WfrU' 
 
 University of California Berkeley 
 
Bulletin No. 254 
 
 o f A, Economic Geology, 49 
 Senes U Descriptive Geology, 61 
 
 DEPARTMENT OF THE INTERIOR 
 UNITED STATES GEOLOGICAL SURVEY 
 
 CHARLES D. WALCOTT, DIRECTOR 
 
 REPORT OF PROGRESS 
 
 IN THE 
 
 GEOLOGICAL RESURYEY OF THE CRIPPLE 
 CREEK DISTRICT, COLORADO 
 
 WALDEMAR LINDGREN AND FREDERICK LESLIE RANSOME 
 
 WASHINGTON 
 
 GOVERNMENT PRINTING OFFICE 
 1904 
 
Bulletin No. 254 
 
 a.. . / A, Economic Geology, 49 
 es \B, Descriptive Geology, 61 
 
 DEPARTMENT OF THE INTERIOR 
 
 UNITED STATES GEOLOGICAL SURVEY 
 
 CHARLES D. WALCOTT, DIRECTOR 
 
 REPORT OF PROGREi 
 
 IN THE 
 
 GEOLOGICAL RESURVEY OF THE CRIPPLE 
 CREEK DISTRICT, COLORADO 
 
 BY 
 
 WALDEMAR LINDGREN AND FREDERICK LESLIE RANSOME 
 
 v\ 
 
 WASHINGTON 
 
 GOVERNMENT PRINTING OFFICE 
 
 1904: 
 
i!i RANOROI i i (HRARY 
 
 CONTENTS. 
 
 Page. 
 
 3tter of transmittal 5 
 
 Introduction 7 
 
 Production 8 
 
 Mining and metallurgy 9 
 
 Topography 11 
 
 General geology , 11 
 
 First geological survey of the district 11 
 
 Modifications of earlier results 12 
 
 Economic geology 14 
 
 Earlier work 14 
 
 Extent of productive territory 14 
 
 Underground development 15 
 
 Brief review of the mines 15 
 
 Character of the ores 20 
 
 Structural characteristics of the deposits 22 
 
 Types of deposits 22 
 
 Depth of oxidized zone 26 
 
 Relations of ore bodies to depth 26 
 
 Underground water -_ 31 
 
 Subterranean gases 32 
 
 Future of the district 33 
 
 Index . . 35 
 
LETTER OF TRANSMITTAL. 
 
 DEPARTMENT OF THE INTERIOR, 
 UNITED STATES GEOLOGICAL SURVEY, 
 
 Washington, D. (7., Novembers, 1904. 
 SIR: I have the honor to transmit herewith the manuscript of a pre- 
 liminary report on a "Resurvey of the Cripple Creek district of Colo- 
 rado," by Messrs. Waldemar Lindgren and F. L. Ransoine, under my 
 general supervision. 
 
 Although only ten years had elapsed since a careful study of the 
 geology of this district was made by Messrs. Cross and Penrose, the 
 people of Colorado had been so strongly impressed with the economic 
 importance of a scientific examination of the ground opened by mining 
 operations during that period, that they urgently requested this resur- 
 vey and have materially assisted in its execution. 
 
 The present report, made in advance of the final laboratory exami- 
 nations, is a summary of those facts that bear upon the economic 
 development of the region and are of immediate importance to the 
 miners. I therefore request that it be published with the least possi- 
 ble dela}^ r that its results may be promptly available to all interested 
 in the region. 
 
 Very respectfully, 
 
 S. F. EMMONS, 
 
 Geologist in Charge Section of Metalliferous Deposits. 
 Hon. CHARLES D. WALCOTT, 
 
 Director United States Geological Survey. 
 
REPORT OF PROGRESS IN THE GEOLOGICAL RESURVEY 
 OF THE CRIPPLE CREEK DISTRICT, COLORADO. 
 
 By WALDEMAR LINDGREN and FREDERICK LESLIE RANSOME. 
 
 IKTRODTTCTIOX. 
 
 The Cripple Creek gold deposits were discovered in 1891. Shortly 
 afterwards, in 1894, an examination of the new district was undertaken 
 by the United States Geological Survey, Mr. Whitman Cross having 
 charge of geology and petrography and Mr. R. A. F. Penrose, jr., 
 undertaking the examination of the mines. Their report, accompanied 
 by a geological map, was published in the Sixteenth Annual Report of 
 the Geological Survey, Part II, pages 1-207, and has for the last ten 
 years served as a useful and accurate geological guide to mining 
 operations. 
 
 With the astonishingly rapid development of the Cripple Creek 
 mines the opportunities for geological study multiplied, revealing 
 great complexity of vein phenomena and stimulating a desire for fur- 
 ther investigation, particularly with a view of obtaining some evidence 
 as to the persistence of the veins in depth. This desire found expres- 
 sion in a request by citizens of Colorado for a reexamination of the 
 district by the United States Geological Survey and in an offer of 
 cooperation, whereby the cost would be equally divided between the 
 State of Colorado and the National Survey. The necessary amount 
 having been subscribed in Cripple Creek, Colorado Springs, and Den- 
 ver, the State contribution was put in the hands of Mr. John Welling- 
 ton Finch, State geologist of Colorado, and by him disbursed. The 
 cordial thanks of the geologists in charge of the work are due to Mr. 
 Finch for his hearty and efficient cooperation. 
 
 The reexamination began with a thorough revision of the topographic 
 map of Cripple Creek by Mr. R. T. Evans, Mr. E. M. Douglas in 
 charge. This involved a great deal of painstaking work, nearly every 
 prospect hole being located, as well as all shafts and tunnels. The 
 new map is on the scale of 1:19,495, or about 2i inches to the mile, 
 and includes practically the same area as the old map, a small strip 
 only being added on the western side, so that the total area mapped is 
 about 40 square miles. The small developments outside of this area 
 
 ' 7 
 
RESURVEY OF CEIPPLE CKEEK DISTRICT. [BULL. 254. 
 
 did not seem to justify further extension of the boundaries. Contours 
 are 50 feet apart, and a numbered list of 324 mines is given on the 
 margin of the sheet. A line of accurate levels was run to Cripple 
 Cr6ek from Colorado Springs, thus settling the conflicting data of the 
 different railroads. 
 
 The geological and mining work was undertaken jointly by the 
 authors of this preliminary report. The examination began in June, 
 1903, and, with some interruptions, due to various causes, the field 
 work was concluded in April, 1904. Practically every accessible mine 
 in the district was examined in greater or less detail. Mr. L. C. Gra- 
 ton served as assistant throughout this time, actively participating in 
 all branches of the work. Messrs. A. M. Rock and J. Bruce also 
 rendered very efficient aid as draftsmen. 
 
 PBODTJCTIOK. 
 
 Though situated close to the centers of population in Colorado and 
 in an easily accessible region, the gold deposits of Cripple Creek were 
 not discovered until 1891. To a great extent the lateness of the dis- 
 covery was due to the extremely inconspicuous character of the vein 
 croppings and to the equally inconspicuous appearance of the dark- 
 brown, powdery gold set free by the oxidation of tellurides. As soon 
 as the true character of the veins was ascertained the development of 
 the district proceeded rapidly. In 1894, when the first survey was 
 made, the production was a little less than $3,000,000, but the next 
 year this amount was more than doubled, and in 1900 the maximum 
 production of a little over $18,000,000 was attained. In 1901 and 
 1902 the production declined slowly, and dropped the next year to 
 $13,000,000. The sudden decrease in 1903 was to some extent brought 
 about by the impoverishment of several mines, but the labor troubles 
 of that year had also much to do with it. From August, 1903, to 
 the summer of 1904 many mines experienced more or less difficulty 
 from this cause. It is probable, however, that the output for the 
 current year will show a considerable increase over that of 1903. 
 
LINDGREN AND"] 
 RANSOME. 
 
 PRODUCTION. 9 
 
 Production of the Cripple Creek district according to the reports of the Director of the Mint. 
 
 Year. 
 
 Gold. 
 
 Silver. 
 
 1891 
 
 $449 
 
 Fine dunces. 
 
 1892 
 
 583, 010 
 
 
 1893 
 
 2, 010, 367 
 
 5,019 
 
 1894 
 
 2, 908, 702 
 
 25, 900 
 
 1895 
 
 6, 879, 137 
 
 70, 448 
 
 1896 
 
 7, 512, 911 
 
 60, 864 
 
 1897 
 
 10, 139, 709 
 
 57, 297 
 
 1898 
 
 13, 507, 244 
 
 68, 195 
 
 1899 
 
 - 15,658,254 
 
 82, 520 
 
 1900 
 
 18, 073, 539 
 
 80, 166 
 
 1901 
 
 17, 261, 579 
 
 90, 884 
 
 1902 
 
 16, 912, 783 
 
 62, 690 
 
 1903 
 
 12, 967, 338 
 
 42, 210 
 
 
 
 
 Total 
 
 124, 415, 022 
 
 646, 193 
 
 
 
 
 The total dividends can not be ascertained on account of the many 
 individuals and small companies operating in the district. The divi- 
 dends of the larger companies, it is stated, amounted to $32,752,000 to 
 the end of 1903. In that year it is reported that $1,716,000 was paid 
 by fourteen mines, Portland, Strong, and Stratton's Independence 
 leading, with $360,000, $300,000, and $250,000, respectively. 
 
 MIXING AKB METALLURGY. 
 
 At the present time there are about 300 mines in the district, though 
 many of these are idle and others are consolidated into larger proper- 
 ties. The number of shafts 1,000 feet or more in depth is about 22; 
 of these the Lillie is the deepest, having attained 1,500 feet. Compar- 
 atively few of the mines are pumping, the district being drained by 
 tunnels, as will be described in a following paragraph. The motive 
 power for hoisting is ordinarily steam, electric power being used only 
 in smaller shafts. The mining methods employed present few features 
 of particular interest. The width stoped ranges from 3 to 50 feet or 
 more. The stopes are sometimes filled, but are often left open after 
 the broken rock between levels has been drawn off. Operations are 
 facilitated by the great hardness of the rock, stopes 200 feet or more 
 in height sometimes standing for years. To an annual production of 
 $18,000,000 (1900) corresponded a maximum output of about 600,000 
 tons. The ores are not adapted to concentrating by ordinary means. 
 
 The figures given in the Mint reports are considerably lower than those usually quoted in mining 
 journals and popular descriptions of the district. 
 
10 RESURVEY OF CRIPPLE CREEK DISTRICT. [BULL. 254. 
 
 Hand sorting and washing, the latter in order to separate the fines, are 
 the methods employed. More care is now taken than formerly, but 
 at many places there is still room for improvement. 
 
 The district contains many large mines operated by strong compa- 
 nies, but the system of leasing to individuals and small companies, with 
 royalty charges of 15 to 25 per cent of the net output, remains a 
 conspicuous feature. At the present time the mines of the north- 
 western and northeastern parts of the district are only slightly pro- 
 ductive. Among the formerly highly productive mines in this section 
 may be mentioned the Victor, Isabella, Wild Horse, Damon, Logan, 
 Orpha May, Pharmacist, C. O. D., Gold King, and Anchoria-Leland. 
 The southwest quarter of the district contains the active and impor- 
 tant El Paso, Mary McKinney, and Elkton mines, but the maximum 
 output during the last few years has come from the southeastern por- 
 tion, within which are the Portland, Gold Coin, Ajax, Strong, Golden 
 Cycle, .Vindicator, and Last Dollar mines. The Portland mine has for 
 some time been the heaviest producer in tonnage as well as in value. 
 Its output is from 60,000 to 90,000 tons per annum. In 1903 this 
 mine produced $2,600,000. 
 
 The metallurgical history of the camp is interesting. Beginning 
 with local amalgamating mills, the practice soon changed to local 
 chlorination and cyanide plants. It was soon found, however, that 
 better situations would be found in the valleys, and at present a very 
 large part of the tonnage is shipped to chlorination and cyanide works 
 at Colorado City and Florence. About a sixth of the output, com- 
 prising the higher grade ores, is sent to smelting works at Denver 
 or Pueblo. A still smaller amount is treated in a local chlorination 
 plant near Victor. While in former years the practice leaned more 
 toward the cyanide process, the bulk of the ore is now treated in large 
 chlorination mills with automatic roasters and revolving barrels. It 
 has always been found necessary to roast all except the completely 
 oxidized ores. At the present time there are in the district two small 
 mills in which the cyanide process is used without previous roasting, 
 and which are thus enabled to work ores containing as little as $5 a 
 ton in gold. The extent of these low-grade ores is not yet fully 
 demonstrated. Regarding the value of the ore, see page 21. 
 
