.3 
 
COLORADO. 
 
of 
 
 COLORADO. 
 
 J. S. l 
 
 GEORGETOWN, COLO. 
 
 GEORGETOWN COURIER PRINT. 
 
 1887. 
 
3 
 
Bancroft Library 
 
 INTRODUCTORY. 
 
 In the preparation of this glossary, the compiler has depended largely 
 upon the works of J. D. DANA for a description of the mineral species, except 
 in cases where the local mineral has undergone examination. He has also 
 obtained much valuable information from papers upon particular minerals, 
 read before scientific associations, and from articles prepared for the scientific 
 press. 
 
 From a mineralogical point of view the wealth of Colorado exceeds that of 
 the other States. In the metallic minerals almost every variety has been 
 found here. And doubtless many interesting minerals have been overlooked 
 from causes that it is impossible to guard against. The immense size of the 
 mineral region, the exceedingly superficial examination, the vast area yet 
 unexplored, and the absence of scientific knowledge on the part of those whose 
 discoveries were only prompted by the unusual appearance of minerals, have 
 led to overlooking many that are of value to the scientist and commerce. 
 
 Many minerals given are common to several localities in the State, but, 
 as observed, non-exploration has prevented a complete knowledge of their 
 locations. To make subsequent editions of this work more complete, the com- 
 piler solicits the aid of the reader. Any information regarding localities of 
 minerals will be greatly appreciated, and where tht variety of a mineral is 
 in doubt, specimens sent will be investigated. 
 
 The compiler is under special obligations to Mr. WHITMAN CROSS and 
 Mr. W. B. SMITH, of the U. S. Geological Survey, for valuable information. 
 
 The following are titles of the works referred to in the following pages : 
 
 Proceedings of the Colorado Scientific Society. 
 
 Proceedings of the Academy of Natural Science, Philadelphia. 
 
 Proceedings of the American Philosophical Society, Philadelphia. 
 
 American Journal of Science. 
 
 American Chemical Journal. 
 
 Bulletins of the U. S. Geological Survey. 
 
 J. S. RANDALL. 
 
 GEORGETOWN, COLORADO, 
 January, 1887. 
 
MINERALS OF SOLORADO, 
 
 GOLD. 
 
 Crystallizes in the Isometric system ; the octahedron and dodecahedron 
 are the most common forms ; sometimes in cubes and trapezohedrons ; 
 the crystals are usually small and imperfect, and sometimes elongated ; 
 also reticulated, arborescent and spongiform shapes, in scales and rolled 
 masses. Color various shades of gold-yellow, sometimes inclining to sil- 
 ver-white. Very ductile and malleable. Hardness 2*5 to 3. Specific grav- 
 ity 19'34 when quite pure. 
 
 Occurs in greater or less quantities throughout the moun- 
 tainous portions, of the State in the gravel of streams and in 
 veins. The veins of Gilpin County are especially noteworthy 
 for the amount of gold mined annually. Small but unique 
 crystals have been found in a number of the mines. Large 
 masses of wire and leaf gold were taken from the Printer 
 Boy mine, in Lake County, in 1870. In combination with 
 tellurium in many of the mines in Boulder County. 
 
 SILVER. 
 
 Isometric ; occurs crystallized in cubes, octahedrons, trapezohedrons and 
 other forms, but generally distorted ; usually filiform, arberescent, in 
 plates or coatings and sometimes massive. Color silver-white, but subject 
 to tarnish. Ductile. Hardness 2'5-3. Gravity 10'5 when pure. 
 
 Found native in small quantities in nearly all silver mines 
 in the State. In scales, arborescent and filiform, the threads 
 sometimes knotting a mass two inches in diameter, in the 
 mines of Georgetown. Occasionally found in nuggets from 
 the size of a pea to those weighing a pound. The Boulder 
 Nest mine in Clear Creek County, and the Caribou mine in 
 Boulder County were especially productive of native silver in 
 their surface workings. Frequently found in the Blue 
 Kiver placers. Crystals are very seldom met with. 
 
 MERCURY. Quicksilver. 
 
 Isometric ; Occurs in small fluid globules. Color tin-white. Lustre me- 
 tallic. 
 
 Has been found sparingly in the tellurium-bearing mines 
 of Boulder County. 
 
6 Minerals of Colorado. 
 
 NATIVE COPPER. 
 
 Isometric ; occurs crystallized in numerous and often compound forms ; 
 often filiform and arborescent ; also massive. Color copper-red. Streak 
 metallic shining. Ductile and malleable. H. 2'5-3. G. 8'94. Usually 
 found alloyed with some copper, bismuth, etc. 
 
 At the head of Hand-Cart Gulch, where it was mined in 
 early days under the supposition that it was gold. Occurs in 
 small quantities in the mines of Central City. Quite large 
 quantities of wire copper have heen found iu the Pittsburg 
 mine at Empire. Dendritic coatings found in the Centennial 
 mine, Georgetown. Loose masses have been found in the 
 soil near Idaho Springs. Quite abundant in the copper lodes 
 near Golden, where it occurs in seams from J to one inch in 
 thickness. 
 
 NATIVE BISMUTH. 
 
 Hexagonal ; occurs in rhombohedrons nearly approaching the cube ; also 
 reticulated and arborescent shapes ; foliated and granular. Color silver- 
 white with a reddish tinge, but subject to tarnish. Cleavable. Sectile. 
 Brittle when cold, but somewhat malleable when heated. H. 2-2*5. G. 
 9-72. 
 
