddinj^ planes of the quartzite, where they were opened by faulting. Aboxe the shale the ore does not penetrate, the shale acting as an impervious resistance to uprising solutions. Ore bodies also occur in the Jurassic limestones below the ([uartzite, especially where they are penetrated by eruptive rocks. In the eastern portion of the San Juan region some important gold deposits occur near Del Norte in the Little Annie or Bovv'en Mine, which appear to be a decomposed dyke of eruptive rock, containing free gold in brown iron, in the upper portion,, and with depth iron pyrites also gold- bearing. CREKDE. At the newly discovered camp of Creede, not very far from Del N(jrte, the fissure veins are very similar in char- acter to those elsewhere in San Juan; they are quartz fissure veins traversing andesitic breccia and other volcanic rocks. The gangue matter in the?" veins is exceedingly rich in silver-bearing ore, so much so that the amethystine quartz composing the gangue or veinstone is quite in a ■■■t 1: 127 minority to the ore, and the vein may be said to be nearly a mass ot ore from wall to wall. The thick lavas of Crced*^ rest donbtless with deptli npon ("arhoMiterous limestone ot else on bare granite ; the fornu-r is found outcroppinj^ at some distance from Creede, from beneath the lava overtlow, and bi'in^ penetratinl by intrusive rruptive rocks shows sijj^ns here and there of prorhictive ore deposits similar prob- ably to those at Leadville. Creede is an encoura^inj^ example to a prospector, that all productive veins in Colo- rado lia\'e not been discovered yet. e\'en in districts that ha\e been pretty well tramped o\'er. Creede had doubtless ')ften been more or less walked over bv prospectors for vcars before the jj^reat discovery was made, and in a ye'ar's time we may hear of several more similar discoveries in the jj^reat San Juan. ROSITA AND SILVKR CI.II F. The next important and peculiar ijj^neous district carryinjj^ lissure \'eins is that of Rosita and Silver ClitT in the Wet Moup.tain Valley near the edge of the prairie country in southeastern Colorado. Here a local eruption of consider- able power and magnitude and of comparatively recent date has occurred. These eruptions, consisting of andesitic, rhvolitic and trachytic material have built up cones and rounded b.ills largely of fragmental material such as consoli- dated tuffs. ashe«, and breccia, all of which, as at Cripple Creek, rest on granitic basement rock. From the fragmen- tary character of th(i rocks it is evident that most of the t^ruptions were explosive, alternating, however, with quieter flows; in some cases the dykes can be seen, where some of the lava came, at others the "necks" or throats of the volcanoes themselves filled up with volcanic boulders; of such is the celebrated Bassick Mine. The mine is in the throat of ai^ old crater of andesite, tilled with boulders of granite and andesite bedded in gravel and sand. The ore of the Bassick appears as concentric /ones or shells around these boulders, as a replacement of the gravelly matrix. The entire mass has been permeated by heated waters which have decomposed the rocky fragments, depositing opaline quartz and kaolin in abundance. The concentric shells around the boulders carry alter- nately several minerals, such as galena, antimony, zinc-blende, copper and iron pyrites, all more or less gold-bearing. The ore deposition in this region seems to have taken place at the close of the eruptive period, when tfic eruptions were It 128 dying- out into hot sprinj^s, fumaroles, etc., and producing^ great decomposition ot the lava rocks. The district was not thought much of, until Mr. Bassick made his discovery in the unpromising looking throat of the old volcano, con- taining a formation quite anomalous, and which the regular prospector, "ccustomed to true, orthodox fissure veins, would have passed by as very unlikely. So it may happen to future prospectors, that some very unlikely formations may turn out great riches ; hence it is well to keep a sharp lookout for everything examinable. A STUDY OF MODERN LIVING VOLCANOES TO UNDERSTAND THE CRIPPLE CREEK VOLCANO. Bv far the most tvpical, instructive and important gold camp in Colorado and the West is that of Cripple Creek. To 'S^.'^iiiMM'' Plate LXXII. Stromboli Volcano. understand the geology of the Cripple Creek region and gold-bearing volcanic regions and rocks and their relations to the ore-deposits, a knowledge of the phenomena attending modern volcanic eruptions is necessary. Let us take that of the living volcano of Stromboli, described by Professor J udd, as throwing some light on the phenomena that may have occurred many thousands of years ago in the now extinct volcano of the Cripple Creek district. From a point on the sides of the mountain of Stromboli, masses of vapor issue and unite to form a cloud over the mountain. This cloud is made up of globular masses, each of which is the product of a distinct outburst of the volcanic forces. At night a glow of red light appears on the cloud, increasing gradually in intensity, and as gradually fading away. 129 After an interval this is repeated and continues till the- light of dawn causes it to be no longer visible. When we land on the island we find it built up of the "ejecta" from the volcano like a gigantic iron furnace with its heaps of cinders and masses of slag. The irregular shape and surface of the island is due to erosion removing the loose materials at some points, and leaving the hard slaggy masses standing up prominently as dykes and hard portions of lava flows, as. Pisgah, Rhyolite Mt. and others at Cripple Creek do, above the eroded and more fragmentary tuffs and breccias. This great heap of cinders and slags rises 6,000 feet above the sea bottom with a base four miles in diameter; 2,000 feet above sea level is a circular depression, the crater of the active volcano. Looking down into the crater, an outburst takes place. Before the outburst, many light curling wreaths of vapor ascend from fissures on the sides and bottom of the crater. . Possibly this is the origin of some of the dyke-filled fissures- of Cripple Creek. Suddenly a sound is heard like a locomo- tive blowing off its steam. A great volume of watery vapor is thrown up into the atmosphere, and with it a number of dark fragments are hurled 500 feet above the crater, some fall- ing on the mountain, others back into the crater with a loud rattling noise. Those rolling down the mountain are still hot and s em i-molten. This is a clue to the origin of the fragmentary materials composing the tuffs andl breccias at Cripple Creek. The black slaggy bottom of the crater is, as we nave said, traversed by many fissures emit- ting jets of vapor. Some of these are quite large and vary in size and number and position at different periods. From some, only steam is emitted in loud snorting puffs. In others molten material is seen welling up and flowing out— Plate LXXIII. Map of Island of Stromboli. I30 side the crater. Such fissures when all eruption has ceased would be found, as at Cripple Creek, sealed up with solid Plate LXXIV. Stromboli Crater. lava with a lava flow on their tops. From this liquid mass, steam escapes in considerable quantities. Within the walls of the fissures, a viscid semi-liquid 'av? heaves up and down and churns around till at last a gig. itic bubble or blister is formed which bursts violently and a great rush of steam takes place carrying fragments of the scum-like surface Ol the liquid high into the air. At night the fissures glow with ruddy light. The liquid matter is white hot and the scum on it a dull red. Every time a bubble bursts a fresh glowing is the ver.ection of this upon the clouds of steam surface is exposed. It above the mountain that causes the fitful glows of light we mentioned. The phenomena show there are cracks communicat- ing with the earth's interior highly heated matter be- neath the surface, together with great quantities of impris- oned water, wliich escaping as steam give rise to all the active phenomena. Pl.ATK LXXV. Dykes Cutting Beds of Scoria and Tuff in the Wall of a Crater. 131 What is pv)pularly supposed to be flame in an eruption is the reflection on the cloud of steam and dust, from g^lowing- masses in the mouth of the crater. Sulphur is not, as commonly supposed, erupted from a volcano, but is formed by the union of sulphurous acid and sulphureted hj'drogen issuing from vulcanic vents. A volcano is a steam vent, like a geyser, which may be called a water volcano. ■ ORIGIN OF FISSURES. Some light is thrown on the possible origin of som-e of the Cripple Creek dykes and fissures by the eruption of Vesuvius in 1872. The bottom of the crater was entirely broken up and the sides of the mountain rent by fissures in all directions. So numerous were these fissures that liquid matter appeared to be oozing from every part of its surface and the mountain to be "sweating lire." One fissure was enormous, extending from the summit to far beyond the base of the cone. This, filled with a dyke of hn a, is visible to-day. From both crater and fissures enormous volumes of steam rushed out with a prodigious roar. This roaring was from explosion of bubbles one after another, and the vapor cloud above Vesuvius, as at Stromboli, was made up of globular masses of steam ejected at successive explosions. Each explosion carried upward quantities of fragments which fell back on the mountain. All along the course of the stream of lava, volumes of steam were thrown off. ORIGIN OF TUFFS. The discharge of such large quantities of steam causes the atmosphere to be saturated with watery vapor, which, condensing, falls in excessive rain storms, producing mud streams formed by rain water sweeping along the loose vol- canic dust and debris. In some such way, doubtless, the Cripple Creek tuflfs and breccias were formed. GASES AND MATERIALS EJECTED FROM VOLCANOES, The most abundant of the substances ejected from vol- canoes is steam, and wiih it many volatile materials, such as hydrochloric acid and carbonic acid, also hydrogen, nitro- gen and ammonia, and at Cripple Creek fluorine gas. These different gases at Cripple Creek had much to do with the formation of ore deposits. Volatile metals, such as 132 II •arsenic, antimoii)' and cinnabar are erupted ; these sub- stances, issuing from volcanic vents at high temperature, react upon one another forming new compounds, such as •sulphur. Hydrochloric acid unites with the iron iri the rocks to form yellow ferric chloride, common at Cripple ! heated matter at no j^ieat deptfw is indicated by outbnists of ^^uses and vapor, lorination of jj[eysers, mud volcanoes and hot sprinjj^s. As tlie underlying rocks cool down, the issuinjr jets <»! jj^as and \apor lose their liijjfh temperature, diminisli in (piantity, ^^eysers and inurt volcanoes become extinct, IkH springs disappear, and all is- (piiet. It was in the latter or hot sprinjj; staj^e.that the ores were at Cripple Creek leached from the volcanic rocks, probably frcjin f^reat depths as well possibly as from the sides, and concentrated and deposited in the fissures, shattered zones,, and decomposed rocKs. The last staj^e is as we find thinj^s. tenerally in the moun- tains. We may assun'C that preludinj,^ the eruption the area was- troubled by eartlupiakes. Various kinds of acid and hot sprinj^s appeared above the surface, indicating the tissuring of the ground that followed. At the bottom of ibese fractures, which may have beeni numerous, molten rock appeared, giving otT imprisoned vapor from bursting blisters of lava. These shoots (jf steam; formed into a cloud overshadowing the area, and carried upwards quantities of scoria and fragments, which fell back around the orifices, forming ;» crater cone, or craters. These fragments being repeated!