 Treatment charges at the mills fluctuate somewhat, but usually range 
 from $7 to $13 a ton, according to the tenor of the ore; in the early 
 part of 1904 the prices were reduced, it is reported, and ranged from 
 $5. 50 to $10 per ton. Recently they have again been increased. On the 
 whole the mining and milling expenses are very high at Cripple Creek 
 compared with those of other localities western Australia, for exam- 
 ple, where similar ores and conditions prevail. Few of the large 
 mines seem to have reduced total expenses below $16 per ton. 
 
TOPOGRAPHY AND GENERAL GEOLOGY. 11 
 
 RANSOME. 
 
 TOPOGRAPHY. 
 
 The mines are situated in a group of bare, rounded hills forming 
 part of the high plateau extending south westward from Pikes Peak, and 
 are only about 10 miles distant from that prominent landmark. The 
 elevations range from 9,000 to nearly 11,000 feet above sea, the highest 
 point in the district being Trachyte Mountain (10,863 feet). Bull 
 Hill and Bull Cliff are but slightly lower. The drainage is chiefly 
 southward toward the Arkansas River. The district contains two 
 important towns. Cripple Creek is situated on the northwest side of 
 the producing area, while Victor, 3 miles distant, lies on the south- 
 west edge of the same area. Two railroads connect the district with 
 Colorado Springs, the Colorado Midland circling around the north 
 side of Pikes Peak, while the Short Line descends to the valley along 
 the picturesque eastern slope of the same mountain. The Florence and 
 Cripple Creek Railroad runs southward to Florence in the Arkansas 
 Valley. An excellent system of electric-car lines connects the towns 
 with all the important mines. 
 
 GENERAL GEOLOGY. 
 
 FIRST GEOLOGICAL SURVEY OF THE DISTRICT. 
 
 When Mr. Whitman Cross made his careful study of the geology of 
 the Cripple Creek district, ten years ago, mining had barely begun 
 and the various hills were not, as now, perforated by deep under- 
 ground workings. That his work has in general stood the test of 
 subsequent underground exploration and continues to be highly 
 regarded in the district is convincing proof of its high quality. . Later 
 workers, however they may modify or amplify his results, should 
 acknowledge their debt to the pioneer who first deciphered the 
 history of this volcanic district. The account of general geology, as 
 given by Cross, ma} 7 be very briefly summarized as follows: 
 
 The Cripple Creek hills lie near the eastern border of an elevated 
 and much dissected plateau which slopes gently westward for 40 
 miles, from the southern end of the Colorado Range, dominated by 
 Pikes Peak, to the relatively low hills connecting the Mosquito and 
 Sangre de Cristo ranges. The prevailing rocks of this plateau are 
 granites, gneisses, and schists. The granites inclose masses of Algon- 
 kian quartzite and are therefore post-Archean. But they are older 
 than the only Cambrian sediments known in Colorado, and on the 
 Cripple Creek map have been indicated as Algonkian. During 
 Tertiary time volcanic eruptions broke through these ancient rocks at 
 several points and piled tuffs, breccias, and lavas upon the uneven 
 surface of the plateau. The eruptive rocks of the Cripple Creek 
 district are the products of one of the smaller isolated volcanic centers 
 
12 RESURVEY OF CRIPPLE CREEK DISTRICT. [BULL. 254. 
 
 of this period, a center characterized by the eruption of phonolite, 
 which does not occur elsewhere in this general region. 
 
 The most voluminous products of the Cripple Creek volcano now 
 preserved are tuffs and breccias. They occupy a rudely elliptical 
 area in the center of the district, about 5 miles long in a northwest- 
 southeast direction and about 3 miles wide. According to Cross these 
 breccias and tuffs rest in part upon an earlier flow of andesite, but 
 mainly upon an unevenly eroded surface of the granites and schists, 
 although along the southwest edge of the area the contact was found 
 to be so steep as u to support the idea that the central vent or vents of 
 the volcano were adjacent to this line." The breccia is much indurated 
 and altered, but was thought by Cross to consist mainly of andesitic 
 fragments, although it was recognized that fragments of phonolite are 
 locally abundant. The most characteristic massive rock of the Cripple 
 Creek volcano is phonolite, which was erupted at several periods and 
 more abundantly than any other type. It occurs as dikes and masses, 
 not only in the breccia but in the surrounding granitic rocks. 
 
 The general succession of igneous rocks, according to Cross, is as 
 follows: The earliest rocks were andesites containing some orthoclase. 
 Then came a series of allied phonolitic rocks, rich in alkalies and mod- 
 erately rich in silica, together with some andesites. Among them are 
 trachytic phonolite, nepheline-syenite, syenite-porphyry, phonolite, 
 mica-andesite, and pyroxene-andesite. Phonolite was erupted at sev- 
 eral periods. The nepheline-syenite he considered as probably younger 
 than the trachytic phonolite. At the close were intruded a small num- 
 ber of narrow dikes of basic rocks, the so-called basalts, which contrast 
 very markedly with the phonolite. 
 
 MODIFICATIONS OF EARLIER RESULTS. 
 
 In the course of the present investigation the geology of the 
 district has been entirely remapped upon the carefully revised topo- 
 graphic base. The granites, gneisses, and schists have been differen- 
 tiated and outlined in greater detail than was practicable in the earlier 
 investigation. The oldest rocks in the district are muscovite- and 
 fibrolite-schists. These are closely associated with the fine-grained 
 granitic gneisses such as underlie most of the town of Cripple Creek. 
 This gneiss, in the earlier report, was mapped partly as schist and 
 partly as granite. Both gneiss and schist are cut by a reddish granite 
 which occupies a considerable area extending from Anaconda west- 
 ward beyond the limits of the area studied. This granite is well 
 exposed along Cripple Creek in the vicinity of Mound. 
 
 A second type of granite distinguished and mapped is the coarsely 
 porphyritic rock referred to by Cross as the Pikes Peak type of granite. 
 This rock occupies over half of the district and is the prevailing type 
 
LINDGREN AND 
 BANSOME. 
 
 ] GENERAL GEOLOGY. 13 
 
 along the northern, eastern, and southern borders of tut, area. It is 
 well exposed on Squaw Mountain and is the granite of the El Paso, 
 Elkton, Ajax, Portland, Independence, and Gold Coin mines. Of 
 these two kinds of granite the Cripple Creek variety is probably the 
 younger. The Cripple Creek gianite, the gneiss, and the schist 
 together form a wedge-shaped area projecting into the Pikes Peak 
 granite from the west. The center of volcanic disturbance practically 
 coincides with the point of this wedge. 
 
 The present investigation indicates some necessary modifications of 
 the earlier report in the way- of stronger emphasis on the intimate 
 genetic relationship of the rocks. The "phonolite," "nepheline x - 
 syenite," "trachytic phonolite," "syenite-porphyry," and "andesites" 
 of Cross are all very closely related and have been found to be in most 
 cases connected by intermediate types. They are clearly all slightly 
 divergent eruptive facies of one general magma characterized chemi- 
 cally by containing from 9 to 15 per cent of potash and soda, the soda 
 being always somewhat higher than the potash, particularly when the 
 comparison is made by molecular ratios. None of the massive rocks 
 can properly be called andesite, and although it can not be affirmed 
 that andesitic fragments are entirely absent from the usually much 
 altered volcanic breccia, the term "andesitic breccia" does not seem 
 applicable to this formation as a whole. It would be more accurate to 
 describe it as a phonolitic breccia, although in places it consists chiefly 
 of particles of the older rocks through which the Tertiary eruptives 
 broke. 
 
 None of the massive rocks erupted from the Cripple Creek volcanic 
 center and now preserved in the district show any evidence of having 
 been surface flows. They are for the most part intrusive porphyries, 
 ranging in texture, however, from the granular so-called nepheline- 
 syenite near the town of Independence to the nearly aphanitic phono- 
 lite of the smaller dikes and sheets. Most of them will come under 
 the designations phonolite, trachytic phonolite, trachydolerite, and 
 alkali-syenite. The extensive underground workings show that the 
 " nepheline-syenite " does not cut the "trachytic phonolite," but that 
 the two rocks represent textural and, to some extent, mineralogical 
 facies of the same mass, while the trachytic phonolite in turn may pass 
 into phonolite. The trachytic phonolite is in some instances cut by. 
 dikes of phonolite, showing, as Cross has already pointed out, that the 
 phonolitic intrusions were not all synchronous. 
 
 While it is undoubtedly true that much of the breccia in the north- 
 eastern part of the volcanic area rests upon a very uneven surface of 
 granite, gneiss, and schist, the results of field work during the last 
 season, favored by deep workings not in existence when the district 
 was originally surveyed, have emphasized the fact that the breccia 
 lying southwest of a general northwest-southeast line drawn through 
 
14 RESCTRVEY OF CRIPPLE CREEK DISTRICT. [BULL. 254. 
 
 Big Bull Mountain and Gold Hill occupies a chasm of profound depth 
 in the fundamental rocks of the region. From the Conundrum mine 
 on the western slope of Gold Hill to Stratton's Independence mine on 
 the south slope of Battle Mountain the contact plunges steeply down, 
 with dips ranging in general from 70 to vertical. In some instances 
 the granite walls of this chasm actually overhang the breccia. It is 
 probable that this entire southwest contact represents a part of the 
 wall of the great pit formed by the volcanic explosions that produced 
 the breccia. It is further probable that an arm or branch of this 
 volcanic abyss, now filled with breccia and intrusive rocks, extends 
 northeastward past Bull Cliff and the town of Altman. 
 
 ECONOMIC GEOLOGY. 
 
 EARLIER WORK. 
 
 To the excellent work of Mr. R. A. F. Penrose, jr., apply statements 
 similar to those made in the discussion of the purely geological branch 
 of the subject. Few shafts had then attained a depth of 400 feet, and 
 most of the exposures were masked by surface oxidation. It would 
 be surprising, in view of the facilities created by the later develop- 
 ment of hundreds of mines, if a subsequent investigation should not 
 bring out some slight modifications of earlier results. 
 
 EXTENT OF PRODUCTIVE TERRITORY. 
 
 There is nothing in the history of the district since 1894 warranting 
 any extension of the bounds of the productive territory as then known. 
 Now, as then, a circle of 3 miles radius described from the summit of 
 Gold Hill would include all deposits of known or prospective value, 
 while the really important mines would be embraced by a circle of about 
 half that radius, with its center near the summit of Raven Hill. That 
 scattered deposits of greater or less value may be found in outlying 
 portions of the district is by no means improbable. But the close 
 dependence of the typical Cripple Creek ores upon the main volcanic 
 center, and the consequent remarkable compactness of the gold-bearing 
 area, are features highly characteristic of the district and are likely 
 always to remain so. 
 
 The greater part of the ore has undoubtedly come from the central 
 area of breccia, particularly from that part of this area in which the 
 breccia extends to great depth. Very productive ore bodies have 
 been found, however, in the granitic rocks, usually within 1,000 feet 
 of the steep contact limiting the breccia on the southwest. The im- 
 portant Beacon Hill mines, with ore bodies nearly three-quarters of a 
 mile from this contact, are exceptional, and are probably genetically 
 connected with the intrusive mass of phonolite forming the core of 
 the hill. 
 
ECONOMIC GEOLOGY. 15 
 
 UNDERGROUND DEVELOPMENT. 
 
 At the time of the earlier survey the deepest shafts, those of the 
 Moose, Pharmacist, and Anna Lee mines, were down only about 400 
 feet, while few of the other mines were over 200 feet in depth. Many 
 subsequently prominent mines were then mere prospects or had not 
 been located. 
 