- s) )t up, and falling back into- the crater were comminuted into tine dust, and fell, together with larger angular fragments, ovcv the surface. The atmosphere charged w/h condensing stenmgave rise- to heavy rain falls. The w..tcr descending the ravines,, caught up the volcanic dust and fragments, forming mud- flows, the materia! rapidly setting into the rocks we call tufa's and breccias. As tlie first eruption at Cripple Creek was of andesite, these are called andesitic tuffs and breccias, and constitute the principal mineralized rock of the mining area. These tutTs are sometimes stratified by the materials be- ing sorted in the air by the water. After this lirst eruption ceased, there may have been a I I H2 rest for a time, the lavas may have cooled and ccnisolidated, and the region been covered by xarious acid and hot springs, issuing from fissures caused by tiie late eruption. Then the district was a second time disturbed, this time by an eruption of phonolite, ascending thnjugh numerous rents and fissures, not only in the overlying andesite, but also in the granitic region outside of the first volcanic "focus," probably finding the old seat of action too much choked by eruptive matter. This second eruption added many new fissures to the al- ready shattered rocks, and gave many opportunities for the deposition of metallic and \'ein material deposited through the medium of -^aseous and hot spring and solfataric actioi' which followeci upon the cessation of the phonolite erup- tion. After the eruptions at Cripple Creek ceased the volcanic forces seem to have transferred their field of action to the area west oi Cripple Creek in the Four-mile district. The rest is the history of to-dav. CRIPPLK CRKEK AS A l'ROSPl<:C lINd FIKLD. A visitor standing on top of one of the hills like Mt. Pisgah, overlooking Cripple Creek, and glancing at the various mines and multitudinous prospect holes speckling the hills, is struck with the compactness of the mining dis- trict within the limited area of 18 square miles. In this small area all the principal mines are located, and one can ride arcjund the ent'.e camp in an htnir (jr two. Outside of this area, there are as yet no mines of importance, though prospect holes may be found for a circuit of many miles. i I ANDKSITIC AND GRANITE AREAS. He will observe that the principal mines are located on the round smooth hills, on their tops, slopes and on the gulches, where the vegetation is mostly grass and quaking aspen. These too are within a sort o'f natural rampart of more rugged hills wooded with pine. In these outlying hills, only a few scattered prospects are visible. The reason for this is to be found in the geology of the region, and the dififerences between the areas occupied l)y andesitic breccia and granite. The rounded grassy aspen-covered hills re- presenting the andesitic brecria carry most of the ore bodies, and the principal mines are restricted to them. The 143 more ruf?f?ed hills, covered with tir trees, represent the jjranite area, and in them for the most part are few mines (jf importance, though many hkely prospects are opened upon dykes of phonoMte, which, so far as known, does nc as a rule seem to be so productive a rock as the andesite. There are intermediate areas, such as that of Battle Mt., characterized by the presence of both andesitic breccia,^ phonolite dykes, and granite, in which are some of the richest mines of the district, such as the Independence, Portland, Annie Lee and others. It will appear how important and useful a ge(jIogica{ survey is oi such a region, a fact not always recognized by practical miners. If the ore bodies are mainly associated with the particular rock called andesitic breccia, it is well for them to be able to recognize that rock, and ascertain the limits of its area. SIGNS THAT LEAD TO PROSPF.CTINO. The next thing that strikes the observer, is the prodig- ious amount of prospecting holes and prospecting trenches, the latter being particularly common. lie may ask, what was there in the general appearance and character of this district that led the " eagle eyed " prospector to suspect the existence of ore bodies in it, or that it was "a kinder likely locjking place".'' Again, how is it that it was so long overlooked by the " eagle eyed," especially when so easily accessible ? On general principles, in past years, miners in Colorado, after the Leadville and Aspen excitement, were more on the lookout for silver than gold ; they locjked therefore for rocks like those of Leadville, with contacts between por- phyry and limestone, and e\'ery limestone ledge in the country was ransacked. Silver was rarely found in xolcanic lava rocks, except perhaps in the great San juan region, and miners thcmght as little about prospecting unpromising looking hills of lava, as they would the Ixisaltic caps of the table mountains on the plains. Again, gold leads do not show their ore on the surface like some silver-lead \-eins. There is nothing perhaps but a little seam of rust that might occur almost anywhere, and in any kind of rock. Hence lava districts of somewhat recent origin, were oxer- looked, rather than looked over. The discovery of the gold-bearing properties oi the Cripple Creek lavas, together with the increased thirst for gold, turned the tables, and 1l t 1 144 mow iTiroughout Colorado, every lava formation is being rprogpected with as much zeal and mdiscriniinateness, as \were ihe limestones in the Leadville days. The prospector maw needs to know volcanic lavas at sight, to distinguish '.varieties, and to know all he possibly can about their • origin, varieties and mode of occurrence. Hence the im- iportance we gave to the subject in the preceeding remarks »on volcanoes. A prospector nis we s 149 have mentionefl. Outside of this area his course may be a little different, as then he is in the granite district, and looks out for the appearance of dykes of phonolite, rarely more than a few feet, though sometimes many yards, in width, and easily distinguished from the red granite by their light gray or white C(jl(jr. These dykes do not often appear out- cropping in the granite cliffs, but are more commonly t(; be found buried beneath the debris and grass oi the slopes. On these he may find n(; indication and trust to haphazard trenching; or a few stray pieces may lead him to the spcjt. The more rusty, oxidized and decomposed the phonolite, the more likely it is to carry gold ; at times he may find ore Platk LXXXII. ection Mooss Mine Veil), Raven Hill. i. Country Rock Breccia. ?. Yellow Jasner, with Cavities of _ (Quartz Crystals. 3. Blue Grey Jasper, with Seams of 'juartz and Iron containing Gold. and iVee gold in the dyke itself, but more often at its con- tact, on (jne or both sides, with the granite. There he is likely to find a crevice filled with clay or iron-oxide, carry- ing seams and cavities lined with quartz crystals or stains (jf purple fluorspar, S(jmetimes he may find the coarse granite, as in the case of the Independence mine have something more like defined veins and defined walls. In some cases surface signs have been poor, and with depth have done well ; the exact opposite has often been the case. Some mines have been good from bottom to top, but we have to be careful here, as in most gold camps, of the old fallacy of " richness with depth." There is little more criterion for this than in other camps, and many a once famous mine is looking vainly with depth for its lost bonanza, though in other respects doing fairly well. As regards the granite itself, we have heard of few (ordi- nary quartz fissure veins unaccompanied by lava intrusions proving productive. The fine grained, red, eruptive granite on Barnard Creek, north of Cripple Creek, has shown a promising ore body in a lava dyke in the granite, which, singularly enough, i)ro- duces a fine grained galena, rich in gold. Galena is quite a rare ore in Cripple Creek. Green carbonate of copper stains appear at times in the schists and gneisses, but none so far productive. The railroad from Canyon City to Cripple Creek did s(jme good prospecting work in the granite area, its cuttings exposing quite a number of phjffi^i*!;Q^^^~i:^5^!^^^^^^ Di-ah flolofnitio y^V^^>?*^^S^^5S^^^^^?