 The deepest shaft at present is the Lillie, which is over 1,500 feet 
 deep, although the Stratton's Independence shaft, 1,400 feet deep, has 
 the lowest sump in the district. The American Eagle shaft is nearly 
 as deep as the Lillie, while there are about twenty other shafts over 
 1,000 feet in depth, and at least 100 shafts deeper than the deepest 
 workings existing in 1894. As regards absolute elevations, the Gold 
 Hill shafts are scarcely down to a level of 9,000 feet above sea; the 
 Elkton, El Paso, and Lillie shafts descend to 8,750 feet; Stratton's 
 Independence reaches the lowest level at 8,450 feet; while the Gold 
 Coin shaft, at 8,550 feet, is of interest from the fact that the deepest 
 ore shoot in the district is now being stoped from its twelfth level. 
 
 The amount of drifting and crosscutting accomplished since the 
 earlier survey is more than commensurate with the increased number 
 and depth of the shafts, and the district is further intersected in vari- 
 ous directions and at different levels by two long tunnels run for 
 drainage purposes and by a dozen or more extensive adits, many of 
 which have their portals in the granitic rocks and extend well into the 
 central part of the breccia area. 
 
 BRIEF REVIEW OF THE MINES. 
 
 The productive district, as stated above, is practically covered by the 
 area of a circle 3i miles in diameter. The center of this circle would be 
 located halfway between Raven Hill and Bull Hill, and the towns of 
 Cripple Creek, Victor, and Cameron would be situated on its peripheiy . 
 A very few mines notably the Galena and the Fluorine and many 
 prospects lie outside of this area. 
 
 The culminating points of the district are found in a ridge of higji 
 and bare hills that extends in a northwest-southeast direction and 
 divides the waters flowing into Cripple Creek and Wilson Creek on the 
 southwest from those joining Spring Creek and Grassy Creek on the 
 north. From northwest to southeast the following hills mark this 
 divide: Mineral Hill, Carbonate Hill, and Tenderfoot Hill, north 
 or northeast of Cripple Creek; Globe Hill, Ironclad Hill, and Bull 
 Hill, the latter being near the center of the district and equidistant 
 from Cripple Creek and Victor; the ridge is continued by Bull Cliff 
 and Big Bull Mountain, the latter, really outside of the productive 
 area, being the highest point in this dividing range of hills. Its ele- 
 vation is 10,826 feet. Three long spurs project to the southwest from 
 
16 RESURVEY OF CRIPPLE CREEK DISTRICT. [BULL. 254. 
 
 the dividing range separating the deep trenches of Cripple Creek, 
 Squaw Gulch, Arequa Gulch, and Wilson Creek; the first, called Gold 
 Hill, rises directly east of Cripple Creek; the second is Raven Hill, 
 being continued to the southwest by the lower spur of Guyot and 
 Beacon hills; the third is Battle Mountain, continued by the almost 
 equally high salient of Squaw Mountain. 
 
 The important mines are situated in this region of sharply accentu- 
 ated topography. As has been several times emphasized, the volcanic 
 area practically coincides with the hills and ridges just described and 
 is surrounded on all sides by granitic rocks. 
 
 Globe and Ironclad hills and Gold and Raven hills consist chiefly of 
 heavy masses of breccia, and were scenes of great activity during the 
 early years of the district. Near Poverty Gulch, just northeast of 
 Cripple Creek, is the Abe Lincoln, not a large mine, but still actively 
 worked with satisfactory results. Higher up are the Gold King, with 
 dividend records of $150,000, and the C. O. D., with a reported pro- 
 duction of $600,000 and dividends of $150,000. Both were idle in 1904 
 and have attained their eighth or ninth levels. 
 
 On the summit of Globe Hill are the Stratton properties of Ply- 
 mouth Rock and Globe mines, in which extensive low-grade mineraliza- 
 tion without many sharply defined veins seems to be the rule. 
 Adjoining is the property of the Homestake Company, including the 
 Ironclad mine, where direct cyaniding of oxidized surface ores is now 
 carried on in a mill erected on the property. 
 
 Gold Hill is crowned by the Anchoria-Leland mine, with a produc- 
 tion of over $1,000,000 and dividends of $198,000. The shaft is 1,100 
 feet deep. The adjoining Moon- Anchor has paid dividends of $261,000, 
 and the Half Moon (Matoa G. M. Co.) has a gross production of $650,000 
 to its credit, but is reported to have paid only a small amount in divi- 
 dends. None of these mines is being worked at present, except on a 
 small scale by lessees. 
 
 On the western slope is the Midget mine, actively worked at present, 
 with a depth of 800 feet, a total production of $662,000, and dividends 
 of $195,000. The Conundrum, in the same vicinity, is likewise worked 
 with good results to a depth of 600 feet. The Midget, like the mines 
 described above, follows a vein in breccia, while the Conundrum is min- 
 ing on a "basalt" dike in granite, close to the contact of the breccia. 
 
 In the deep gulch between Gold Hill and Raven Hill are situated 
 the Anaconda, Doctor-Jack Pot, and Mary McKinney mines, all work- 
 ing on sheeted zones forming lodes in the breccia. The Anaconda pro- 
 duced about $1,000,000, chiefly from upper levels, and is now idle. 
 The Mary McKinney is one of the most successful mines worked at 
 present in the district. Its depth is 600 feet. The Doctor-Jack Pot 
 has $4,000,000 to its credit and likewise a handsome dividend record. 
 
] THE MINES. 17 
 
 The shaft is only 700 feet deep, water having until now prohibited 
 deeper sinking. 
 
 The breccia-granite contact is found on Guyot Hill a short distance 
 south of the Mary McKinney. The extreme spur of Raven Hill, 
 called Beacon Hill, is formed of an intrusion of phonolite in granite, 
 and about this outlying volcanic center cluster a group of veins of 
 great production and promise. On the eastern side of the hill are 
 located the Prince Albert, Gold Dollar, and others, not active pro- 
 ducers at present, while on the western side lie the El Paso, C. K. 
 & K, and Old Gold mines, with their narrow but extremely rich fis- 
 sure veins in granite, now actively and successfully worked. 
 
 A great number of smaller mines have been worked on veins cut- 
 ting the breccia of Raven Hill. The famous Elkton mine is situated in 
 the deep hollow between Raven Hill and Battle Mountain. It has been 
 working on an exceptionally long vein, partly contained in breccia, 
 partly in granite, and generally following a ' 'basalt" dike. The produc- 
 tion approaches $6,000,000, and the depth attained is about 900 feet, 
 excessive water having formed a serious obstacle to deeper sinking. 
 Dividends amount to $1,200,000. The Moose mine, situated higher 
 up on the slope of Raven Hill, had a good ore shoot, from which 
 $500,000 was obtained. 
 
 Continuing northwest, we soon attain the summit of Bull Hill, which 
 affords a magnificent panorama, not only of the whole camp, but of 
 a large part of the State of Colorado. Toward the east, and 5,000 feet 
 lower, spread the great plains at the foot of the Rocky Mountains; 
 westward the Sangre de Cristo, Collegiate, and Mosquito ranges a 
 snowy and jagged line of ramparts define the distant horizon. 
 
 A multitude of small mines occupy the southwestern slope of Bull 
 Hill. On the northwestern side an area of brecciated granite appears 
 among the volcanic rocks, and in this formation is situated the Wild 
 Horse mine. This lode, which has been worked to a depth of 1,250 
 feet, has produced over $1,000,000, but is now operated only by 
 lessees. A number of smaller producers may be found on the north- 
 ern slope, toward Cameron, among them the Damon, Jerry Johnson, 
 W. P. H., and Pinnacle. 
 
 Those who have followed this description on a map will have noticed 
 that the mines are chiefly situated on the periphery of a circular area, 
 the central part of which, comprising the upper part of Squaw Gulch, 
 has thus far yielded very little. Few strong veins have been met 
 with in this part of the breccia, but, on the other hand, the devel- 
 opments in depth are not extensive. 
 
 On the east and southeast side of Bull Hill begins that most impor- 
 tant belt of lodes which extends southward to Victor and includes the 
 richest group of producers in the camp. A characteristic feature of 
 Bull. 25405 2 
 
18 RESURVEY OF CRIPPLE CREEK DISTRICT, [BULL. 254. 
 
 this belt is the intrusion into the breccia of thick masses of trachytic 
 phonolite and syenitic rocks. 
 
 With few exceptions the veins of this belt strike north-northwest. 
 We may begin the description with the system of linked veins, 3,000 
 feet long, covered by the Isabella and Victor mines. The last-named 
 mine, on the southern end of the system, is situated just below the 
 western slope of Bull Cliff. It has been worked to a depth of over 
 1,000 feet, has produced about $2,200,000, and has paid dividends 
 amounting to $1.150,000. The Isabella has attained a depth of 1,127 
 feet, produced $3,200,000, and paid dividends of $600,000. Both mines 
 lost their pay shoot in depth. 
 
 The small but rich cross veins of the Empire State, Burns, 
 Pharmacist, and Zenobia connect this vein system with that of the 
 Stratton mines on Bull Hill. South of the Burns begins the great 
 Vindicator vein system, traced southeasterly for a mile through the 
 Findley, Hull City, Vindicator, Lillie, and Golden Cycle mines. The 
 Hull City and the Lillie have each produced over $1,000,000, the Vin- 
 dicator and Golden Cycle over $2,000,000 each, all with correspond- 
 ing dividend records. The Lillie is deepest, having attained 1,500 feet. 
 Next in depth is the Vindicator, 1,200 feet. All of them, except the 
 Lillie, are still actively worked. In the whole system water has been 
 and is still a source of trouble. The deepest mine evidently drains 
 all the others in this vicinity. 
 
 The Stratton properties on Bull Hill, with the Logan, Orpha May, 
 and Pikes Peak veins, on which maximum depths of 1,200 and 1,500 
 feet have been attained, are now worked only to a slight extent, 
 whereas in the early days of the camp they were highly productive. 
 
 This vein system is continued southward in the Last Dollar mine, 
 now working at a depth of 1,270 feet. The production exceeds 
 $1,000,000. South of the Last Dollar the veins enter the Modoc 
 ground, a mine worked for a long time and with gratifying success. 
 The Blue Bird, an old-time producer, is situated a short distance west 
 of the Last Dollar. 
 
 South of the Modoc is the Battle Mountain vein system, crossing 
 from the granite into the breccia, with general northerly or north- 
 northwesterly directions, and distinguished by heavy production 
 and ore bodies of imposing size. None of the veins are of great 
 length, and the whole system extends scarcely a mile along the strike 
 of the veins. The veins can not be directly connected with others 
 already described, though, in its general trend, the system heads 
 toward the Dexter, Blue Bird, and Moose veins. 
 
 Beginning on the southwestern side, we first come to the Gold Coin 
 mine, the veins of which are in granite; one of them is successfully 
 worked at present at a depth of 1,200 feet. The total production 
 approaches $6,000,000; the dividends paid exceed $1,000,000. North 
 
LINOGREN AND~| rivcr^ T\lT-\n?Q 1 Q 
 
 RANSOME. J THE MINES. iy 
 
 of the Gold Coin is the Ajax, working partly in veins, partly in large, 
 irregular ore bodies in the granite. The total production is very con- 
 siderable. The depth attained is 1,200 feet. 
 
 Between this and the Portland vein system, almost within the town 
 of 'Victor, are the Granite, Dillon, and Dead Pine veins. They are 
 worked at present at depths of from 800 to 1,000 feet. 
 
 The Portland vein system begins on the south at the Strong mine, 
 now worked at a maximum depth of 900 feet, on a vein in granite 
 that follows a " basalt" dike, which is in places accompanied by a 
 phonolite dike. The mine is an unusually regular and profitable 
 producer, the total dividends since 1892 amounting to $2,500,000. 
 
 The veins of Stratton's Independence run about parallel to those of 
 the Strong, a few hundred feet eastward. They extend from the 
 granite into the breccia, following for some distance a phonolite dike. 
 The production of this mine amounts to over $11,000,000, with a divi- 
 dend record of $4,000,000 since 1899. At present the company is 
 leasing the various levels to tributers. From the two properties last 
 described the vein systems continue into the Portland mine, but in 
 the northern part of that great property are replaced by another and 
 still richer aggregate of veins, the Captain system. The Portland is, 
 beyond question, the most prominent mine of the Cripple Creek dis- 
 trict. Its total production from 1894 to the end of 1903 amounted to 
 $18,000,000, derived from 466,000 tons of ore (both in round figures), 
 from which $4,600,000 has been paid in dividends, the remainder going 
 to acquirement of territory, extensive milling and mining plants, and 
 operating expenses. 
 
 Outside mining properties. The area outside of the principal vol- 
 canic area contains very few productive properties, but it is by no 
 means barren. A great deal of money has been spent here, usualty 
 with unsatisfactory results. Although there are many properties of 
 merit and although much honest effort has been made in this part of 
 the district^ it has long been the favorite camping ground of concerns 
 more or less lacking in stability. 
 
 The granite hills west and south of the city of Cripple Creek con- 
 tain few prospects; phonolite dikes occur in places, but usually show 
 little value. Along Gold Run and Arequa Gulch prospects with a little 
 ore have been found, down to the junction with Cripple Creek, and 
 even at isolated places below this locality. Grouse Mountain, with its 
 phonolite cap, shows many prospects from which occasional good assays 
 have been obtained, but neither here nor on Straub and Brind moun- 
 tains has anything of permanent value been developed thus far. It is 
 claimed that ore bodies of low grade, containing a few dollars per ton, 
 exist. 
 
 The breccia caps of Mineral, Carbonate, and Tenderfoot hills are 
 dotted with prospect dumps, and even shafts several hundred feet 
 
20 RESURVEY OF CRIPPLE CREEK DISTRICT. [BULL. 254. 
 
 deep. Nothing of permanent value is recorded from Mineral Hill, 
 though fairly productive placers have been worked at its southwestern 
 base, almost in the town of Cripple Creek. 
 
 On Carbonate Hill the Elkhorn has been a small producer; on Ten- 
 derfoot Hill the Friday, Hoosier, Black Diamond, and Mollie Kathleen 
 contribute their parts to the production. Two miles north-northwest of 
 Cripple Creek is the Galena mine, the vein of which follows, for a part 
 of its course, a phonolite dike in granite and has a small output to its 
 credit. About the same distance north of the city is the small volcanic 
 center of Copper and Rhyolite mountains. At the former the Fluorine 
 mine has produced $160,000, and low-grade ore is now being cyanided. 
 Prospects are found on Rhyolite Mountain, and in fact all over the flat 
 granite country between it and Trachyte Mountain. The Lincoln mine, 
 near Gillette, and several other prospects farther south, along a belt 
 of phonolite dikes, have produced a little ore. It is claimed that there 
 are low-grade veins on both sides of Bernard Creek, northwest of 
 Gillette, in a region of granite with occasional dikes and masses of 
 phonolite. Trachyte Mountain, southeast of Gillette, is covered by 
 phonolite, and a little ore is occasionally found in veins at its southern 
 foot. Some work has also been done on Cow Mountain, about 4 miles 
 northeast of Bull Hill. 
 
 The eastern margin of the central volcanic area, east of Victor Pass 
 and extending southward across Big Bull Mountain to Brind Mountain, 
 has thus far failed to produce anything of importance, though well 
 covered by prospects. A survey of 'these outlying parts of the district 
 serves to emphasize strongly the remarkable concentration of deposits 
 within the narrow limits of the central volcanic area. 
 
 CHARACTER OF THE ORES. 
 
 The characteristic feature of the Cripple Creek ores is the occurrence 
 of the gold in combination with tellurium, chiefly as calaverite, but 
 partly also as the more argentiferous sylvanite, 05 and probably to a 
 minor extent as other gold, silver, and lead tellurides. The tellurides 
 are frequently associated with auriferous and highly argentiferous 
 tetrahedrite, with molybdenite, and occasionally with stibnite. While 
 these minerals have not yet been closely studied, preliminary examina- 
 tion indicates that their contents in gold are due to an intimate mechan- 
 ical mixture of tellurides. Pyrite, while widely disseminated through 
 the country rock and of common occurrence in the fissures, is rarely 
 sufficiently auriferous to constitute ore. Such of the pyritic ores as 
 have been tested reveal the presence of tellurium, indicating that the 
 ore is a mixture of pyrite and gold-silver tellurides. Galena and 
 
 a Calaverite ( AuAg) Te2: tellurium, 57.4 per cent; gold, 39.5 per cent; silver, 3.1 per cent. Sylvanitc 
 (AuAg) Te 2 : tellurium, 62.1 per cent; gold, 24.5 per cent; silver, 13.4 per cent. 
 
L1N B D ANsoME. ND ] CHARACTER OF THE ORES. 21 
 
 sphalerite occur in small quantities in many of the mines, but rarely 
 contain enough of the precious metals to form ore. Native gold 
 appears to be absent from the telluride ores, except as it may be set 
 free by the oxidation of these tellurides. 
 
 The usual gangue minerals of the ores are quartz, fluorite, and dolo- 
 mite. Roscoelite and rhodochrosite are also found in places. Celestite, 
 or sulphate of strontium, while never present in large amount, fre- 
 quently occurs as little acicular crystals in the quartz vugs of the lodes. 
 Calcite occurs interstitially in much of the breccia near the ore bodies, 
 but is rarely found in distinct crystalline form with the ore minerals. 
 Secondary potassium feldspar is common in the ores; it is especially 
 abundant in the ores inclosed in granite, particularly those in the 
 Pikes Peak type. This feldspar has the composition of orthoclase or 
 microcline, and is formed by the rec^stallization of the original 
 potassic feldspar contained in the rocks. In the granitic ores of the 
 Stratton's Independence, Portland, Ajax, and Elkton mines, this sec- 
 ondary feldspar is the principal gangue mineral. 
 
 Oxidized ores, while still worked in many properties, are of rela- 
 tively less importance than when Penrose described the district. 
 They contain the characteristic dull gold, often in pseudomorphous 
 skeletons, resulting from the oxidation of the tellurides, associated 
 with tellurite (tellurium dioxide), emmonsite or durdenite (both 
 hydrated ferric tellurites), and probably other oxidized compounds of 
 tellurium and iron. These minerals occur in association with kaolin, 
 alunite, and ferruginous clays. The deep workings of the present 
 day show that kaolin is always connected with oxidation, and is not a 
 product of the original mineralization of the district, as was supposed 
 by Penrose. 
 
 The Cripple Creek ores, as a rule, contain very little silver, the 
 average proportion being about 1 ounce of silver to 10 ounces of gold. 
 In the Portland and Stratton's Independence mines the proportion is 
 very much less, the silver from the Portland in 1901 amounting to 
 only 2.4 ounces for each 100 ounces of gold. In the Blue Bird, 
 Doctor-Jack Pot, Conundrum, Pointer, and other mines containing 
 notable amounts of tetrahedrite or galena, the proportion of silver 
 rises considerably above the average. 
 
 The average value of the Cripple Creek ores lies probably between 
 $30 and $40 per ton. In some of the larger mines the average value 
 sinks to about $25 per ton. From a lower economic limit of about 
 $12 per ton the values of individual shipments swing through a wide 
 range up to ores carrying $3,000 or $4,000, or even $8,000, per ton. 
 Occasionally smaller amounts one or two tons have yielded as much 
 as $50,000 per ton. 
 
22 RESURVEY OF CRIPPLE CREEK DISTRICT. [BULL. 254. 
 
 STRUCTURAL CHARACTER OF DEPOSITS. 
 
 With few exceptions the ore bodies, of whatever shape, are causally 
 connected with fissures, and most of them constitute fissure veins of 
 various types. The fissure system of the district appears to radiate 
 from a point near the northern limit of the volcanic area. In the 
 eastern part the prevailing directions are northwest or north-northwest, 
 gradually changing to a northerly strike in the southern portion and 
 to predominant north-northeast or northeast courses in the western 
 side of the district. 
 
 Individual veins are rarely over half a mile in length, but linked- 
 vein systems often extend for a mile in the same direction. The dip 
 is generally veiy steep. The movement along these fissure planes 
 appears in all cases to have been very slight. The fissures charged 
 with ore are sometimes simple veins with one fracture plane; much 
 more commonly, however, they are composite veins or lodes which 
 consist of several closely spaced and frequently linked fissures, all 
 more or less ore bearing. A better expression for this structural type 
 as it appears in Cripple Creek is the term " sheeted zone." 
 
 TYPES OF DEPOSITS. 
 
 The most important types of auriferous ore bodies occurring in the 
 district are: 
 
 1. Tabular in form and strictly following simple fissures or sheeted 
 zones. A subtype comprises lodes in which the sheeted zone follows 
 "basalt" or phonolite dikes. 
 
 2. Irregular bodies adjacent to fissures and formed by replacement 
 and recrystallization of the country rock usually granite. 
 
 These types are not always sharply distinct, but may be connected 
 by deposits of intermediate character. 
 
 All the ore bodies, of whatever type, exhibit certain common features 
 which serve to distinguish the deposits of Cripple Creek from those 
 of most other mining districts. In the first place, the actual openings 
 in the rocks available for the deposition of ore are, as a rule, remark- 
 ably narrow. In the second place, the amount of material carried in 
 the mineralizing solutions and deposited as gangue and ore minerals 
 was comparatively small. In consequence of these two conditions, the 
 district contains no such massive veins, solidly filled with quartz or 
 other vein minerals, as are characteristic of the San Juan region in 
 Colorado or the Mother Lode region in California. Even the small 
 fissures of the Cripple Creek district are rarely completely filled, but 
 exhibit a characteristic open or vuggy structure. Where the fractures 
 are of unusual width, or where the i jcks are extensively shattered, as 
 in the Midget and Moose mines, the small volume of available vein 
 matter is particularly noticeable. The walls of such fractures and the 
 
] TYPES OF DEPOSITS. 23 
 
 fragments of the shattered rock are usually merely coated with a thin 
 deposit of quartz, fluorite, and other minerals. As the rich tellurides 
 were usually among the minerals last to form, and are particularly 
 abundant on the walls of the vugs, it is probable that had quartz, fluor- 
 ite, or other gangue minerals been more abundantly deposited the 
 ores would have been of much lower grade. 
 
 Sheeted veins. The mineralized sheeted zones constitute the most 
 characteristic deposits of the district and occur in practically all the 
 rocks, although particularly common in breccia. They consist of a 
 varying number of narrow, approximately parallel fissures, together 
 composing a sheeted zone that may range from a fraction of a foot to 
 50 or 60 feet in width. Such uncommonly wide zones of fissuring, 
 however, can usually be resolved into two or more sheeted zones lying 
 so close together that the whole constitutes for practical purposes a 
 single ore body, as in the Captain vein system of the Portland mine. 
 Usually the sheeted zones are from 2 to 10 feet in width. In other 
 cases the fissures may be very numerous, the rock for a foot or more 
 in width being divided into thin parallel slabs, while on each side of 
 this medial portion the fissures become farther and farther apart as 
 the lode grades into the normal country rock of the vicinity. In still 
 other cases there may be two main fissures, 3 or 4 feet apart, accom- 
 panied b}^ more or less irregular fracturing of the intervening and 
 adjacent rock. As a rule the fissures are mere cracks, showing no 
 brecciation, slickensiding, or other evidence of tangential movement 
 of the walls. Usually the tellurides are exclusively confined to the 
 narrow fissures and cracks, and do not, in this type of deposit, in any 
 sense constitute a replacement of the country rock. The rocks in the 
 vicinity of the fissures are partly replaced by dolomite, pyrite, and 
 a little fluorite; the telluride ores, however, do not share this pro- 
 pensity, but coat the open fissures, associated with a little quartz and 
 fluorite. Replacement by tellurides does occur in two other types of 
 deposits, to be described later; but as regards the simple veins and 
 sheeted zones, it will be necessary to modify the results of Penrose by 
 restricting the metasomatic role of the tellurides. In the oxidized 
 parts of the veins, such as were almost exclusively available for obser- 
 vation when Penrose visited the district, these relations can seldom be 
 clearly ascertained, and would easily lead one to overemphasize replace- 
 ment as a feature of vein formation. The fissures are not, in general, 
 planes of faulting. Appreciable movement has undoubtedly occurred 
 in some instances, but the displacement probably rarely exceeded 1 or 
 2 feet. 
 