^ Cnmhrtttn Platf. LXXXIII. Section of Lcadville Cliff. and cliffs of the range and resting on the granite, is as fol- lows, beginning with the lowest : Feet tliick. Cambrian quartzite aoo Silurian drab limestone (dolomite) zoo Lower Carboniferous blue limestone aoo Middle Carboniferous sandstones and (|uartzitc (Weber grits). .2,000 Upper Carboniferous limestones, reddish sandstones 1,000 Total 3,600 to 4,000 These formations have been traversed by eruptive quartz- porphyry and porphyrite dykes and intrusive sheets. The dykes occur principally in the Archa?an, but the intrusixe sheets are many and are spread out between the quartzites and limestones of the Cambrian, Silurian and Carboniferous. ■^SCRS? 153 The connection bctwc>'n the eruptive masses and deposition of ore is very marked. The ore bodies are a concentration of the metallic minerals oriji[inalIy Hisseminated throufj^li the mass of these eruptive porphyries and deposited alonjj; their plane of contact with the sedimentary beds, and by metaso- ni.itic substitution extending more of less into the mass of the latter. On mountains Lincoln and Bross, in the principal mines, the ores are mainly argentifennis, yielding galena and its products of decomposition, vi/., carbonate of lead (cerussite) and sulphate of lead (anglesite) with chloride of silver. Barite (heavy spar) is a common gangue (jr vein- stone especially in the richest parts of tlie mine. Iron pyrites ciecomposed and passing into a hydrated o.xide of iron, together with a black o.xide of manganese, give to the ore its rusty and black color. The deposits occur in irregular bodies or pockets often of great size, in the blue limestone, near its upper surfa ,e, but not always easy to find or follow. This limestone was originally covered by a sheet of (piartz-porphyry which has been locally removed from the ore deposits, but e.xists in the peak. This porphyrv, generally recognized by its large feldspar crystals is calleH Mt. Lincoln porphyry and is quite common and characteristic of Western Colorado. In the Dolly Varden mine the ore occurs in the limestone at con- tact with a 7'ertiial dyke of white (juartz-porp/iyry. In the Kanny Barrett mine, on Loveland Hill, rich deposits of galena and anglesite occur in a vertical tissure (probably a gash vein) crossing the hill from side to side and travers- ing the Paleozoic strata at right angles to their dip, but probably not entering into the underlving granite. This mine was discovered by nt^ticing little pfeces of iron f(jllow- ing a general line across the hill. In Buckskin Gulch the Phillips mine is an immense mass of gold-bearing iron pyrites, deposited, in beds of Cambrian quartzite near a dyke of quartz-porphyry. This mine was dis- covered by its rusty outcrop being exposed along the edge of the stream. At first this crust of iron o.xide was hjose enough to be panned for gold with good success by the old timers, and afterward milled. But when the hard pyrite set in, the ore was found to be too low grade to pay for roasting and smelting, and for many years lay idle. The Criterion in the cliff above this consists of Iari;^e caves in Cambrian (piart- zite, still partly occupied by o. idized gold-bearing iron ore, and galena-bearing silver c/ose to a porphyrite dyke. m '54 The Loiuloti mine in Mi)sr|uit<) «:ulcli is peculiar and instructive as beinjj^ involved in the fj^reat London fault. There are two strong; \eins or de|)osits ol [))rites carryin^^ both j^old and silver, the ^anj^ue ot one is (juart/. the other calcite. They occur in the limestone in connection with an j'nirusive bed of u kite porphyry. These deposits stand in a vertical position, the beds containinjj;- them havinji^ been turned up abvuptl/ against the great London fault, by whose movement the Archajan granite rocks forming the eastern _ -i.:.4-JW-uM i w wisgiBaiB HiaL_j '55 half of Lotuloii Mt. .ire hroujrht up into juxtaposition witli the Silurian aiul (arhoiiik'rous hrrls at its western point. (ioinj.f soulii alon^' the .Mos(|Mito ranj^e the intrusive j'Oip/iyn'ts (iiniinish in cxtvut ivtt/ li'it/i t/triii iiiso t/i>- niiiitrtil iicposits. The Sacramento mine is a j^joorl example of a "pocket"' mine. Rich hoflies of j^^alcna and rich rjccompost'd ores have been found at uncertain intervals in a series of p)ckets or cavities. Some of these poi'kets or cavities an- empty, antl lined with mod'.:rn stalact.lcs, others contain louse landonHill xt Grantt* Platk LXXXV. The London Mine Fiult. sand, with pebbles of rich ore, others are quite full of rich ore deposits. These deposits are difficult to follow with any decree of certainty, and much of the profits made in the rich pockets has been used up in blindly "popherin^" after other pockets. From some of these chambers open fissures or jt)int planes ascend \.o the surface. The limestone was originally capped by a porphyry wh.ich has since been eroded off. 7 his porphyry doubtless supplied the ore. LKADVILI.K DISTRICT. The western boundary of this district is the Sawatc'i ran»;e of Archxan granite. The slope of the Mosquito rantj ■ n t!r 156 cast and the hills on the north, forming the water shed be- tween the Grand and Arkansas Rivers, have a basis of Archx'an granite and gneiss more or less covered bv patches and remnants of the Paleozoic formations, /. e., Cambrian, Silurian and Carboniferous, which have escaped erosion. Their lower position relative to corresponding beds on the eastern or South Park side of the Mosquito range is due in part to faulting, and in part to folding of the beds. Within these Paleozoic f^ormations, these beds of quartzite and limestone, ///<7v is an enormous dc^'clopment of erupth'e rocks, principally quartz-porphyries partially occurring as dykes but generally as immense intrusive sheets following the bedding plane of the sedimentary rocks. Glaciers have been at work also in this neighborho doubtless received fresh crumples in this movement. A minor force also acted north and south, producing gentle lateial folds along the foothills at right angles to the trend of the range. These intjvements were not paroxysmal II ^lllu^^t^^>uc^ aiiu anai^^o vwiii| /v/ui lie neii?hbi)rho()d. which are le^s susceptible to percolatinjr - ~ • ■ formations in America arc the prin- w ater. The Paleozoic ripal repositories for lead and silver ores, not by reason ol their j^^eological age, so much as by their containinfi: such a [uantity of soluble limestones and being physically as wel »59 or siiflrleii and x'iolciit, but [n'otnictcd for an cnornious lapse of time, and apjicar to be continued in diniinisbed force up to the present day. J^li ro Tr-i us Car SUu C'reKctceni t, itJufct 'I r I c/J ojf oiciScct- Crvi'^it r an .•> — . iMfa /'ri'txa ■ Cay ton iftrau ^SIxufettcH Myvfiaaanys^omU ^Si!=^:- o- litc rteof \.'. /. /•/,•(!/ Sntii'H, x/ii>;.'iii,i^ I'tt/ro'^i'.U a ml Mcsozoic Strata, i''ith inn us ions of eruptive KocK\ Iviiti; hinealh Mouiiiiiiii etrvation at I'iose o/' ( ret a \- Crttaceous --^ 3 t/ixrci Trices -, t~ Carbont/67x>tia , GrctntC*.. y {/ I \^^j^iti^Tia*: ^ ) \,^M^»oxoia^ /mS*j5-- /r •>,.■>.., , , , >Af.O'3Vuifr> /i^trliyf Ct'OKl .Vo. a. /,; yes;i.'{ ,./(/,, j^i.-.tt IVt ( 'et.ueous ii/>/i/t cXu^a^c'^i /iuriff Xfciifu r.'o fill ngrr .\r. 3. A7fr,if:' Seition 0/ Lra,Hii/e Distri, t, Mos./uilo A'amr aii.i South l'a> -;■ as it is I'l.ATI. I.XXXVl. Sections to IlliiNtnitc the ('.railti.-il CKoL.nii •«! I tcvclopmeiu <>i ilw I..-, neij^hborhood, wliich are less susceptible to percolating,' water. The Paleo/oic formations in America are the prin- cipal repositories for lead and silver ores, not bv reason of their ^eolopical aj,>^e. so much as by their containinp^ such a quantity of soluble limestones and being physically as well Diis lapse force up /Sta Carton i/rrtji4a_ \ tTn rctTricta Ca rb o n lye, r-ou»i\ Cffnrx t'Jtc Fteof CSolorciolv Fi~ont I^anjyo latarxdt IS of ffupiive RiHk\ lyiiiK h> neatlt thi' Mesozoic Sea, bitween Sawatch and Front Kan,i,t /s/aiuh prior to the great tiiii in cli-'ittion iit i lost- <\/' ( ri'/in tons. CretaccoLca >7icrct7~i~ia.a C^otrtZH J^'ctf/c Jja-sin. Color'acla /■'ron.t flancyu t//oli/t '' '/,, f, I III' ro.it I '■rtaiioiix Hpii/t and the folding up of the Mosquito Range. batHa ^cii"' ncff PO'Sifi Cotoraeit /T-vytt^anffV McifuHf fia rigr* '(> A'ani;r and Sou//i /'a> i- as it is today, shoiving result of faulting and subsequent erosion. PlatkLXXXVI. leological DcvelojimciU nf ilie I.cadvillc and SoiUli Park Region, Colorado. percolatinjj; I the prin- ■ reason ol iiiiip sucli a :ally as well m T58 Tlie secondary uplift of Slieeji Mouiif.\in on the ca* tern slope is due to a second p^reat fold and '".tult. - 'I he elevation of Mount Lincoln is the result of the coin- li) m 1 7}H I in the vicinitv of the shore lines. The crystafline and already contorted hedsof the Archa-an doubtless received fresh crumples in this movement. A tninor force also acted north and south, producinji^ fifentle lateral folds alon^ the fo(jthills at ri^ht angles to the trend of the range. These movements were not paroxysmal •59 or siidflcii and \-i()lent, but protracted for an enormous lapse of time, and appear to be ccjutinued in diminislicd force up to the present day. MINF.KAI, DKPOSITIDN. It was during the period intcrveniufj^ between th(.' intru- sion of the eruptive rocks and the dynamic UKnements which uphfted the Moscpiito range, that the original leposi- tions of metallic minerals occurred in the Learhille region in the form of metallic sulphides, though now thevare fouiul largely oxidized and in other combinations. The\- were derived from the eruptixe rocks themselves un(] are there- fore of later formation than they. Their having been folded and faulted with them shows that they must !ia\e been formed before the great Cretaceou' uplift, and therefore they are Ider than the Moscjuito ra • , itself. The depo:::iL.i we- _• formed by the action of perc(jla'ing waters taking up certain ore materials in their passage hrough neigliboring rocks, and depositing them in more c( ircntrated form in their present position. This may ha\ e taken place while the sedimentary beds were still coxered by the waters of the ocean, and the waters therefore may have been derived from it. or the area of the Mos(piito range may have already emerged from the ocean and the wa.ters ha\e been estuarine. The uplift of the Mos(piito range consisted of a series of folds fractured by faults. The crest is formed by the .Mos(piito fault, auf^ther parallel fracture is the London fault. Tl _ greatest movement is towards the center or Leadville region, dying out at either end north and south ; the greatest displacement is lo.ooo feet. Whatever cliffs may ha\e (originally been formed by this faulting hax'C been planed down b\' glacial erosion. ORIGIN' OF r.EADVIM.K ORK DF-'.I'O.SITS. The ores are deposited for the most part in the blue lime- stone of the Lower Carboniferous. As the ores were de- posited by water solutions, the soluble limestone beds would be more easily acted upon by solutions than the sandstones and shales composing the other locks of the neighborhood, which are less susceptible to percolating water. The Paleozoic formations in America are the j)rin- cipal repositories for lead and silver ores, not by reason of their geological age, so much as by their containing such a quantity of soluble limestones and being physically as well aagj i6o as chemically favorable for the reception of mineral solu- tions. 'I'Ik- physical structural conditions of Leadville are par- ticularly favorable to the concentration of percolating^ waters in the blue limestone, (ireat intrusive sheets of porphyry follow the limestone persistently, principally on its upper surface. 'I'his porphyry is very porous, and full of cracks and joints, alTordin^ reafly channids for water from above, and also channels for ascenrlin^ water from below, al«)nfi^ the walls of the fissures, through which it is irrupted. Such waters passing tin ou)j^h a medium ol dilTerent compo- sition would be reafly for a chemical interchange with the limestone. COMI'OSI rioN Ol' OKKS. The ores were flenositcfl originally as sulphides, 'i'his is shown by the fact tliat the oxidi/c'd ores near the surface ()ass down with depth into sulphifles. In Tfn-.Mile district these oxidi/ed ores are seen to result from tUr alteration of a mixture of galena, pyrite, and zinc-blenfle. There is very little gold in tlu;av»'rage Leadville ort.'s ; what little there is comes from the Morence niine (native gold), anrl from others where it is associated with pyrites. It is usually as- sociated with porphyry rocks, and a porphyry commonly called pyritiferous porphyry shows gold to exist dillusefi through the pyrites disseminated through its mass. Si'k'er occurs aschlorifie, a seconrlary condition, its orig- inal condition probably being sulphide. Z,^rtr/ occurs as carbonate anfl sulphate and, deeji in the mines, as sulphide. Specim(;ns are common of galena noflules surrounded by a thin coat of sulphatt!, and that again by a coat of carbonate, showing the order of transition from sul- I)hide to sulphate and thence to carbonate. In the iron mine native sulphur occurs as an alteration product of galena. Iron ■.\\\i\ tnniti^dfiesi' covx^iMwU" rather a ganguc material th.an an ore. 'I liey are hydrated oxides and protoxides. The iron was originally deposited as sulphide or p/yrites, but has been wholly transformi'd by oxidation. /.in( is not common, but occurs as calamine (zinc silicate) in needle-like hairs and white crystals in cavities in the mines. Its original form was zinc-blende (zinc sulphide), as shown in the Ten-Mile district. The earthy minerals, alumina, lime, silica and magnesia, are in fair proportions, as might be ex|)ected from ores which are a re|)lacement of limestone in cU^sc connection ft^ifi ^ .«WHMW*\ olu- ):ir- <>i "II I of Olll i*\V, Irrl. )')- lit- witli pin |)li\ TV. 'Ill*' ;ill\:iliiic cIciiuMit iiinoiij^ the ores mij^'lit also hf t ia( (.'(i (o tlu- IiiIIul'iicc of tlie latter rock. The aj^n'iits of alt(.'ratioii were surface.' waters, which con- tain evervwhcrc carhoiiic acirl, o.wfj^en, orj^anic matter, chlorifle of sodium (common salt ). an(l |)hos|)horic acid. The rocks through which these wat(;rs passefl, such as |)or- nhyries and limestones, were found to contain phosphoric cid and chlorine, whih; <»rjjjanic matter exists in the hliie ■ mestones ; and in the ov(;rlyinj.f shales and sandstones arc 'uany carhonaccous l)«;ds and even heds of coril. Water passing throu;.(h these rocks would take up all these tde- menls and he nafly for chemical reactions. f/(?A7/oth alouj^^the line of contact and hetween tlu; porphyry and limestone and also in the heart of the ore depcjsit, is a decomposition [Modiict frf)m porphvry. It consists principally of hydrated silicate of altniiina derivefl trom tlu; feldspars (d the p(n'- phyries, perhaps at the time when acted upon hy sulphurous, waters, which hrouj^dit in the orijj;inal oie deposits. t ■.j iccent cax'ities. luvitc is Common, j.(enerally associated with chloride of siK'er aufl manj.ranese and is lorally rcco}inizi\{ as a si)^n of rich ore. \lnl)l. ()!• |(»U\I \ I ION 01 l,i:.\l)\II.I,K (tKI. l>KI'osrr>>. 'I'heores were depositerl from water solutions h\' a metaso- niatic interchaiif^'^e. /. <■.. suhstance e.xchanjj^efl for sul)staiu:tr with the linu- 'oiu- ; aiul lastly < .• orij^inally as sulphides. 1' — • % ! r Miiu'ial iniilfcr is caniffl fmin i ,H' phx'c jn aiiothci w itiiin the earth's crust l)\- liraf anrl wattT. <>r tlu-sr cumhiiu-d. MiiasDinatic iiitcrc liaiijj^c <»l imtal tor limi'stoiu" and tlic rem<)\-al of (loloiniff could only lia\ c l)»'rn prorlnccd i)y water. 'I'lu.' oil's wcic ;/(>/ deposited in />ri-i'v/sf/Hi^ iin'///is, but are a replacement of the k'onntry rock. /. <-., doloinitic hinestone. The ores ^M.ide oil j^Madnall) into ! he material ol tlie linn- stone, with a delinile limit, as would n3 tlic walls of the cavity, as is hi-autitiilly slmwii in >4:fuflcs liiu'd with a sm •.-cssion ol /i-ulitcs m with hiMisot clial- Cfdoiiy. <»[)al and (|uait/. No siicli sucti'ssivo arranjjfLMront in layers is toijiul in the I.cadxilk.' ore bodies. A^Min. (-onid such laijj^i-, open cavities have existid lor \<>u^ distances without support between the layers ot por- phyiN? Why did not tlu'se porphyry sheets close tojj^ether? Aiifl lurther, howcould such extensixc ca\ilies liaMheen formed and ki-pl open undi.-r a pressure of lo.ooo feet of rock, which the jj;eo|oj^y of tlu' rejjfion shows to lia\i' existed aho\"e the fleposits at the time tliey were heinj^j formed? Such ca\ities as we do I'md in the n-jj^ion are all ol \ery recent orijj;in. cutting; throuy^h both limestone ai\d ore bodies, and ha\e been bollowi-d out by surl.ic*- w. iters more lecent e\'en than those which produced the secondary alter. itions in the ore bodies. 'Ihe ore deposits of 'l"en-Mile district .d)ont Kokoiuo, not far north from Lead\ ilk-, are \ery similar in chara( ter to those at Leadxille. Thev occur, however, in a somewhat hij^her di\ision of the ( arboniferous, .ind the ores as a rule are not so decomnosed and o.\idi/e:l, and the transiti(»n from the orijj^inal sulpliifle character of fhe deposits totheo.xi- di/efl Condition is more easily shown. Ki:i) ( l,ll-| «;n| I) Kl.l'nsilS. At Rv(] riitf, still further north of I.eadville. in the N'alley of the Kaj.jle. the s.inu' j^eoloj^ic" s .ries are lound. penetrated, as at I.eadville anrl Kokoino. by eruptive sheets. In the limestones at contact with the porph\ ries, much the >iime classes of ore depintc in his (icology. ASl'IN OKI |)| I'o^l I s. I'hf AsptM niininj^' ri'j^ioii is jj^eolofj^icaljy trlai"l i\\r old island ot ihf Sawalch. oiii' on tlu- cast, tin- other on ilic west, opposite one another, hnt ahont 50 miles apart. The ore di'posits occur in the same general hori/on. vi/., t he Lower (arhoniteroiis. Both rej^fions show intensi- disturbance, both l)\' N'olcanic intrusions o| igneous rock. loldiiij.r, and tanltin^. The pro- i'ess ol ore di'position in hoth rej.(ions has heen ii;i actual replacement of the country rock hy \'ein material. At Aspen the ore is not found in lUtuiil contac t with the o\erl\ iny: erupti\e ij.rneous rock, hut at some d-pth down in the limestone, at a zoiu' where the " blue limi's'o distinct uplifts of the Sawatch ranj^e on Ihei-ast.and the l'!lk mountains on the west, and has been successivelx' atlected by i-ai h uphea\al. The Sawatch uphea\al was a ).fradual elevation of this mountain mass ri-sultinjj: from a j.jradual suhndence of the adjoininj.f sea bottoms, which taused t he sediicicntary beds deposited in those sea bottoms to slope up at N'aryin^: anjj^Ies all alonji^ tin* ancii-nt shore line toward the central m:\-s of the Archa-an isl.ind. Tiie KIk Mountain ranj^a'. which extends to the west and south of t'"s rejj^ion. was u|)hea\'.'d lati'r than th.e Sawatcli. wilhf^reatn \io|ence an(Uru|)ti\e enerjj^v. and the uplua\al was accoi))) inied by cikhmuous intrusions of erupti\'e rock uhi'h wtre forced into the sediinentarv strata alreadv shattered by the lorces of upheaxal. in j.^H'at " lac( olites." or solid masses, and spread out throu>j;h them in e\ery direction in the form of d\kes and intrusive sheets. The )1 w surface exposures of thesi- i^^neous bodies co\'er areas < twenty-five to thirty scjuare miles, and their extension belo the surface is doubtless very much f,freater. I -vSiBIrt \0(} I I » ll I •! MK ll I III II 11)1 i|lN masses III iMiri^n iiMltn niiist ii<>l olilv li.i\r ^H'.ilK (Ii^IiiiIhiI ihi ImwIs williiii iIh' I (7411111 III II |i lir.lV.ll. lilll .iImi Ii,I\< S.I I \|i,ll|(lr(| I III- \ I >lnmf I il I ln' 1,11 1 h s ( I list III this .inM ;is III I Miisi .1 s('\(ii l.ilri.il |iii'ssiiii III ilir .III ji lining ir^imi. Tli.il .iil|i 1111111)4 irL',iiiii W.is ,\s|Hii .mil Its iiriLjliln i| III i< xl, h u I mill III' |iis| ill I III' s| I i|i III srijiiiii iil.ii \ Inil'. .1I111114 till' ,\s|>rn Mniiiil.im 111I141'. wliii ll Is li.ii Kill li\ ,1 |iii iji'i I III); |>iiml III llir nil \ irldlll); S.IW ill ll .\li li.r.ill. 1 ll.il lliis 11 iiii|iii'ssii 111 wnnM !tr iimsl sr\ r|il\ li'll, I lir S.iw.llill j.',l.llil|i' lll.iss .11 1 1 1114 .IS .1 I II lilll III irsisl.iiK (• .Ij^.lllisl llir mlriisr l.ll r 1 .1 1 i 1 HII | il fs- s|iili I .iiisi'il li\ llir \iiim^ri I'lk M-.iml.im ii|ilill. i^ :;^ llir SI liiiiiriil.ii \ lulls |rs||||)4 "" !_^ il^.ljlisl 111! AicliiiMii ( III irs|iitM»l f^ ^ )^riiri,ill\ . uitli slit;lil ilillrirncrs. 5 X In lliiisi' III I 111 s,, lilll iViiK .mil ii X l.r.liU llli' li'l^liill 111 ,1 silllll.ll |iitsi I < limi. ^ tZ llir l.illi I will' ilr|>i islli ll ill .1 P •""" |MI I i.lll\ I III ll isril l»,i\ . Ill i\\ 1 I iiis| I I III 111)4 I III Si >I|| ll I '.II k ll.lSlll. I 111' liilliH'l iiii llir Wisl sulr m| llir ,\ii ii.r.iii isl.md III ,1 null 1 ,mil «|rr|(ri sr.i. iiliil oil lliis ursli 111 s|ii|ir llif Im'iIs ,iu' j^riHi.illx nun li lilll kri I li.m I hose ul i i n irs|ii mil inK K''"'"^" ■•' li"ii/i"i' I'll IIk' <'nst. Ml' \ Mi.lMI'll\ III \s|'l \. I . llir III i| l/i HIS |i'|iirsi'|||i'i| .lie 1 In- I |»|iii < .riiliii.m «|ii.u l/ilrs. 2(J<) ft'Cl. |i's|mj4 nil llir All li.r.m ^t,\\\\\r. i. Slim I. Ill silii n Ills liiiH'sli nil's .iinl i|ii.ii l/i(i's. ;,|() Icfl . \. |),iikri liiiH'sti mrs. iiis|\ .>%:■>: '^^ ':^} ^yy /\ \' Wf ^ ■^ '•?;-: -H.^J w V>J Ok -jV ..-.« a / h '■« rl-.l I J 11 |6.S brown aiifl floloinilic at base, hliu.' coinijact and pure mi lop, 240 Icct. ('ilicsc arc Lower ('arbonilcrous.i 4. CarbfJiiifcrous clays and sbalcs and tbin Ijudded liino stones, 425 feet. Tbc'sc bclonjj^ to the Weber ^nifs i Midrlle (arbonilerous). 5. A series of \ariej^'ated fjj-reen and red sandstones, claxs and shales, some limestones and vv(\ sandstones ol the I pper ( arbonifcroiis, 6. Heax'v bedded red sandstones (Triassic). Above these asjfain are several thousand feet of Cretaceous strata, up to (he base ot tlie Laramie coal l)eds. ('I'he (reta- ce )us, however, and the Jurassic do not re;. I imnicfliately upon the /j^ranitei. Ih'orih'. ()n As|)en Mountain is a bed ol "white poiphx- rv " (fiiorite) in the black shales, 60 to 100 feet above the top of the blue limestone. It is 2A0 leet thick on the slope back of town, but I hickens consideiably to the south, and is traceable to Ashcroft. It apjiears to extend also across the \alley of Koarinj.,' l'"ork to Smuja^/.,dei Mountain. Small inlrusi\f sheets also occur in the lower cpiart/iti-s near the point of Aspen .Nhjuntain and on the east lace ol Kichm'-i)f| llill. As affected b\ the Sawatch upheaxal, these beds wrap around the Arcluean mass, resfinj^^ a^^ainst or dip[)in,t( away from it at varyinjr anj^des. The (piartzites and limestones cross the \alley ot Roaring Fork from Smu^jj^U-r Mountain to .\s|)en Mountain, strikinj.f northeast and southwest, dippini^ mut hwi.'st. 