 Although found most abundantly in the breccia or trachytic phono- 
 lite, sheeted zones and single fissures are often well developed in the 
 granite, as in the El Paso, C. K. & N., and Gold Coin mines. While in 
 some of these lodes the ore minerals are as plainly confined to the fis- 
 
24 BESUKVEY OF CRIPPLE CREEK DISTRICT. [BULL. 254. 
 
 sures as in the breccia, in other cases the ore to some extent permeates 
 the granite alongside the fissure, this constituting a deposit interme- 
 diate in nature between types 1 and 2. They also frequently follow 
 phonolite dikes, the general tendency of these dikes to develop a platy 
 parting parallel to their walls being particularly favorable to the produc- 
 tion of a well-defined sheeted zone when the direction of fissuring hap- 
 pens to coincide with that of the dike. 
 
 The metasomatic alteration accompanying these sheeted zones is sur- 
 prisingly slight, and consists of a partial replacement of the breccia, 
 phonolite, trachytic phonolite, or "basalt" by dolomite and pyrite 
 accompanied by a small amount of sericite and a little secondary potash 
 feldspar. But even in the most altered rock the newly formed min- 
 erals rarely form more than a small percentage of the rock mass. The 
 alteration in granite exhibits a somewhat different phase, described in 
 a subsequent paragraph. 
 
 Not all the sheeted zones carry ore, nor is the ore of a productive 
 sheeted zone necessarily coextensive with the fissuring. The ore occurs 
 in pay shoots up to 2,000 feet in length and 1,000 feet in depth, but 
 usually very much smaller than is indicated by these limits. The 
 boundary between the ore and the barren portions of the lode can be 
 determined, as a rule, only by assays. No single factor that can 
 account for the localization of the ore in these pay shoots has been 
 discovered. In some mines the pay shoots occur where the lode is 
 intersected by cross fissures; in other mines no such relation exists. 
 In some mines ore occurs where the fissures pass through phonolite 
 dikes; in other mines the lode, elsewhere productive, becomes barren 
 when it enters phonolite; while in still others the presence of the 
 phonolite has had no apparent influence upon ore deposition. It 
 thus appears that the occurrence of two or more favorable factors is 
 necessary to determine the position of a pay shoot in a lode. The 
 discovery of these factors is one of the unsolved problems connected 
 with the Cripple Creek district. 
 
 Replacement deposits in granite. The replacement deposits in 
 granite all occur in close proximity to the contact with the breccia, 
 and are well developed in the Elkton (Thompson), Ajax, Independence, 
 and Portland mines. Although these bodies of ore are related to fis- 
 sures and occur particularly where several fissures intersect, or where 
 they meet a dike, the ore is not confined to the actual fractures. The 
 rock in the vicinity of these fissures is often extensively altered. The 
 change from altered to unaltered rock, while never perfectly sharp, is 
 often fairly abrupt and may take place within a distance of a few feet. 
 The most obvious characteristic of the metamorphosed rock is a porous 
 texture and a change of the reddish color of the normal granite to 
 grayish or greenish tints. Closer examination shows that, while the 
 porphyritic aggregates of pink microcline, so prominent in the Pikes 
 
LINDGREN AND 
 
 RANSOME. 
 
 ] TYPES OP DEPOSITS. 25 
 
 Peak type of granite, may remain unaltered, the rest of the rock, con- 
 sisting originally of microcline, oligoclase, quartz, and biotite, may be 
 completely recrystallized as a porous, vuggy aggregate of secondary 
 orthoclase(valencianite), quartz, fluorite, pyrite, calaverite or sylvanite, 
 and, in exceptional cases, sphalerite and galena. The ore minerals are 
 partly inclosed in the other secondary minerals, but occur most abun- 
 dantty with little projecting crystals of fluorite, quartz, and valencianite 
 on the walls of the irregular pores so characteristic of the altered rock. 
 The biotite of the original granite yields most readity to alteration, and, 
 in rock otherwise almost entirely unaltered, may be changed to an 
 aggregate of fluorite, quartz, and ore minerals. Some of the ore of 
 the Ajax mine exhibits well this initial stage of alteration. With fur- 
 ther alteration the original quartz and oligoclase of the granite are 
 attacked. The quartz, originally in large homogeneous and irregular 
 grains, recrystallizes as aggregates. Secondaiy orthoclase or valenci- 
 anite forms often in clear, sharply idiomorphic crystals, which either 
 project into open cavities or form aggregates with the secondary quartz. 
 In many cases, however, the secondary valencianite results from the 
 recrystallization of the older microcline practically in place. The two 
 generations are sometimes distinguishable by the greater clearness and 
 more or less idiomorphic form of the younger mineral and the absence 
 of the characteristic microcline twinning. But it is often impossible 
 to determine the line between feldspar which, from its association with 
 quartz and fluorite, is clearly secondary and the original microcline of 
 the granite. Occasionally a little calcite may be detected in the 
 altered granite, but this is rare. The original apatite and zircon of 
 the granite are not, so far as observed, affected by the alteration 
 described. 
 
 While the replacement deposits in granite are important because of 
 their size and the readiness with which the ore may be mined free 
 from waste, the ore itself is usually of lower grade than that formed 
 in the fissures of the sheeted zones. 
 
 Mineralized "basalt" dikes. The ore bodies formed by the minerali- 
 zation of basic dikes are in some ways closely related to the sheeted zones 
 already described. Like the phonolite dikes, the "basalt" exhibits 
 a pronounced tendency to split into thin sheets parallel with the dike 
 walls. Normally, the minute fissures so formed are filled with veinlets 
 of calcite and contain no ore. When, however, a zone of fissuring 
 coincides with the dike the latter may be traversed by veinlets of 
 quartz and fluorite carrying sylvanite or calaverite, while the body of 
 the dike may be impregnated with pyrite. Such ore differs from that 
 of the usual sheeted zones in breccia or phonolite in that the tellurides 
 are not so clearly confined to the actual fissures, but appear to some 
 extent to permeate the rock with the pyrite. The richest portion of 
 the ore, however, undoubtedly occurs in the small veinlets in the diko, 
 
26 RESURVEY OF CRIPPLE CREEK DISTRICT. [BULL. 254. 
 
 and usually near one or both walls where the fissuring is best devel- 
 oped. The occurrence of rich ore bodies in basic dikes in the Port- 
 land (Anna Lee), Moose, Elkton, Conundrum, Pinto, and other mines 
 has tended to exaggerate the importance of these dikes in general, 
 and some have even supposed a genetic relation to exist between 
 them and the mineralization of the district. a Such an hypothesis, 
 however, loses sight of the vast amount of profitless work that has 
 been expended in the district in driving on the usually unproduc- 
 tive basaltic dikes, and the very small proportion of the known ore 
 bodies that can be shown to have any connection whatever with these 
 intrusions. That the basaltic dikes are not always readily mineralized 
 even when accompanied by fissuring is shown in the interesting case 
 of the Strong mine, where the ore occurs as mineralized granite on 
 each side of the dike, while the latter is barren. 
 
 DEPTH OF OXIDIZED ZONE. 
 
 At a few points, as in the Abe Lincoln and El Paso mines, tellurides 
 are found almost at the surface. It is much more common, however, 
 to find an upper zone, from 200 to 400 feet deep, in which free gold 
 prevails and which gradually changes to the zone of pure telluride 
 ores. As may be expected from the varying surface form and condi- 
 tions of drainage, there is great range in the depth attained by oxida- 
 tion. Partial oxidation extends in many mines to a depth of over 
 1,000 feet, especially along the often more or less open fissures. In 
 the Wild Horse mine the zone of complete oxidation reaches a depth 
 of 1,100 feet and then suddenly ends. In the Isabella mine partial 
 oxidation attained at least 1,200 feet, and the same applies to the Gold 
 Coin mine in Victor, although telluride ores prevail at that depth as 
 well as in many levels above. The question is chiefly one of depth of 
 ground water and of facilities for circulation of oxygen. Further 
 data bearing upon this problem may be found on page 31. 
 
 RELATIONS OF ORE BODIES TO DEPTH. 
 
 It is well known that the payable ores in auriferous lodes are rarely 
 equally distributed in the lode, but form tabular bodies of more or less 
 regular outline. The projections of these ore bodies on the plane of 
 the lode often appear as elongated areas with greater vertical than 
 horizontal extent. The ore bodies or shoots of Cripple Creek show 
 great similarity to those of other gold-bearing veins; their limit in 
 depth is usually as well defined as their extent in a horizontal direction. 
 
 Of sixty pay shoots of Cripple Creek mines plotted together for 
 
 aStevens, E. A., Basaltic zones as guides to ore deposits in the Cripple Creek district: Trans. Am. 
 Inst. Min. Eng., vol. 33, 1903, p. 686. 
 
L1N K D ANsoME ND ] RELATIONS OF ORE BODIES TO DEPTH. 27 
 
 purposes of comparison, over thirty extended from the surface to a 
 depth of less than 500 feet. The maximum individual production of 
 these is less than $1,000,000. Near six of these ore bodies further 
 exploration developed new shoots below the old ones, but usually of 
 smaller extent. In practically all thirty cases the development work 
 hud been carried down a few hundred feet below the last ore of the 
 surface shoot. The form of these smaller shoots is often equidimen- 
 sional; in a few cases the horizontal extent is greater than the verti- 
 cal, or the shoot is wholly irregular; in many cases the shoot pitches 
 steeply northward on the plane of the vein and the ratio of vertical to 
 horizontal extent is 2:1 or 3:1. 
 
 In eight of the sixty cases the shoot extended from the surface to a 
 depth of 1,000 feet, or a little more, and ended. Further development 
 to about 1,500 feet failed to find new shoots of any importance, though 
 small pockets were often discovered. In six of these eight cases the 
 ratio of vertical to horizontal extent varies from 3:1 to 5:1, and 
 the shoots usually pitch northward at angles of 60 to nearly 90 from 
 the horizontal. In the remaining two cases the shoots have about the 
 same horizontal as vertical extent. The maximum horizontal length 
 is 1,300 feet, while 400 is much more common. In two of the sixty 
 cases the pay shoot is 1,500 to 2,000 feet long, maximum depths of 
 600 and 1,000 feet having been attained and the bottom level being still 
 in ore. In thirteen of the sixty cases the shoot began over 200 feet 
 below the surface; in eight of these the bottom of the shoot has been 
 reached, while in five the lowest level is still in ore. Steeply dipping, 
 irregular elongated forms prevail. Many of this group of thirteen 
 represent veins parallel and close to those on which pay shoots out- 
 cropping at the surface were found. 
 
 These statements will give an idea of the form of the shoots. Of 
 course, in the case of shoots reaching the surface, a certain part has 
 probably been removed by erosion. Judging from the shoots which 
 distinctly began below the surface, the normal form of the ore bodies 
 is elongated, vertical, or pitching sharply northward, the ratio of ver- 
 tical to horizontal extension varying from li : 1 to 5:1. Some of 
 these shoots are, however, of about equal dimensions, vertically and 
 horizontally, while in a few the horizontal dimension is the greater. 
 
 Of the known ore bodies, as few exceed 1,000 feet in length, so 
 very few exceed 1,000 feet in depth or extend more than 1,000 feet 
 from the surface. Speaking broadly, explorations below that limit have 
 not proved very satisfactory. Drawing the lines a little closer, it may 
 be said that in proportion to the amount of exploration the upper 700 
 or 800 feet have yielded more than the interval frpm that limit to the 
 lowest levels reached about 1,500 feet. It must not be overlooked, 
 however, that four or five mines still have good ore bodies at a depth 
 
28 RESURVEY OF CRIPPLE CREEK DISTRICT. [BULL. 254. 
 
 of 1,200 to 1,400 feet from the surface. The developments of the 
 next year or two will probably give a safer basis for generalization. 
 
 Roughly speaking, the above-mentioned distribution holds good for 
 any elevation within the district. In other words, the principal pro- 
 ductive zone everywhere occupies the space from the surface down 
 to about 1,000 feet below it, and its lower limit thus forms a curved 
 surface approximately parallel to the surface of the ground. 
 
 It is probable that the minimum depth of rock removed from the 
 district by erosion amounts to 1,000 feet in the central part and to 
 400 or 500 feet about the periphery. The shape and number of the 
 ore bodies formerly existing in this eroded zone can be only conjec- 
 tured. It is probable that the veins were formed shortly after the 
 close of igneous activity, while the volcano yet possessed a much 
 greater height than at present. The absence of hot waters and the 
 depth of oxidation attained indicate that vein formation at Cripple 
 Creek is by no means a recent phenomenon. 
 