'I'he a 11^4 le ot (lip is about 45 . varyin;.; fiom a minimum of 30 to a ma.\i- mum of 60 in '* Hats " and " ste(!|)s." rill. (tUI. linlUKS. The lower carboniferous "blue limestone" is com|)a( t. homojj;eneous and composed of pure carbonate of lime. The " brown " or "short" dolomitic limestone is of a dark s^ray color, linely crystallint-, finely f^ranulated and tra\t rsed in every direction by a network ol minute \einlets containinjr iron salts, which, when oxidi/ed, color the surface a rusiv blown. The oxidation a Ion j.^ t hese minute veins makes t he rock break easily into dice-shaped fragments ^i\in^ t he rock a "crackly " structure, hence its local name of short lime. (hi' Diitrihiilion. The outlines of the ore bodies c mnot he detected by tlie eye, owinjj; to the tjradual transitio-i troni ore to country rock. The ore is not conlined to the brown dolomift; below (he i6(; S()-c;ille»l coiUacl. hut several ore bodies extend 20 or ;o leet al)ove tliisc'oiitaet into tiie blue limestone and in some cases follow the lines ol cross-fracture cnfiri'i\- across the l)lue limt'stone. The ore is not confined, either, to a d"linite plane or con- tact between two dissimilar l)eds ot Jiuu-sione and dolomite Irom which its solutions ii.t\e ealen into tlu" underK inj,^ do|(»mile, lor in the first place there is no! one si nj^jle con- tact, but manv; and if this so-called contact const ilules an essential condition o| ore deposition, theri- is no icason why it should be conlini-d to tin* one and not lound in t lie others where the rocks h.i\e the same cc imposii ii .n. Ai^ain. on-- bearirif^ sol ut ions would not he lil.ir Rid;.fe and continues down with the dip in the underj.jround work- \i\jj;, hut ore bodies cicc iir ahlane called the contac t. In ot her |)ai ts t heic has been tract urinj.; across the heiit be- tween the p.nallel heddintj^ planes. This would happen if these solutions derived tlieii metals from tlu; overlvinj.,'^ |)orphyry, for it is separated trom the limestone bv arjj[illaceous shales which wmdd be impervious unless fracturi'd across the beddinj^. The analysis of tin* lime mud at bottom of the cave shows by its preponderance of alkalies, which do not exist in the composition of either brown or blue limestone, that the waters flissolvinjj; it came from the port)hvr\. The waters brouj.jht both alkalies and sil ca from tlie porphvry. and probably the iron and baryta, r^ J iMil.nMI I I/A I liiN. Tin's is a scrondaiv process upDii llu- blue limcstniic l)y inagiusian \v;iliis. which is proM-rl by irn'j^nilar t<)ii>j;iu's of doloiiiito cxtiMulinjj: iij), into and across the blue linicstoru'. The It'iiticulai bodit-s in tin- Diirant clitl point to the same fact. 'I'hf crarkly stiiKliin' ot ihc blown hnic results lioni the replaceivjeut ol a molei iiie o| lime by a inoiccujr of maj^Miesia. iiu'oh in^^"- also a contraction in \ohiir,r ol the rock it>cll, which W(»iild cause it to sepaiair \\\ anj^ular Iraj^- Mients. the intersections rilled by mati'rial more soluble than the rock itself. The maj^ne-ian waters may have been connected with those which broni^hl in the vein materials. In the ore :>odies the partially minerali/ed rock on the borders ol (he ore is chaii;.^ed to dolomite, Iu-ihc dolouiili- /ation either preceded or accoinpaiiit'd ore deposition. Mr. l'!ii!iMons su^'i.i^est s ,\s />/ (>/>(t/,ition. In the vicinity of Asptn .Mountain ore boflies, the strata appear to ha\e been s\nchnallv fohh-d and faulle(l between the main Archa'an area on the t-ast, and a mass ot granite at the westtMii e.xtiemity of the mountain, thus pioducinjf a second series ot oppo^itelv inclined beds, also crjutaininj.^ a few ore l)odies. Intrusions ol altered erupt i\e diorite o( cupy a prominent position in the interveninj^ trough and m.iy ha\e seriously faulted or dislocated the strata in the dejiths. The bulk of the Aspen ores are lai>;«ly o.xirlalion produt ts of ai>,nMitiferou^ minerals with trm- sil\ t-r minerals, associated with cahspar and baryta ; it is a "dr\' ore " ro<)uiiin).r to he mi.xed with silicious lead ores before it can be Heated. Such rich ores as polybasite and brittle siher occur also. A jj^reat deal of the ore consists ol line jr mined stei 1 j^alena. \'erv rich in siKer. ASIM'.N AS A I'KnsiM'.f I |\(; ckofNK. .Xspi'ii ajj^ain is an example of a rej,don that had often been sl-hii)iiiii nwv by the piospi'i tor and ab.mdoned belmc the final tlioroiif^h prospecting; re\-ealed its j^reat riches, \ears 171 ^.\fr^> sonic |)r(ispi'(t()is fomul sijj;ns dI • ll.i.it " ;in(l • blnssDin " cropping' out iiiuk'i the l)liu' liiiR'stoiic ol Spar Kidjj^i*. They {■\ru went so tai" as to sink a.i iiuliiu- ol a hundit'd l\ i-t or nioic l)nt thoiij^di tlir\ louiid oic, its chaiac tn was so low ijfradt'. that the mine was lor a Ih on tlu-ir incline, and then oiij^rinated the celebrated " apix and side lin«' ' lawsuit. The oiijj^inal locators had the apex on the outcrop. I hev therefore claimed the whole moun'ain. .i.iil tried to rhive out the side line men. I*'inally a compromise was cJ'ertt'd, hut that t)orin^f d /, ///it:s.\a'///t ///." .\ ditiu^t-rous piecedi . ' and e!\couraL;emeht to that olten ruinous policy ol rum.' ^ I'Mi^j; cross-cut tunnels to i iit an ore horly at de|)th, will' ii his only |>ro\ed indilferently j^ood n«'ar t!ie siirlace. I". Ihi- tallacy we ha\-e beloie alluded to, o| the improbable [o ot- dtilify of " 1 ichnes', increasiii;.^ with depth." \\ l-.N Wll'l 1! I'KDSI'IC IINC,. Now Mi|ip(»sin,t: our pros •untor was the lirsi i.mii to .iiter that re>4[ion years aj,'o, \Vh. t simis weretheri- to Nad I :ii to think it was a ^jood piospeclin^ ^;rounfl .' Supposinj; liini tt^ be laiiK \'Msed in ).,'eol (»•.,", \u' would have not"' "d. as he <-ame deiwr. over the Sawatch raiij^e. that the I'aleozoic strata he hafl obserxt d as ore-bearinjj[ at Lead\ille, out- (ive rock ci instituting the I%1k ranj^e ; fhirdlv, he wo'.i!'! ol)S'Tve the u'j;j,,n was much disturbe-', that the strata were intt-nseis folded, and intenselv laiiUed. All these sijrns lie would h i\'e conssder'-d likeh-. TIumi after following; up the \arious creeks, he would select such spots as where he saw th' massive blue liinesioiu- out- Ht XvrVCa-fHCMMI Miliiiif ! I' I h 7:: ill- utjiilfl re;i(lilv liiul this hfd tiom its U'lation (• Woulfl II to till' t,n;mit»' aiui Cainl)!'!;!!! (|ii;ii tzitc hi-low look Inr pl.ii I's uhcMX- poipliyiv w.is iiilnidcd into the liiiu- stouc or whciL' jr»c;it masses oi it lay al)o\'c or in \icinity of the limfstoiir. This woiihl prohahly lia\t' led him, on iirar- inj,r AspL'ii Mounlaiii to ^iw that iiioiiiilain moic than a [>assin^ look. He would notice that the strata on As|)eii Mountain were \<'ry mueli disturbi-d and laulled.that a spur of granite, (juite out of place, came rij^ht up throu;,jh the middle of tlu- mountain, that strata were pitchinjj; in \arious directions oH from this, aiu! moreo\ t-r that in the lap of this lault-fold was a \ery thick hi-d ol por|)hyry. Me would obsei\'e the line of chanj^i' from tlu' hlue limestone to the dolomite, and at that line he would have piospeiled and found and followed up the " l)lo>soni "at t he line. consi>t intj of calcite aiul haiNta runninjf in a rusty line, liki- the out- crop of a Coal seam, all up the side ot Spai (iulcli and >o \\c would ha\i' disco\ered the ^neat Aspt-ii oie-di-posils. .md hv followinj^ up the indications alonj^ tlw outcrop and loratinij claim after claim as aloiijj;' an outcioppini; coal seam, he couid h .\X' secured |uacl icall\- 1 he whole ••a|)i'.\ " of the hill, and 1)( /ome master of the mountain and all it contained; but had he known then the liti}.,^aiion of 'side line and apex" that was to arise, he should ha\e tjone lurther, and located claims co\erinjj^ the si 173 prise, l<) assist him. ;iii(l fiiUTs somr ol tlic cLiii-.i, m tlicii namrs, to pn-voiit tiic (ii>(i)\crii's hi-iiij^; iiim|)»(l i)\ ;• IhikIi- of piospt'itois \vhi> press ill as soon as an\ tliinjj; is tMimd. (iixxl a(i\i(i' to a prospector, is to kroi) \crvslili ai-.d ■imim" about his (h'sco\»-rifs until \\v has wt-ll Sfciircfl thtin, .ind to he very careliil how he •• « ipeiis his iicad ' to aiiv one. ( "oiii- inoiily a prospt'ctoi u ho has '•struck it," comes into to\v!5. tills up w ith whiskey. " blows it in." and I hen. " blows it oil " ail over town .lijout his discovery, and is elated to find him- self the hero ol l!ie hour. Tlie r<'-nlt is. betore d.iylii^ht the lollowinj.,^ mornin<.,^ a hundred men are chasi'ij.- '.i/e another in the direction ol his discovery, and bi-lore a da\ or more is over, the mountain is co\erefl with locations as close as jj^ra\es in a cit\' churchyard, and in a week's time these locations ;'.re covered attain by a seiond layirr. as tlie >a\inii is, "several feet deeji." A boom tollows. The olfscourinj^s of the counlrv pour im witi) the saloon, dance hall and j^andjliny; hell element. .\ murt course in such a jj^.unbliny speculation, by such pru\riii's aif finiiid to he intTcK stipfilicial, I he hnum iilti'i ly lollapst-s, and I lie drcai v •sij^lit is stjcn a litllr lalcr. ot a flesulalc xillaj^^c. witli lianir houses an bflakrn "< // in ijriif/ii SiU/s. In III f minmj^M'iij^nufci thev yiv t- somr suit o| all idiM as ti> what llu- puipiity may Ik- liki' As to its \aliM', flc, t hat lie proixiscs to liiid nut tni hini- sfll. 'riif ( ompaiix sDiiifl iiiu-~ asks liiin In fxaininc wit li a \ir\v t<» Nt'iilyiiij,' "i modify iujr ,,r < nnl iadi< liiij^^ such ic- |MlltS. Thi" it'j^noii. the ( tuinl ly, the tharaclfi o| Hu- (li|)o>i|s, | he loral coiulilions. may in all prohahility he comparatixcly new or stiaiij^T to him. I'rior to slaitint,' he mav makf iiii|uirics ill miiiiiiL; circles it aii\ t hiii^'^ is known about the icj^iniior distiiit. It thrri" an- any puhlishcd mininj^; or jri-oloyual reports (»i maps, he will consult these. j-inalK he st.nlsdut with as jilth' ha)4j.;.i^c as possihie. usual!) .1 small h.md li.ij;;, ('onlainin^ .1 h-w ncct'ssaries ; a tapelini', j.;eo|()j.rical pick.. clinometer and compass and note 01 sketch honk. Ilisduss is gcneially a suit o| (oiduroys. lealhei j^aiteis .md sir..u;.{ hoots. .\s he enters the rej,don h\ rail 01 mi h,»i sehack he notices the lu.iiii j^folojj^ii .d tealuies, uhi lliei the io( ks are j^i.iiiit ic. sedimeiilary. 01 eiupli\e. I''iiiall\ he hmcIu-s iIm- (amp. calls im the ownei oi supei inleiideiil and rides up uilh him to \ isit the mine. Il he shoidd " la\' o\ t'l " lot the allri- iiooM in the \ illaj.ji\ he may as indire( tl\ as possible tr\ to pick up any tjossip there mav he alloat relatinj,^ to the property, lie is at oiu'e impressed \vith the accessihilit v or inacct'ssihililv ot the pro|)erly, ami estimates the pioha- l)le cost ot lninj.^iii)4 down the oie to the mill or to the i.iil- way track, and ohsei\es the proximity 1 u' ahseiu e ot timher and water powi-r .\t last he rea( lies the mim-, iliiies ai I he hoaidiiiL,' house, and is iheii takt 11 o\ci the |)ieniises l)\ the superinleiidenl. Mis llisl attention is diie( ted |o the sur- face character <>( the piopiilv, its lopojj^raphv , whether roljiuj.;. smooth or pr«'cipitous, wheihei it is hij;h aho\c the \ .illi'y tir m-ar (low n to il. whether the mine is hij.,di or low- as rt'jji'ards the water le\tl (U drainaf^'e system ol the iieii»h- hoihood, whether the piopeilv is con\ ('nieiilh situ.iled tor workiiiff the mine and transport inj,; the oie, etc. Accessihili; V is an important matter. In some reyions,. such as in tJie San ju.in distiict (Color. idol lor e.x.imple. mines aiul prospect holes an- sometimes on the top or sides ot mountains 01 pii-cipices, thousands ol leet aho\i' the \allev below, located at spots oiu' wmild t liiiik (mly.iiieayle Could reach ; prospect tunnels, too. .ire diixcii wliei»' there appears scarcidy a h)ot hold for ; stpiirrel. No spot. howe\ t-r. seems too inaccessible lor the juospe' loi. .\( a ijlaiK c I he -^ 176 II I j . i 'I , I 'H m ! ' B II S c n ■fi '6 I y, 3 n n if b E 177 viiKint'i-T s«'fs that in a piMpnts NJliiatrd in mk li a icj^iun, ;u'rr>sihility is mu' i>l the tiist and oltcn iiimnI !■ ii luidable pi°itl>k-ius to l»r ('i>lisi(lrt'«'(l. 'I'm sonu' ol tlii'sr mini's air loii^ /.i^/.;\^ tiails cnl in the side of tilt* inonntain. Tht- (-n^^int■(■^ calt iilatfs how nuuh tlif iiwncrs «)| (lir (l<»nkcv ;nr« ih.a a mint* at that almost inacccssihir hci^rjii, on^^ht to carry a j^rood (It'll ol pii'liy hi^h ^fiadt' oi»' to pax ••\»'n lor traiisnor. lalioii h\ till' '■ hiiiios, III aloiu' ihccost ol height altcr- wards to distant sim-ltiii^r works. ( )ii ihr other hand a mine I ey or ' un ■ • ' ^ ■ '■•• • --••■ whose w«»rkin>^'s oiu-n ont within eas\ .ict cs*. ot ihr \ ;i railway tra< k. ( onid allord lo c.iriy le>s vahiahle ore lIuTC is timhei and wati-r power to he eonsiden-d. the lormer lor timherinj;^ the workings ol the mine, the latter l"r sneli a mill, under a developed piopnlv ; 11 there he a mill oil tin- |)ieniises. he will e.N.itniite and report on its capaeitN and siiitahility tor tieatini,' the oris. A mill site must, ot C'lnisc. he selei ted (lose to some water power. In soiiK' diNliiets there is a Mipirahiindam e ol water, in others ;j serious lack ol it. or the supply is nK'af;;re at ceitain sea- sons, or is lio/fii lip in winter. Some mines are rich an average for the general 1 un of the mine, or as not imjiossibly being " fixed " for him. If he suspects the latter, he will take a sample or two to see if the mine has been tampeied with, taking a little oi this out on the dump crushing it and washing it in an iron spoon. If a very astonishing amount of gold c(dors show up, his suspicions arc aroused. The judicious miner does not generally want to salt too heavily, for fear of the enormous results exciting suspicion, but despite his care he nearly always salts a little higher than he intended. In a mine where the rock is hard, a miner may salt by drilling holes and inserting mineral or ore and disguising the hole. In loose ground or one full of cracks, a shot-gun loaded with a moderate discharge of gold-dust will do the work. The skill of the miner in this case lies in his choice of a spot where he thinks it probable the expert will take samples, ov in coaxing the expert to take samples from such ground. In hard ground the expert may avoid such salting by having the work blasted out in his presence till a purely fresh, \'irgin face is shown and then taking his sample. These precautions are not necessary under all circumstances, but only in such cases where the expert has a suspicion that there is an attempt to " put up a job " on him. After getting nis samples, and as many as possible, he will sack and seal them then and there in the mine, and never lose sight of them till he has expressed them to his own home. Sometimes a mine is so timbered up, that sampling is ditRcult. Now as they go down the shaft, it may be the expert remarks " I should like to take a sample in this shaft, but it is so timbered up that I don't see how we can do it without ripping out some of these boards." " Why of course, so you oughtter " says the miner, "and see here, I think this board is loose." Now beware lest that board was purposely loosened and behind it the ground is salted. By taking a great number of samples at comparativel)' close intervals, provided afterwards the samples are not tampered with, the expert is less liable to be deceived by salting, than V^ if 17 f! if he took \er)- frw. A mine cannot be salterl all over fvom eiul to end if it is a larjj^e one, only at judicions inter\-als, and it will be bard if tbe expert does not escape some of tbose interx'als aiul >j;et some true sampli's. Besides taking bis rej^ular assay samples by ciittinjj; all around tb.; wal's, roof and lloor of tbe tunnels at intervals of five, ten, or twenty feet, accordinj^ to circumstances, crusliinjr, and quarterinjj; tbe debris, aufi finally sackinjj^ and sealiiif^ bis sampli' bajj^s, be sbould occasionally take a "j^rab sample," or a bit of rock at random, or a small sackful from tbe jj^reat mass of bis sample, and put tbem in bis coat j)ocket, and keep tbem on bis person, to act as a reference in case of any possible tampering or accident to bis samples wbilst in tbe vicinity or in transit. He sbould also take bulk samples, ^ood sixcd cbunks of uncrusbed rock wbicb sbould ajj^ree with tbe assay results of bis quartered samples. A disadvantage an expert is under in a strange camp, if he cannot take bis own assistant with him, is, that he is very much at the mercy of the miner, if any hard work has to be d(Mie, such as blasting or bard fligging. Whilst engaged in such work tbe miner, if be ple.ises, has man\' chances of scattering around a little gold-dust on the rock of tbe vein or tiie loose dirt of a placer. Whilst gold-dust is the favc^rite medium for salting a gold mine, chloride of gold is sometimes used. The latter, how- ever, is rather a dangerous and barefaced trick to try on a competent expert, as its qualit)' can readil\' be detected by the chemist, it being scdubic in water. In a case of this kind that came to our knowledge, an expi'rienced expert liad examined a certain mine and condemned it. Later, the owner who was an honorable man, asked him if, as a special favor, be would re-examine it, as in bis absence tbe assa\' values fnjm the mine had of late shown much better results. The expert reluctantly consented to do this, though con- trary to his general rule. In going along tbe workings be noticed here and there on the walls, certain patches and streaks of clay or mud, be had not t)bserved on his first visit. Guessing what they were, he casually observed to tbe miners, "Seems to have been raining in tbe mine since I was here." However to the great delight doubtless of the miners be took several samples of these, and forwarded tbem to a reliable chemist. The latter pronounced tbem chloride of gold. This of course gave tbe salting scheme away as chloride of gold does not occur free in nature, much less in a mine. Tbe owner of the mine was exceedinglv I. Si :inj4:rv wlicii lit- Icarncfl wliat the miiu.Ts had done williotit his knowlcflj^'o or coiiiiivaiiCL'. 'I'lic im-ii tlioiiiscKcs l)ciiij^' coininoii ly niori; or less iiitort-sU-fl m the sale ot a lume, arc apt to try and sah it without any <'oniiivaiiCt' ol t hi" owner or siipfriiitciidiMit. We hi'ard ot a case in the San |uan rUstrict where a mine tliat was fairly jrood was about to l)e examined. This mine canied occasionally s|)f(iinens of the \ery rich ore, called ruhy silver. Not satisfied with the lair, natural richness of the mine, the miners must nei;fis import into tile hole, (|uantities of ruhv coJU'cted from other mines in the flistricf, whose men were of coiirsi; in svmpathv with the scheme and probabk- sale. This was acting' without the knowledjj^e of the owners. SAI.I'INC. (lOI.D iM.ACKKS. .\ltlioiif.(li a fj^ojd placer usuall)' coxcrs a \ery h\\^;c area of jjfroiiiul, it is possible to salt it. Usually a miner shows up ills placer by openinjic up [lits at convenienf intervals, so as to cover the jiroperty. Xothinjj; is easier than to salt these pits with jj^olrl-rlust. ("oiise(pit'iitly whilst an expert wii! examine these holes and |)an the flirt, he should be on his jj^uard, and insist, where possible, on holes beiiifj^ freshly duj,,' in his presence. Kvcn then he is not safe, (ienerally in a placer, by the cuttinj^ of a stream, sections are shown sometimes from j^^rass roots to befl rock. From such he shcjuld take and pan samples at dilTerent le\els in the exposure, this too, prixatelv and without too much sujier- \ision (jf the interested miner. SAI/I'INC. ASSAN' SAMI'i.KS. This may be done in several ways. If the expert is im- prudent enou-inj4- of samples for others is not an unccMnmon trick. The expert cannot watch his samples too cl<:)sely. lie shou''' sack and seal them on the gr( and, sleep ipo with them under his pillow if need be at nij:(ht,yet even then cases have been known when the wary miner has succeeded in extracting and changing them for bags, to all appearance exactly similar. The samples are never safe till boxed up and expressed and on the way to the city address. He should never fail, as we have said, to have partial duplicates of these about his person. If the expert wishes to assav the ore at a friendly assay office near the mine, whilst ho is grinding down his sample to dust, an innocent looking miner may loaf in, and wliMst watching the operation, accidently upset the ashes in his pipe over the sample. Probably these ashes contain gold- dust, and we might here observe that a single grain of gold smaller than a pin's head may materially alter the results of an assay. Some' years ago an individual who had succeeded in booming a certain placer distiict and getting up an excitement and a rush, constituted himielf as a referee, and professor ; and when miners brought samples for his inspection, the were always found to be very rich in gold. But simila samples from the same spot if uninspected were somehow invariably barren. The wizard's mere look seemed to change the sand into gold, until it was found that he concealed in his finger nails "which wei"e taper" not wax, but fine par- ticles of gold. Hence Midas-like whatever he touched he turned into gold. Whilst the salter may lay traps for the expert, the expert may sometimes lay traps for the Salter. An expert, who had reasons to suspect a certain mine he was examining had been tampered with and guessing there was