 The general features of the vertical distribution of the known ore 
 bodies recorded above have of late years received more or less recog- 
 nition, and there has been a decided tendency to attribute them to a 
 process of secondary enrichment effected by waters moving generally 
 downward from the surface. It has been supposed a that such waters 
 have carried down a part of the auriferous contents of those portions 
 of the lodes now removed by erosion and have enriched originally lean 
 pyritic ores by the secondary deposition of gold and silver tellurides 
 and argentiferous tetrahedrite, with associated gangue minerals. 
 
 It is clear that the hypothesis in question is suggested by the dis- 
 tribution of known pay shoots. The question arises, How far does 
 the distribution of known pay shoots represent the distribution of all 
 the pay shoots in the district? In other words, How far has explora- 
 tion been impartial in revealing ore bodies near the surface and at 
 depths greater than 1,000 feet? 
 
 It requires but little examination to make clear the fact that ore 
 bodies within 1,000 feet of the surface are far more likely to be discov- 
 ered than those at greater depth. While shafts have been sunk for a 
 few hundred feet without any indication of ore and have ultimately 
 been developed into productive mines, such a procedure is considered 
 bold prospecting, and few well-informed mining men would seriously 
 contemplate sinking a shaft over 1,000 feet in depth solely on the 
 expectation of finding possible ore bodies below that depth. Most of 
 the large mines in the district have started upon some indication of ore 
 near the surface and have grown by the subsequent discovery of other 
 lodes and ore bodies in the course of their underground development. 
 As few individual ore bodies persist for more than 1,000 feet in depth, by 
 
 a Bancroft, Geo. J., Eng. and Min. Jour., vol. 74, 1902, pp. 752-753, and vol. 75, 1903, pp. 111-112. 
 Finch, J. W., Proc. Colorado Sci. Soc., vol. 7, 1904, pp. 193-252. 
 
LIN R I SfsoMK ND ] RELATIONS OF ORE BODIES TO DEPTH. 29 
 
 far the greater part of the underground prospecting is at less depths, 
 there being usually little inducement to go deeper, unless, as in the 
 case of the Gold Coin and Portland mines, lodes are discovered in 
 which the ore, beginning several hundred feet below the surface, 
 extends deeper than the pay shoot upon which the mine was origi- 
 nally opened. Thus deep prospecting is usually confined to the 
 vicinity of the larger and more persistent pay shoots which have been 
 followed down from near the surface. Underground water has also 
 proved a most serious obstacle to deep prospecting, few properties 
 being able to develop below the 1,000-foot zone unless there is abun- 
 dant and high-grade ore in sight. 
 
 It may thus be concluded, without necessarily advocating promiscu- 
 ous exploration below the 1,000-foot zone, that any ore bodies exist- 
 ing below that depth are far less likely to be discovered than those 
 above, where from the surface to depths of several hundred feet the 
 rocks of the district are riddled with shafts, drifts, crosscuts, and 
 adits. It is exceedingly difficult, however, to determine, even ap- 
 proximately, the relative importance of this factor in the problem. 
 It is probably safe to assume that th.e chances of discovering a given 
 ore body within the 1,000-foot zone are at least ten times those of dis- 
 covering an ore body below that zone, and the ratio may be very much 
 greater. It is probably true that there was originally more ore within 
 the 1,000-foot zone than there is in a corresponding zone below, but 
 this disparity is not necessarily anything like so great as is indicated 
 by the vertical distribution of known pay shoots. 
 
 Another important line of inquiry bearing upon the relations of the 
 ore bodies to depth is concerned with the question of the relative size 
 and abundance of the fissures near the surface and at greater depth. It 
 has been shown that all the ore bodies are intimately connected with 
 fissures. If such fissures are generally smaller and less abundant 
 below the 1,000-foot zone than they are within it, obviously there is 
 introduced a factor which diminishes the supposed importance of sec- 
 ondary enrichment by affording an anterior and physical explanation 
 for the decrease of ore with increase of depth. 
 
 Detailed examination of practically all the accessible mines in the 
 Cripple Creek district has led to the conclusion that the fissures, which 
 ordinarily are narrow and often appear as mere cracks, do become less 
 abundant and less conspicuous as greater depth is attained. No mine 
 exhibits this feature better than the Stratton's Independence, in which 
 the very complex systems of productive fissures on the fifth and higher 
 levels contrast most strikingly with the few, insignificant, and unpro- 
 ductive fractures visible on the fourteenth level. In less degree the 
 same feature is shown in many others of the deep mines, but the rule 
 is not without some very marked exceptions. 
 
30 RESURVEY OF CRIPPLE CREEK DISTRICT. [BULL. 264. 
 
 The dependence of the ore zone on the surface would thrn merely 
 express the depth to which fissuring extended in a conical volcanic 
 mountain. 
 
 We have thus two factors of importance to account for the scarcity 
 of ore shoots below the 1,000-foot level first, difficulties of develop- 
 ment and exploration, and second, the disappearance of fissures in 
 depth. They do not seem to be sufficient, however, and it is believed 
 that a third factor, as yet undiscovered, exists, and that it is related to 
 the chemistry of the actual ore deposition. 
 
 In those districts where so-called secondary sulphide enrichment is 
 known to have taken place the ore minerals exhibit irr general an 
 orderly sequence, both in relative abundance and in kind, from those 
 characteristic of the most highly enriched ore near the zone of oxida- 
 tion to those constituting the original, lean, and unaltered ore. The 
 secondary minerals produced are such as can result from rearrange- 
 ment and concentration of elements present in different combinations 
 in the primary ores. At certain points within this range of alteration 
 it is possible to detect direct mineralogical evidence of the change of 
 one mineral to another, effected by solutions moving downward from 
 the zone of oxidation. In most cases the secondarily enriched ores 
 bear a recognizable relation to the lower limit of oxidation. 
 
 Careful study of the Cripple Creek ore deposits has failed to discover 
 that the hypothesis of secondary enrichment is supported by crucial 
 evidence of the kind just indicated. The minerals are not arranged 
 in any discoverable definite sequence, nor does the present investiga- 
 tion find much to support the view that the rich telluride ores, as a 
 rule, pass with increasing depth into low-grade pyritic ores. Fre- 
 quently such ore as occurs below a depth of 1,000 feet is precisely the 
 same in character as ore found within 100 feet of the surface. Tetra- 
 hedrite, which has been regarded by some, without definite proof, as a 
 secondary mineral, occurs sporadically throughout the district and at 
 all depths reached by present workings. The richest ore does not 
 uniformly occur immediately below the oxidized ore. There is, in 
 fact, little indication of enrichment in the oxidized zone such as is so 
 often found in gold-quartz veins of the normal type. Frequently the 
 fresh telluride ore is extremely j*ich, and high-grade pockets occur 
 impartially in oxidized and fresh portions of the veins. Neither 
 would it be correct to say that there is a gradual decrease in the value 
 of ore in depth. It is quantity, not value, which decreases. 
 
 While it is certain that pyrite, and possibly other minerals, has 
 formed at more than one period during the mineralization of the dis- 
 trict, and while it is equally clear that in general the rich tellurides 
 were the last of the ore minerals to be deposited, there is apparently 
 no evidence that any one of these minerals has been formed by enrich- 
 ing solutions at the expense of primary minerals. So far as definite 
 
] UNDERGROUND WATER. 31 
 
 conclusion is warranted in an investigation as yet incomplete, it 
 appears that the unoxidized ore deposits of the Cripple Creek district 
 represent the product of one general period of mineralization and that 
 they have not been appreciably modified by secondary enrichment 
 during the subsequent erosion of the region. 
 
 UNDERGROUND WATER. 
 
 The conditions of underground waters are interesting and somewhat 
 unusual. A dry climate and a heavy percentage of run-off minimize 
 the annual additions to the underground supply. Nevertheless, the 
 ground-water level is not unusually deep, and large quantities of water 
 are encountered in all the mines below that level. The original water 
 surface of the district in the volcanic rocks stood at elevations of 9,400 
 to 9,700 feet, or 100 to 600 feet below the surface of the ground. At 
 first pumping was commenced by individual mines, but it was soon 
 found that the radius of drainage had unusual length that is, that one 
 mine would drain others situated at a distance. Drainage tunnels were 
 then undertaken, and the Chicago and Cripple Creek, the Ophelia, the 
 Standard, and lately the El Paso tunnels were driven, each of which 
 practically accomplished the drainage of a large part of the district 
 almost down to its own level, thus showing that the ground water is 
 limited in quantity and is more of the nature of a local reservoir than 
 a ' ' subterranean sea. " 
 
 The plug of volcanic rocks which fills the throat of. the old volcano 
 is rudely circular, with a diameter of 3 miles. This mass is extremely 
 porous, and is, moreover, cut in many directions by partly filled fissures 
 and sheeted zones, so that water can circulate within it with compara- 
 tive freedom in several directions. It retains this character down to 
 the greatest depth yet reached. On the other hand, the surrounding 
 granite is relatively impermeable and is less traversed by open fissures. 
 No doubt it contains ground water down to a depth of 2,000 feet or 
 more, but in very much smaller quantity, and the circulation of this 
 water must be extremely slow. This is clearly shown by the fact that 
 the water in the breccia is not drained by Cripple Creek and Arequa 
 Gulch below the level of the points where they leave the volcanic area. 
 Thus the volcanic plug resembles a water-soaked sponge inserted in a 
 hole cut in an impermeable substance. The drainage of the mines is 
 thereby greatly facilitated, as it is not necessary to extend the tapping 
 tunnels to each mine. 
 
 The El Paso tunnel, completed in the winter of 1903-4, has an ele- 
 vation of 8,790 feet at the portal. Within a short time it effectually 
 drained not only the Beacon Hill mines but also the Gold Hill mines, 
 and its influence extended even to the Last Dollar and the Elkton 
 mines. But the foregoing statement in relation to draining the dis- 
 
32 RESURVEY OF CRIPPLE CREEK DISTRICT. [BULL. 254. 
 
 trict must be so modified as to exclude a certain part on the eastern 
 side, comprising the mines about Independence on the east side of Bull 
 Hill and those on Battle Mountain and in the town of Victor, in which 
 the effect of the El Paso tunnel is slight. The Findley, Hull City, 
 Vindicator, and Golden Cycle mines about the town of Independence 
 seem to occupy a separate drainage basin, probably divided from the 
 main area by masses of relatively impermeable rock. 
 
 The Portland, Stratton's Independence, and the other mines near 
 Victor occupy another drainage basin. Of these the Gold Coin and 
 the Stratton's Independence have shafts below the level of the El Paso 
 tunnel, and their pumps have probably drained the surrounding terri- 
 tory to a considerable extent. The influence of the drainage tunnel 
 on the Portland mine is a question upon which opinions differ. 
 
 The subject of the drainage of the Cripple Creek mines has been 
 actively studied in late years, and valuable contributions to the subject 
 have been made by Mr. Victor G. Hills and others, who have shown 
 that the water can be tapped, without prohibitive expense, down to an 
 elevation of 7,500 feet, or 1,300 feet below the El Paso tunnel; for 
 this depth a tunnel 3 miles long would be needed. On account of the 
 great porosity of the rocks it is not probable that the next thousand 
 feet below, the El Paso tunnel level will show any great diminution in 
 the amount of water stored in the rocks. 
 
 SUBTERRANEAN GASES. 
 