a likelihood of an attempt on his samples, after securing himself with duplicates, left his samples exposed on the floor of his room : t the hotel, then went out and hired a reliable Mexican boy to watch his room and report to him immediately if he saw any one enter it. He had not long to wait. At dinner the boy tapped him on the shoulder, and he went to his room and caught the miner in the act of tampering with his samples. Sometimes miners, if wealthy enough, will go to great expense to salt a property. Some miners took a couple of Avell-to-do eastern capitalists to a certain placer, panned the gravel before their eyes, and showed up wondrous colors. The investors having been warned of miners' ways, refused to entirely swallow the bait, but told the boys to go ahead and develop the property, and if at their next visit, it show- ed up as well as the pans did on this occasion, they would 191 buy it. When the easterners were j^^one, at a cost, of several tliousand dollars they built a tlunie, put in a hydraulic pla'U, and g-athered a pile of loose dirt to wash down the flume, where the f^o!d is feathered upon cjuicksilver. Tlie " sharks " raised $50,000 for a gold-dust fund. This dust was run evenly over the quicksilver so that when the capitalists returned, there was everything to show an enormously rich placer-ground. The capitalists insisted upon aclean-uj) after the first fortnight's run, which added so much more joy to the sharks. This time the bait was swallowed whole, string and all. The capitalists paid down promptly $250,000 for the ground. The sharks left the country. In a feu- weeks nothing could be found but the amalgam of the sharks. An ingenicjus trick once baffled some experienced ex- perts and came ver}-^ near selling a mine. The mine was a well developed one and had done great things in its day. It was claimed that at the face of the tunnel, or where the workings left ofT, there was still a fine showing of ore in place to go on with. The experts found it as stated; on the face or end of the tunnel there was a fine showing of ore, and the probable amount in place and for the future was duly measured up and estimated. It leaked out later that this block of ore was only a thin screen purposely left, all back of, and behind it, having been carefully worked out and the opening foi the miners ingress and egress skilfully concealed. The mine was re-examined, the cheat discovered and the reputation of the experts saved as well as many thousands of dollars from the pockets of guileless investors. This brief sketch of some of the ways of some miners, for some regions and properties, would give an unfair idea of some mines and miners as a whole, if it were supposed that all miners are given to salting, and all properties for sale are beset by a network of dishonest devices. On the contrary manv, vtry many, miners are as straight as a string and hundreds of properties are to be examined without fear of tampering. But it often happens that a miner, who in every other relation of life, is as honest as the da\', diaws a line, when it comes to the selling of a mine, which he considers " fair game." But, as elsewhere the world through, honesty pure and simple is the right policy, and in the end would be found the best paying one. For the notorious dishonesty con- nected with mines (much more common in the past than in the present) scares away capitalists from investing, whilst Jii I 192 if truth and honesty were maintained, money would roll in freely. One lesson at least may be learned from what we have said, and that is, that if in some cases a professional expert is ever taken in, what chances has a capitalist, ignorant of mines, to buy a mine on his own examination? What man ignorant of horseflesh would venture to buy a steed from a professional horse-jockey, without taking with him a friend who is knowing about horses ? How much more so in such a difficult and delicate problem as that of purchasing a -mine, is it the duty of an investor never to purchase or induce his friends to purchase a mine, until he has employed the services of a competent expert to previously examine it. If the expert's fee should amount to a few hundreds, and after all he should decide on condemn- ing the property, it is far better for the company to entail this expense, and perhaps lose this small sum, than to involve themselves in the loss of thousands of their own as well as other people's money in a bogus, w^orthless, or wild- cat scheme. CHAPTER XV. PROSPECTORS' TOOLS AND HOW TO SHARPEN AND TEMPER THEM. The principal tools a prospector take., into the field, are picks, drills, hammers and shovel. A prospector, esp^-cially when climbing mountains, likes to be as light-handed and unencumbered as possible. For his trip as a whole, i?e may carry several different tools packed on his donkey, but when he has arrived at a locality, the vicinity of which looks likely, he leaves most of his heavier tools in his temporary camp, or near to where he pickets his pack animal. He makes a short excursion up the mountain for a general reconnoitre, armed with nothing more than a light prospecting pick, weighing not more than three or four pounds. This little pick is about ten inches in length, with a handle about fifteen inches long; the longer portion is sharpened into a pick, and the shorter ends in a square faced hammer. We recommend a square sharp cornered face to the hammer, in preference to the bevelled ii •93 111 •e rt a id in face, as the sharp edges and corners are better adapted for breaking rock than the rounded or bevelled ends. This prospecting pick or geological pick and hammer, should be all of good steel, with a good sized eye to admit a springy handle of hickory. See Plate XCVII, Figs, i, i, i. , Armed with this little weapon he climbs the hillside, hunting for " float " oi for rusty outcrops, of ledges. Loose pieces of rock he cracks open with the hammer end, softer rock in place he explores with the pick. " When I am climbing over the hills," said an old weather-beaten pros- pector to me, " I want nothing but my little pick, then if 1 find anything likely ' in place,' I mark the spot, and go on, and at noon I come d( vn to camp, or to where the ' burro ' is feed- ing, I take up my heavy digging pick and shovel and ' open up ' ; this will occupy 'ne till evening at least, then if I find there is a ledge worth more thorough ex- ploring, I leave my tools by the hole, and next morning bring up the drills, hammers and blasting outfit. But the first thing 1 would advise a tenderfoot, is to ge^ /i/s eye iraincd, trained to looking for float and observing mineral signs, trained to the whole business of close observation. Why I 1 myself, old hand as I am, after being awaj^ for some months about town or looking at other things, can't get my ey^ in and down to it for two or three days ; then it kind of comes natural. " You must have an eye for float and rocks like an artist has an eye for color, and a musician, an ear for music. A tenderfoot had better go along with an old hand for a few daj'^s to get into training." Rbcks and Hammers. Plate XCVII. 11^ DESCRIPTION OF TOOLS, PICKS AND DRILLS. Picks and drills are the main tools that need sharpening and tempering. The kind of sharpening and .lature or degree of tempering depend upon ♦^^he kind of work or kind '. m of rock to be worked, whether hard or soft, loose grained or fine grained, siHceous or clayey. Drills, for example, would have to be differently sharpened and tempered for hard vitreous quartzite than for soft sandstone or hardened clay. The same remark applies also to picks. Picks may be double pointed or single, or with a hammer head called a poll, it it is to be used for breaking rock. The main points oft a pick are, strong cutting tips, stout eye and a tight handle. The little prospecting pick is made of the best steel throughout, but in the heavier pick, the wearing parts are the tips, which should be replaceable. An all steel pick is liible soon to be shortened up and useless, whilst tlie iron pick eye, a 14 inch length of best iron, gives long service by welding on tip ends, whenever desired. Professor Ihlseng, in his "Manual of Mining," as also Mr. George Andre, in his book on " Rock Blasting," give excellent descriptions of tools used as well as the mode of sharpening and tempering them ; to them we are indebted for many of the details of this article, and to their works we refer the reader for further information on this subject. " The picks are sharpened to form on an anvil, and commonly drawn to a four sided pyramidal point, for hard rock, and a slim taper for fissured rock, and a bluff taper to cut crisp ground, and to a chisel end for chipping the ground. The eye is oval and well surrounded with metal. All the strain of the pry- ing falls on the eye, which must be true and stout." DRILLS. " The drill is a bar which has one cutter edge and one hammer end. It iS'of round or octagonal steel. Drills may be of various lengths, from a foot to four or five or even more feet. For prospecting purposes two or three medium short drills from two to four feet are generally enough, as the prospector's business is rather to find than to develop. In beginning to drill, it is common to use a short thick drill, with a stout 'bull edge' rather than a thin, tapering one, especially in hard rock ; smaller sized, /. e., narrower drills may be used for increasing depth. " The rock drill consists of chisel edge, bit, stock and striking face. To allow the tool to free itself readily in the bore hole, and to avoid introducing unnecessary weight onto the stock, the bit is made wider than the latter. In hard rock, the liability of the edge to fracture increases as the difference of width ; the edge of the drill may be straight 195 ' ! I or slightl}' curved, a straight edge cuts more freely than the curved ; a bull bit for i^ard rock isgenerally curved, a straight edge is vveaKer at the corners than the curved. The width of bits varies from i inch to 2^' inches. Figs. 1,2, la, 2b, Plate XCVIII.,show the straight and curved bits and angles of cut- ting edges for use in rock. The stock is octagonal in sec- tion. It is made iri lengths varjdng from 20 inches to 42 inches. The shorter the stock, the more effectively it trans- mits the force of the blow. To insure the longer drills working freely in the hole, the width of the bit should be very slightly reduced in each length. Diameter of stock is less than the width of the bit generally by y% of an inch, " The smith cuts up the ' borer ' steel bars into desired lengths to form the bit, the end of the bar is heated and flattened out by hammering to a width a little greater than the diameter of the hole to be bored. The