 During the earlier years of Cripple Creek no unusual amount of 
 mine gases was observed, but, as the shafts and workings deepened, 
 several properties began to experience much annoyance and even 
 serious interference with work, often in spite of vigorous measures 
 for ventilation. These gases appear to issue chiefly from the breccia, 
 especially where it is of porous and loose texture, but they sometimes 
 flow from partly open vein fissures in such quantity that a light held 
 up to the fissures is immediately extinguished. Thus far the mines 
 on Battle Mountain and those of the Golden Cycle, Vindicator, and 
 Isabella groups have suffered no inconvenience, but most of the mines 
 west of this line have had more or less trouble with this subtle and 
 insidious enemy. At least one mine has been forced to close down 
 entirely, and several others are often obliged to abandon work for 
 days. Sometimes the amount of gas issuing is small, and ordinary 
 ventilation will carry it away; again it may issue in large volumes 
 and practically fill the mine for some time. In other mines the gas 
 persistently hangs at certain places, forming barriers which can be 
 passed only with difficulty. The outflow of gas is unquestionably 
 related to barometric fluctuations, though it is usually locally reported 
 
] SUBTERRANEAN GASES. 33 
 
 to be influenced by the direction of the wind. The investigations 
 concerning this subject are not yet concluded. It may be said, how- 
 ever, that a sudden lowering of the barometer seems to be the most 
 important factor. Upon such a fall the gas issues in great volumes, 
 but decreases when the barometer remains steadily low for several 
 days. The gas is often very heavy, filling lower parts of drifts and 
 winzes like water, and cases are reported in which it has actually been 
 bailed from a shaft. Its temperature is somewhat higher than that 
 prevailing in the mine under normal conditions. 
 
 It has practically no smell or taste, but small quantities of it easily 
 produce effects of suffocation. Miners working in places where this 
 gas is mixed with the air soon experience various forms of physical 
 distress, and several fatal accidents have been caused by men entering 
 drifts and winzes filled with it. 
 
 The characteristics of the gas seemed to point to carbon dioxide, 
 and it is generally so termed. Preliminary determinations of carbon 
 dioxide by a portable apparatus yielded percentages which seemed far 
 too small in comparison with the effects of the gas examined, and led 
 to the belief that some other substance was present. Samples were 
 then collected and analyzed. The analyses showed the gas to be a 
 mixture of nitrogen with about 20 per cent carbon dioxide and a small 
 amount of oxygen. 
 
 The occurrence of these exhalations over a large part of the ore- 
 bearing area is of much interest. They certainly increase in quantity 
 with depth, and it is to be feared that in some cases they may seriously 
 affect mining operations. The evil has proved very difficult to cope 
 with. Ventilation alone has rarely proved efficient, and the only 
 practicable remedial measures appear to be cementation of drifts at 
 particularly bad places and working the mine under air lock at a pres- 
 sure slightly exceeding the normal. 
 
 The origin of these gases can not reasonably be sought in any such 
 explanation as the oxidizing of sulphides and accompanying absorption 
 of oxygen. We believe that they represent the last exhalations from 
 the throat of the extinct Cripple Creek volcano. 
 
 FUTURE OF THE DISTRICT. 
 
 To predict the future yield of any mining district is no easy task; 
 the conditions under which most ores are deposited are as yet too 
 imperfectty understood, and the deposits themselves are usually too 
 erratic in form and distribution, to give certitude to such predictions, 
 even when these are based upon a careful study of the history and 
 present condition of a district. Nevertheless, it is part of the duty of 
 the geologists who have officially investigated the Cripple Creek dis- 
 trict to interpret to the best of their ability the bearing of ascertained 
 Bull. 25405 3 
 
34 RESURVEY OF CRIPPLE CREEK DISTRICT. [BULL. 254, 
 
 facts upon future mining development. For such a forecast of the 
 future moderate probability is all that can be claimed. 
 
 As has been pointed out in the preceding pages, the largest known 
 ore bodies of the district are apparantly confined within a zone which 
 extends from the surface to a depth of 1,000 feet. In general, explo- 
 rations below that depth have been much less satisfactory, as regards 
 quantity of ore, than explorations above. It is certainly true that 
 some large ore bodies as yet show no sign of depletion in depth, and 
 that some good pay shoots have been found at a depth of 1,400 to 
 1,500 feet. On the other hand, the number of ore shoots that have 
 been exhausted with increase in depth is considerable. 
 
 It is probable that the ore bodies, known or unknown, occurring 
 below the 1,000-foot zone are neither so large nor so abundant as 
 those nearer the surface. The discovery and exploitation of these 
 (Jeeper ore bodies is, moreover, beset with increasing difficulties, chief 
 among which is the problem of dealing with the underground water. 
 For these reasons it is unlikely that the zone between the 1,000-foot 
 and 2,000-foot levels will yield as much as the zone between the sur- 
 face and the 1,000-foot level, but the possibility is not denied that 
 sorce strong fissures may carry payable ore to far greater depths than 
 those jet attained. 
 
 As regards the zone above the 1,000-foot or 1,500-foot level, it is 
 well to bear in mind that it still contains much ore, both as parts of 
 known ore shoots and as yet undiscovered ore bodies. It is certain 
 that many of these undeveloped ore bodies will be mined in the near 
 future and that this zone will contribute the most important part of 
 the production. 
 
 It is probable that the production of the district, while exhibiting 
 fluctuations, will on the whole slowly decline. New ore bodies will 
 undoubtedly be discovered from time to time, and individual mines 
 may be as profitable in the future as they have been in the past, or 
 even more profitable. An increased output may be expected to 
 follow each successful step in deep drainage. But existing conditions 
 indicate that if the maximum production of $18,000,000, in 1900, is to 
 be surpassed the increase will be due to the ore bodies encountered in 
 the upper zone. 
 
INDEX. 
 
 Page. 
 
 Abe Lincoln mine, location of 16 
 
 Ajax mine, depth of 19 
 
 Anaconda mine, production of 16 
 
 Anchoria-Leland mine, production and 
 
 depth of 16 
 
 Bancroft, G. J., on downward -moving 
 
 waters 28 
 
 Basalt dikes, ore in 25-26 
 
 Battle Mountain vein system, mines on 18 
 
 Beacon Hill, mines on 17 
 
 Breccia, occurrence and character of ... 12, 13-14 
 
 Bruce, J., work of 8 
 
 Bull Hill, mines on 17 
 
 Calaverite, composition of 20 
 
 Calcite, occurrence of 21 
 
 Carbonate Hill, prospects on 20 
 
 Celestite, occurrence of 21 
 
 Chlorination process, use of 10 
 
 Conundrum mine, depth of 16 
 
 Cripple Creek granite, occurrence of 13 
 
 Cross, Whitman, work of 7, 11 
 
 Cyanide process, use of 10 
 
 Damon mine, location of 17 
 
 Dikes, mineralized basalt, description of .. 25-26 
 Doctor-Jack Pot mine, production and 
 
 depth of 16 
 
 Dolomite, occurrence of 21 
 
 Douglas, E. M., work of 7 
 
 El Paso shaft, depth of 15 
 
 Elkton mine, production and depth of 17 
 
 JElkton shaft, depth of 15 
 
 Evans, R. T., work of 7 
 
 Feldspar, occurrence of 21 
 
 Finch, J. W., acknowledgments to 7 
 
 Finch, J. W., on downward-moving waters. 28 
 
 Fissures, character of 22 
 
 See also Veins: 
 
 Fluorine mine, production of 20 
 
 Fluorite, occurrence of 21 
 
 Galena, occurrence of 20 
 
 Gangue minerals, description of 21 
 
 Gases, subterranean, discussion of 32-33 
 
 Globe Hill, mines on 16 
 
 Gold, discovery of, date of 7, 8 
 
 production of 8-9 
 
 See also Ores. 
 
 Gold Coin mine, production of is 
 
 Gold Coin shaft, depth of. 15, 19 
 
 Gold Hill, mines on 16 
 
 <3old King mine, production of 16 
 
 -Golden Cycle mine, production of is 
 
 Page. 
 Granite, occurrence and character of ... 11, 12-13 
 
 replacemen t deposits in 24-25 
 
 Graton, L. C., work of 8 
 
 Half Moon mine, production of 16 
 
 Hills, V. G., work of 32 
 
 Hull City mine, production of 18 
 
 Igneous rocks, occurrence and character of. 11-14 
 
 Independence mine, production of 19 
 
 Independence shaft, depth of 15 
 
 Isabella mine, oxidation in, depth of 26 
 
 production and depth of 18 
 
 Jerry Johnson mine, location of 17 
 
 Last Dollar mine, production and depth of. 18 
 
 Lillie mine, production of 18 
 
 Lillie shaft, depth of 9, 15, 18 
 
 Map, topographic, revision of 7-8 
 
 Mary McKinney mine, depth of 16 
 
 Metallurgy and mining, discussion of 9-10 
 
 Midget mine, production and depth of 16 
 
 Mineralized basalt dikes, description of 25-26 
 
 Minerals, description of 20-21 
 
 Mines, area including 14 
 
 description of 15-20 
 
 methods of working 9 
 
 Mining and metallurgy, discussion of 9-10 
 
 Moon-Anchor mine, production of 16 
 
 Moose mine, production of 17 
 
 Rock, A. M., work of 8 
 
 Ore bodies, relation of, to depth 26-31 
 
 structure of 22 
 
 types of 22-26 
 
 Ores, character of 20-21 
 
 treatment of 10 
 
 Oxidized ores, occurrence and character of. 21 
 
 Oxidized zone, depth of 26 
 
 Penrose, R. A. F., jr., work of 7,14 
 
 Phonolite, occurrence of 12 
 
 Pikes Peak granite, occurrence of 12 
 
 Pinnacle mine, location of 17 
 
 Portland mine, production of 10, 19 
 
 Portland vein system, mines on * 19 
 
 Poverty Gulch, mines near 16 
 
 Production of gold, table showing 9 
 
 Productive area, extent of 14 
 
 Pyrite, occurrence of 20 
 
 Quartz, occurrence of ' 21 
 
 Raven Hill, mines on 17 
 
 Replacement deposits in granite, descrip- 
 tion of 24-25 
 
 Rhodochrosite. occurrence of 21 
 
 Roscoelite, occurrence of 21 
 
 35 
 
INDEX. 
 
 Page. 
 
 Shafts, depth of 15 
 
 Sheeted veins, description of 23 
 
 Silver, occurrence of, in ores 21 
 
 production of 9 
 
 Sphalerite, occurrence of 21 
 
 Stevens, E. A., on basalt dikes 26 
 
 Strong mine, production and depth of 19 
 
 Structure of ore bodies, description of 22 
 
 Sylvanite, composition of 20 
 
 Tellurides, occurrence of 20 
 
 Topographic map, revision of 7-8 
 
 Topography, description of 11 
 
 Tuff and breccias, occurrence and character 
 
 of... 12 
 
 Page. 
 
 Underground development, extent of 15 
 
 Underground water, discussion of 31-32 
 
 Veins, sheeted, description of 23 
 
 Victor mine, production and depth of 18 
 
 Vindicator mine, production and depth of. 18 
 
 Vindicator vein system, mines of 18 
 
 Volcanic rocks, occurrence and character of 11-14 
 
 W. P. H. mine, location of 17 
 
 Water, underground, discussion of 31-32 
 
 Wild Horse mine, oxidation in, depth of. . . 26 
 production of IT 
 
 o 
 
 
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 [Bulletin No. 254.] 
 
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 W. R. Crane. 1904. 83 pp., 11 pis. 
 
 B 243. Cement materials and industry of the United States, by E. C. Eckel. 1905. pp., 15 pis. 
 B 246. Zinc and lead deposits of northwestern Illinois, by H. Foster Bain. 1904. 56 pp., 5 pis. 
 B 247. The Fairhaven gold placers, Seward Peninsula, Alaska, by F. H. Moffit. 1905. pp., 14 pis. 
 B 249. Limestones of southwestern Pennsylvania, by F. G. Clapp. 1905. pp., 7 pis. 
 B 250. The petroleum fields of the Pacific coast of Alaska, with an account of the Bering River coal 
 
 deposit, by G. C. Martin. 1905. pp., 7 pis. 
 B 251. The gold placers of the Fortymile, Birch Creek, and Fairbanks regions, Alaska, by L. M. 
 
 Prindle. 1905. pp., 16 pis. 
 WS 117. The lignite of North Dakota and its relation to irrigation, by F. A. Wilder. 1905. pp., 
 
 pis. 
 PP 36. The lead, zinc, and fluorspar deposits of western Kentucky, by E. O. Ulrich and W. S. Tangier 
 
 Smith. 1905. pp., pis. 
 PP 38. Economic geology of the Bingham mining district of Utah, by J. M. Boutwell, with a chapter 
 
 on areal geology, by Arthur Keith, and an introduction on general geology, by S. F. Emmons. 
 