cutting edge is then hammered up with a light hammer to the requisite 1 2 IH^,4. i3 T? f// O :ia Drill In hole in rock. Tt4m COLLttHY CNnrntE^ ;i h rtr Plate XCVIII. Forms of Drills. angle and corners beaten in to give the exact diameter of the bore hole intended. The drills are made in sets and the longer stocks will have a bit slightly narrower than the shorter cies for reasons already given. The edge is touched up with a file. Heavy hammering and high heats should be avoided. The steel should be v/ell covered with coal, in making the heat, and protected from the raw air. Over- heated or burned steel is liable to fly, and drills so injured are useless until the burned portion has been cut away. Care is required to form the cutting edge evenly, and of the n 196 full f^" across. This spot is softened and at red heat, cut open, and swelled by a drift to form the eye. This is then slit at the ends, and softened, while a 6" length t)f pick steel is being heated. When ready, this steel is tongued into the iron, and ham- mered. A reheating with borax, and a hammering complete the weld, after which the picks are sharpened and tempered, no signs of the weld should be visible." " Pick-steel " is a special steel that can be had in bars i^" or 1^" X ^" or |^"and used only ff)r tips. Steel bars for drills come in lengths of about 14 feet each and from ^" to 2" diameter. The American "Black Dia- mond " brand is a favorite. The bars are cut into pieces as long as can conveniently be used, e.jf. 30" and 36". The bits are wider than the tool, to prevent it sticking to the hole. The}'^ are widened according to pattern, so they can " follow " well. The first drill has the widest bit; the followers nar- rower ones. In hard rock the flare is smaller than that in soft rock. "The temper is a lighter color for hard than for soft rock. If the edges of the returned drills are cracked or broken the steel is too brittle, and should be made softer or other coal used. If the edges blunt much by wearing round, they are all right, though a harder temperature may give them longer life. Cast steel borers are never heated above a cherry. They are annealed at the striking end." PRACTICAL SUGGESTIONS AND POINTS BY A BLACKSMITH. A prospector must have something to act as an anvil, a hard pebble wont do, he can carry a small anvil or a chunk 199 of railroad iron. A small iiand bellows or even a portable forge worked witb a crank will make bis cnittit complete. The followinfj; practical bints I picked up from a blacksmith whilst watchinp^ him at work tempering both picks and drills for some prospectors. He said: " Vou must temper your drill according to the character of the rocks. "For hard rock, use a short thick edged 'bull bit' which will stand a high brittle temper such as ' straw.' For picks, a light blue color is a good temper, rather than ' straw 'which is too brittle. Cherry red is the heat of your bar, not hotter ; laying this on the anvil and hammering it well all over gives it toughness. If blisters show on the steel you must hammer it over again. By occasionally dipping your hammer in water and then striking with it, you get the steel down to a fine grain. When you are dipping for tempering, put the point in the water, that cools the point, and the heat runs the color down to the cool point ; when the color reaches the tint you want, then is your time to cool off quickly. The color progresses from a white or pale straw to copper color, to blue. Copper tint is a good one to stop at for a drill, — blue, for a pick. The right moment to stop and cool is just at the turning point from one color to another." He took a piece of steel, heated it to cherry red, laid it on the anvil and pounded it lightly with his hammer all over, to toughen it by blows, occasionally dipping his hammer in the water to " water temper" it : this further toughens it, by par- tially cooling it. Now the bar was again put in the fire and heated to a cherry red, care being taken not to keep the bar too long in the fire, as that would tend to take its toughness out, or produce blisters. The bar was plunged about an inch into the water, and then rubbed against a brick, to show the colors plainer. These passed from the point upwards, gradu- ally through the colors we have mentioned ; to arrest it by suddenly cooling off at " straw,'' would make it too brittle for ordinary drills, except a " bull drill." Now the " straw " turns into a copper hue, a good point to cool off for a d^r///. Now it passes into a blue, at this point it would be well to cool off for -dipick. The edge of a drill is almost of second- ary importance to the sharpness of the projecting corners : when these are gone, the drill is used up, and clogs in the hole. Some rocks like sandstone will, by reason of the quartz in them, wear off the corners very rapidly, others, like limestone or granite, less rapidly. Another blacksmith advised me not to dip (as is commonly done) the point only an inch in water as it is apt in use to 300 break at the water line, but phinj?e it all oyer in the water. " Who shall flocific when doctors disagree ? " A prospector should take with him a rejrular bhu:ksniith's hammer tor sharneniufr, as well as the 4 or 5-lb. hammer he uses tor striking drill or the rock. CHAPTER XVI. SOME ELEMENTS OF MINING LAW RELATING TO PROSPECTING. A prospectt^r would do well to actiuaint himself with a few elements of mining law, so we will give a few samples ;le of the claim. On each placer claim of i6o acres, not less than loo dollars' worth of labor shall be done by the first of Auf>^ust each year, and upon less or more ground a sum in pr(jportion. I TsT D i: X . Algonkian Epoch 26-27 Alteration of Rocks and Ores gy, 161 Andesite Lava 23, 35, 57, 94, 124, 127, 137, 141, 151 Apex and Side Line 171, 172 Archaean Age 18, 20, 21, 39. 96 Argentitc Ore 63 Arizona 95 Aspen Mining Camp 75, 83, 85, 88, 99, 165--174 Augite 51 Australia io(\ 1 10 Manded or Ribbon Structure 87 Barite 52, 76, 161 Basalt Lava 34, 35, 57, 58, 94, 112 Beach Mining , 113 Bismulhinite Ore 62, 95 Blanket Deposits 73, 75, 151 " Blossom •' Rock 88, 171 "Blue Lead" 112 " Blue Limestone " .22, 39, 156 " Booming " Mines 173 Boulder Mining Region 20, 26, 73, 93, 117-123 Bowen Mine 88 Calcite 51 California.. 34, 105, iii, 112, 113, 115 Cambrian 21, 28, 40, 48 Canyons 19, 20, 35 Carbonates 65, 66 Carboniferous 18, 21, 31, 42, 43, 49, 156, 168 Caves and Cavities 162, 163, 169 Chlorides 64 Chlorite 51 Cinnabar 35. 132 Coal - 23, 31 Comstock Mine ..8, 92, 103, no Contact Ore Deposits 49, 73, 94, 151, 169 Copper 60, 61, 65, 126 Country Rock 97 Creed Mining Camp 126 Cretaceous 23, 33, 45, 9^ Cripple Creek Mining Region 12,35,94, 128-151 Cross Cutting loi, 102 204 INDKX. PACE Cross Veins • -86, 87 Dakotah Group - - 23 Decomposed Ores ■- -- 92 Dendrite 147 Deep Leads - .rii Devonian - - 30. 42 Dinosaurs - 23, 32 Diorite 55. 94. 1 68 Dip --- 85, loi, 102 Dolomite -- - 21,51 Dolomitization..i. _ 75, 170 Drilling - - 76, 195 Dykes 50,93,94,100,130,149, 154 Earth's Origin — .25 Ed ucation of Prospector. — - 8 Effusive Rocks - - 57 Eruptive Rocks , 57,94,98 Eureka Mines - 30 Examining Mines — 174-185 Faults 68-71, 79, 80, 81, 93. 153 Feldspar — 50 Fissure Veins 48, 77, 87, 90. 117, 123, 131 "Float " - 13, 14. 88, 144, 145, 147 Folds 28,68,81 Fossils - 23, 29, 30, 32, 33, 34. 38--46 Free Milling Ore 88, 95, iSi Galena - 8, 98, 156, 161, 181 Gases -139 Geography, Ancient 29, 33 Geology, Historical 24-46 Geological Ages 20, 23 Geological Sections 17-19 Geological Training 15 Geological Works -I5 Glacial Action ._ 116, 156 Glacial Epoch 35 Gneiss 53. 54 Gold.- 18, 21, 28, 32, 34, 35, 61, 98, 104-111, 114, 181 Gouge 85 Grand Canyon 19 Granite 52 Grits (Weber) _ 22, 31 Gunnison Region 96 Gypsum 52 Historical Geology. r-24 Hornblende , 51 Horses :7s Hydraulics.. 113 Igneous Rocks ^. ....... .54, 72 INDEX. 205 Impregnations 82, 86, 145, 164 Indications 78, 79. M3. '44 Intrusive Rocks... - 54- 72, 94 Joints • 69-71, 82 Jurassic -25,44 kaolin i 162, 165 Mica -- 51 Microscopy of Minerals I33"i35 Mineralogy - - 59 Minerals - 50, 51, 59. 62, 63, 64-67, t6i Mineral Waters - - 69, 70 Mining Laws - .200-201 Mosquito Range - - ^57 Nebular Theory 25 Nuggets ii» 95. 105. 106, III, 164 Obsidian - - - - - - 58 Openings in Rocks ' V Ore Chimneys ^^4 Ore Deposits-.-.. -. --67, 74, 75- 83, 94. 159- i^o Outcrop - - • ^^ Outfit - 9 Paleozoic, Meaning of - - - - -32 Paleontology - - - - 3o. 39 Panning --- -- i^- ^3. H Pay Streak '^^ Phonolite ^37. 142 Placers. n. 13,35,36, 104-11J, 114. 2or Pockets 9^ Polybasite - - ^3 Porphyry.. 21, 50, 55, 56,94. i34. I54. 168 Pre-Cambrian .26 Pvrites - 62, 88. 181 Quartz 50.181 2o6 INDEX. PAGE Quartz Porphyry.. 55, 56. 57. 121, 154 Quartzite 18, 21, 22, 28, 53, 163 Quaternary . 23, 35 Recent Disturbances - — 36 Red Cliff Mines 28, 62, 163, 164 Rhyolite 23, 35. 57, 94- 151 Richness with Depth 91, 92, 148, 171 Rocks 47, 50, 123 Rosita Mines 127 Ruby Silver 61,64 Saltinji ivlines 178, 185-192 Sampling Mines 179, 188 Sandstones 18, 21. 98 San Juan Mining Region 35, 78, 87-S9, 95, 97, 99, .05 124-127, 176, 177 Schists - 53 Sedimentary Rocks 48,151 Serpentine - - 54 Sharpening Tools 196 Siderite Iron 60 Silurian 21, 28, 41, 48 Silver Cliff Mines 35, 127 Silver Reef Sandstone 33, 82 Soifataric Action 139, 140 Solutions 67-73, 97, 99, 100, 104, 125, 138, 169 South Park Mining Region 20, 49, 81, 116, 151-156 Steamboat Springs 140 Stephanite 63 Strike 85, 101-102 Stromboli Volcano -128 Surface Ores 95, 147, 148, 1 74 Surface Signs - 75. 79 Syenite 53 Talc , - - 51, 161 Tellurides ..i 18-122 Tempering Steel 197-199 Tertiary 23, 34, 97, 124 Tin Ore 30, 97 Tools 10, 192 Trachyte Lava 58 Triassic 22, 32, 44 Tunnels 102 Unconformity 30 Veins 21, 48, 77, 84. 86, 87 Vesuvius Volcano 131 Volcanic Action---.34, 35, 93, 127, 128, 131, 135, 141, 151, 153, 155 Walls 85, 86, 150 Weber Canyon 19 Zinc. 21, 66, 126, 156, 160 LIST OF AUTHORS. 207 LIST OF AUTHORS AND WORKS REFERRED TO. Balch, W. R. } Mines, Miners and Mining Interests of the United Balch, A. ) States. Cross, Whitman. — Geology of Cripple Creek. Dana, J. D. — Geology and Mineralogy. Emmons, S. F. — Geology and Mining Industry of Leadville. Parish, J. B. — A Typical Boulder County Mine. Geikie, A. — Hand Book of Field Geology. Guiterman, F. — Red Cliff Gold Deposits. Ihlseng, M. C. — Manual of Mining. Judd, J. W. — Volcanoes. Kemp, J. F. — Ore Deposits. Lakes, A. — Geology of Colorado and VVestem Ore Deposits. Le Conte, J. — Geology. Lock, A. G.— Gold, its Occurrence and Extraction, Lock, C. G. W.— Practical Gold Mining. Penrose, Arthur. — Ore Deposits of Cripple Creek. Phillips, J. A. — Ore Deposits. Williams, Albert, Jr.— Mineral Resources of the United States.