 1905. pp., pis. 
 PP 41. The geology of the central Copper River region, Alaska, by W. C. Mendenhall. 1905. pp., 
 
 -pis. 
 
 B 254. Report of progress in the geological resurvey of the Cripple Creek district, Colorado, by Walde- 
 mar Lindgren and F. L. Ransome. 1904. 36 pp. 
 
 SERIES B, DESCRIPTIVE GEOLOGY. 
 
 B 23. Observations on the junction between the Eastern sandstone and the Keweenaw series on 
 
 Keweenaw Point, Lake Superior, by R. D. Irving and T. C. Chamberlin. 1885. 124pp., 
 
 17 pis. 
 
 B 33. Notes on geology of northern California, by J. S. Diller. 1886. 23pp. (Out of stock.) 
 B 39. The upper beaches and deltas of Glacial Lake Agassiz, by Warren Upham. 1887. 84 pp., 1 pi. 
 
 (Out of stock.)- 
 B 40. Changes in river courses in Washington Territory due to glaciation, by Bailey Willis. 1887. 
 
 10pp., 4 pis. (Out of stock.) 
 B 45. The present condition of knowledge of the geology of Texas, by R. T. Hill. 1887. 94 pp. (Out 
 
 of stock.) 
 
 B 53. The geology of Nantucket, by N. S. Shaler. 1889. 55pp., 10 pis. (Out of stock.) 
 B 57. A geological reconnaissance in southwestern Kansas, by Robert Hay. 1890. 49 pp., 2 pis. 
 B 58. The glacial boundary in western Pennsylvania, Ohio, Kentucky, Indiana, and Illinois, by G. F. 
 
 Wright, with introduction by T. C. Chamberlin. 1890. 112 pp., 8 pis. (Out of stock. ) 
 B 67. The relations of the traps of the Newark system in the New Jersey region, by N. H. Darton. 
 
 1890. 82pp. (Out of stock.) 
 S 104. Glaciation of the Yellowstone Valley north of the Park, by W. H. Weed. 1893. 41 pp., 4 pis. 
 
ADVERTISEMENT. Ill 
 
 B 108. A geological reconnaissance in central Washington, by I. C. Russell. 1893. 108 pp., 12 pis, 
 (Out of stock.) 
 
 B 119. A geological reconnaissance in northwest Wyoming, by G. H. Eldridge. 1894. 72 pp., 4 pis. 
 
 B 137. The geology of the Fort Riley Military Reservation and vicinity, Kansas, by Robert Hay, 
 1896. 35 pp., 8 pis. 
 
 B 144. The moraines of the Missouri Coteau and their attendant deposits, by J. E. Todd. 1896. 71 
 pp., 21 pis. 
 
 B 158. The moraines of southeastern South Dakota and their attendant deposits, by J. E. Todd. 
 1899. 171 pp., 27 pis. 
 
 B 159. The geology of eastern Berkshire County, Massachusetts, by B. K. Emerson. 1899. 139 pp., 
 9 pis. 
 
 B 165. Contributions to the geology of Maine, by H. S. Williams and H. E. Gregory. 1900 212 pp., 
 14 pis. 
 
 WS 70. Geology and water resources of the Patrick and Goshen Hole quadrangles in eastern Wyo- 
 ming and western Nebraska, by G. I. Adams. 1902. 50 pp., 11 pis. 
 
 B 199. Geology and water resources of the Snake River Plains of Idaho, by I. C. Russell. 1902. 192 
 pp., 25 pis. 
 
 PP 1. Preliminary report on the Ketchikan mining district, Alaska, with an introductory sketch of 
 the geology of southeastern Alaska, by A. H. Brooks. 1902. 120 pp., 2pls. 
 
 PP 2. Reconnaissance of the northwestern portion of Seward Peninsula, Alaska, by A. J. Collier. 
 1902. 70 pp., 11 pis. 
 
 PP 3. Geology and petrography of Crater Lake National Park, by J. S. Diller and H. B. Patton. 
 1902. 167pp., 19 pis. 
 
 PP 10. Reconnaissance from Fort Hamlin to Kotzebue Sound, Alaska, by way of Dall, Kanuti. Allen, 
 and Kowak rivers, by W. C. Mendenhall. 1902. 68 pp., 10 pis. 
 
 PP 11. Clays of the United States east of the Mississippi River, by Heinrich Ries. 1903. 298 pp., 9 pis. 
 
 PP 12. Geology of the Globe copper district, Arizona, by F. L. Ransome. 1903. 168 pp., 27 pis. 
 
 PP13. Drainage modifications in southeastern Ohio and adjacent parts of West Virginia and Ken- 
 tucky, by W. G. Tight. 1903. Ill pp., 17 pis. 
 
 B 208. Descriptive geology of Nevada south of the fortieth parallel and adjacent portions of Cali- 
 fornia, by J. E. Spurr. 1903. 229 pp., 8 pis. 
 
 B 209. Geology of Ascutney Mountain, Vermont, by R. A. Daly. 1903. 122 pp., 7 pis. 
 
 WS 78. Preliminary report on artesian basins in southwestern Idaho and southeastern Oregon, by 
 I. C. Russell. 1903. 51 pp., 2 pis. 
 
 PP 15. Mineral resources of the Mount Wrangell district, Alaska, by W. C. Mendenhall and F. C. 
 Schrader. 1903. 71pp., 10 pis. 
 
 PP17. Preliminary report on the geology and water resources of Nebraska west of the one hundred 
 and third meridian, by N. H. Darton. 1903. 69 pp., 43 pis. 
 
 B 217. Notes on the geology of southwestern Idaho and southeastern Oregon, by I. C. Russell. 1903. 
 83 pp., 18 pis. 
 
 B 219. The ore deposits of Tonopah, Nevada (preliminary report), by J. E. Spurr. 1903. 31 pp., 1 pi. 
 
 PP 20. A reconnaissance in northern Alaska in 1901, by F. C. Schrader. 1904. 139 pp., 16 pis. 
 
 PP21. The geology and ore deposits of the Bisbee quadrangle, Arizona, by F. L. Ransome. 1904. 
 168pp., 29 pis. 
 
 WS 90. Geology and water resources of part of the lower James River Valley, South Dakota, by J. E. 
 Todd and C. M. Hall. 1904. 47 pp., 23 pis. 
 
 PP25. The copper deposits of the Encampment district, Wyoming, by A. C. Spencer. 1904. 107pp.,2pls. 
 
 PP 26. Economic resources of northern Black Hills, by J. D. Irving, with chapters by S. P. Emmons. 
 and T. A. Jaggar, jr. 1904. 222 pp., 20 pis. 
 
 PP 27. Geological reconnaissance across the Bitterroot Range and the Clearwater Mountains in Mon- 
 tana and Idaho, by Waldemar Lindgren. 1904. 122 pp., 15 pis. 
 
 PP 31. Preliminary report on the geology of the Arbuckle and Wichita mountains in Indian Terri- 
 tory and Oklahoma, by J. A. Taff, with an appendix on reported ore deposits in the Wichita 
 Mountains, by H. F. Bain. 1904. 97 pp., 8 pis. 
 
 B 235. A geological reconnaissance across the Cascade Range near the forty-ninth parallel, by G. O. 
 Smith and F. C. Calkins. 1904. 103 pp., 4 pis. 
 
 B 236. The Porcupine placer district, Alaska, by C. W. Wright. 1904. 35 pp., 10 pis. 
 
 B 237. Igneous rocks of the High wood Mountains, Montana, by L. V. Pirsson. 1904. 208 pp., 7 pis. 
 
 B 238. Economic geology of the lola quadrangle, Kansas, by G. I. Adams, Erasmus Haworth, and 
 W. R. Crane. 1904. 83 pp., 11 pis. 
 
 PP 32. Geology and underground water resources of the central Great Plains, by N. H. Darton. 1905. 
 pp., 72 pis. 
 
 WS 110. Contributions to hydrology of eastern United States, 1904; M. G. Fuller, geologist in charge. 
 1905. pp., 5 pis. 
 
 B 242. Geology of the Hudson Valley between the Hoosic and the Kinderhook, by T. Nelson Dale. 
 1904. 63pp., 3 pis. 
 
 PP 34. Delavan lobe of the Lake Michigan glacier of the Wisconsin stage of glaciation and associated 
 phenomena, by W. C. Alden. 1904. 106 pp., 15 pis. 
 
IV ADVEKTISEMENT. 
 
 PP 35.-Geology of the Perry basin in southeastern Maine, by G. O. Smith and David White. 1905. 
 
 pp. ,6 pis. 
 
 B 243. Cement materials and industry of the United States, by E. C. Eckel. 1905. pp., 15 pis. 
 
 B 246. Zinc and lead deposits of northeastern Illinois, by H. F. Bain. 1904. 56 pp., 5 pis. 
 
 B 247. The Fairhaven gold placers of Seward Peninsula, Alaska, by F. H. Moffit. 1905. pp., 14 pis. 
 
 B 249. Limestones of southwestern Pennsylvania, by F. G. Clapp. 1905. pp., 7 pis. 
 
 B 250. The petroleum fields of the Pacific coast of Alaska, with an account of the Bering River coal 
 
 deposit, by G. C. Martin. 1905. pp., 7 pis. 
 B 251. The gold placers of the Fortymile, Birch Creek, and Fairbanks regions, Alaska, by L. M. 
 
 Prindle. 1905. pp., 16 pis. 
 WS 118. Geology and water resources of a portion of east-central Washington, by F. C. Calkins. 1905. 
 
 pp., 4 pis. 
 
 B 252. Preliminary report on the geology and water resources of central Oregon, by I. C. Russell. 
 
 1905. pp., 24 pis. 
 PP 36. The lead, zinc, and fluorspar deposits of western Kentucky, by E. O. Ulrich and W. S. Tangier 
 
 Smith. 1905. pp., pis. 
 PP 38. Economic geology of the Bingham mining district of Utah, by J. M. Boutwell, with a chapter 
 
 on areal geology, by Arthur Keith, and an introduction on general geology, by S. F. Emmons. 
 
 1905. pp., pis. 
 PP 41. The geology of the central Copper River region, Alaska, by W. C. Mendenhall. 1905. pp., 
 
 -pis. 
 B 254. Report of progress in the geological resurvey of the Cripple Creek district, Colorado, by Wai- 
 
 demar Lindgren and F. L. Ransome. 1904. 36 pp. 
 
 Correspondence should be addressed to 
 
 THE DIRECTOR, 
 
 UNITED STATES GEOLOGICAL SURVEY, 
 
 WASHINGTON, D. 0. 
 DECEMBER, 1904. 
 
LIBRARY CATALOGUE SLIPS. 
 
 [Mount each slip upon a separate card, placing the subject at the top of the 
 second slip. The name of the series should not be repeated on the series 
 card, but add the additional numbers, as received, to the first entry.] 
 
 Lindgren, Waldemar, 1860- 
 
 . . . Report of progress in the geological resurvey 
 of the Cripple Creek district, Colorado; by Waldemar 
 I Lindgren and Frederick Leslie Ransome. Washing- 
 ton, Gov't print, off., 1904. 
 
 36, iii p. 23 cm . (U. S. Geological survey. Bulletin no. 254.) 
 Subject series: A, Economic geology, 49; B, Descriptive geology, 61. 
 
 1. Geology, Economic Colorado. I. Ransome, Frederick Leslie, 1868- 
 
 Lindgren, Waldemar, 1860- 
 
 . . . Report of progress in the geological resnrvey 
 of the Cripple Creek district, Colorado; by Waldemar 
 I Lindgren and Frederick Leslie Ransome. Washing- 
 Is ton, Gov't print, off., 1904. 
 
 36, iii p. 23 cm . (U. S. Geological survey. Bulletin no. 254. ) 
 Subject series: A, Economic geology, 49; B, Descriptive geology, 61. 
 
 1. Geology, Economic Colorado. I. Ransome, Frederick Leslie, 1868- 
 
 U. S. Geological survey. 
 Bulletins. 
 
 | no. 254. Lindgren, W. Report of progress in the geo- 
 logical resurvey of the Cripple Creek district, 
 Colo.; by W. Lindgren and F. L. Ransome. 
 1904. 
 
 U. S. Dept. of the Interior. 
 
 see also 
 U. S. Geological survey. 
 
 Bull. 254 04 4