 Small nuggets of native bismuth are frequently found in 
 the placers of French Gulch, Summit county. Occasionally 
 found in the Las Animas mine, Boulder county, associated 
 with bismutite and bismuthinite. Specimens in collection of 
 J. S. Randall. Bismuth is used extensively in the arts and 
 in medicine; with antimony in the construction of the most 
 sensitive thermometers; with mercury for silvering glass; the 
 sub-nitrate is used for enameling porcelain, and in gilding; 
 in the manufacture of porcelain and optical glass ; the nitrate 
 is used in dyeing lilac and violet in calico printing. 
 
 NATIVE TEULURIUM. 
 
 Hexagonal; occurs in six-sided prisms with the terminal edges re- 
 placed by single planes; generally massive and granular. Color tin- 
 white. Lustre metallic. H. 2-2'5. G. 6'l-6'3. Usually carries some 
 gold. 
 
 Found in the mines of Boulder county, associated with 
 other tellurium minerals. A few crystals have been found 
 nearly an inch long. Specimens in compiler's collection. 
 Tellurium has no use in the arts, and is valuable only for its 
 gold and silver contents. 
 
 NATIVE SULPHUR. 
 
 Orthorhombic ; the prevailing form of crystal is an acute octahedron, com- 
 posed of two four-sided pyramids with rhombic bases; usually occurs in 
 masses, sometimes consisting of concentric coats. Color sulphur-yellow, 
 sometimes reddish or brown. Lustre resinous. Transparent to subtrans- 
 , lucent. H. 1-5-2-5. G. 2 ; 072. 
 
 Abundant about the mud volcanoes in the southwestern 
 part of the State. 
 
Minerals of Colorado. 8 
 
 JAROSITE. Sulphate of Iron. G. A. Konig, Proc. Acad. Nat. Sci.,Phila. 
 Khombehedral ; occurs in crystals ; also massive granular, fibrous, as nod- 
 ules and as an incrustation. H. 2'5. G. 3'5. Color ochre-yellow, amber- 
 yellow to dark brown. Lustre resinous to adamantine. Analysis by Konig 
 of mineral from Iron Arrow mine: sulphuric acid 28'57, sesquioxyd of 
 iron 51'10, water 10'26, potassa 7'13, and a little soda and silica. 
 
 Found in minute brilliant crystals in the Iron Arrow mine, 
 Chaffee county. 
 
 ANGUESIXE. Sulphate of Lead. 
 
 Orthorhombic ; occurs in rhombic prisms which assume the general form 
 of the octahedron when short; often in slender implanted crystals; also 
 occurs massive; lamellar or granular. Color gray, white, yellowish or 
 slightly green. Lustre adamantine, inclining to resinous. Transparent to 
 opaque. H. 3. G. 6. Comp., oxide of lead 73'6, sulphuric acid 26'4. 
 
 In the Freeland mine, Clear Creek county, in aggregations 
 of grayish translucent crystals about the size of a grain of 
 wheat. In many of the Leadville mines in small crystals and 
 in crystalline masses. A product of the decomposition of 
 galena. 
 
 ISICCOWTB. Arsenical Nickel. 
 
 Hexagonal ; rarely occurs crystallized ; usually massive, sometimes reni- 
 form with a columnar structure. H. 5-5'5. G. 7'33-7'67. Lustre metallic. 
 Color pale copper-red, with a gray or black tarnish. Streak pale brown- 
 ish-black. Comp., arsenic 55*9, nickel 44*1. 
 
 Gem mine, on Pine Creek, Fremont county, associated 
 with bornite and pyritiferous minerals, in dolomite gangue. 
 Produces annabergite on alteration (Cross). In the mines at 
 Silver Cliff (G en th). Sparingly in the Rosa mine,atL)umont, 
 Clear Creek county. 
 
 ]tlBI*O*?ITK* Tellnride of Nickel. _ W. F. Hillebrand, Proc. Cbl.Sc.Soc. 
 
 Hexagonal ; generally occurs in indistinct granular and foliated par- 
 ticles. Lustre metallic. Color reddish-white, rarely tarnished brown. 
 Comp., tellurium 76'49, nickel 23'51. 
 
 Occurs in the Forlorn Hope mine, Boulder county, in crys- 
 talline forms, associated with other tellurides. Specimens 
 in collection of Colorado Scientific Society. A rare mineral, 
 heretofore found only in California. 
 
 PHBNACITB. Silicate of Glucina. W. Cross, Am. Jr. Sc., Oct., 1882. 
 
 Rhombohedral ; crystals occasionally oblong, but generally obtuse. Color- 
 less or bright wine-yellow inclining to red ; lustre vitreous ; transpa- 
 rent to opaque ; double-refracting. H. 7'5-8. G. 3. Comp., silica 54'2, 
 glucina 45'8. Resembles quartz. 
 
 At Crystal Park, El Paso county, in cavities in granite, 
 with topaz, zircon, microcline, albite, smoky quartz and li- 
 monite in large, broken crystals. At Florissant in small, flat 
 crystals upon amazonstone with albite, gothite and smoky 
 quartz. Specimens in collection of "Whitman Cross, Denver. 
 
Minerals of Colorado. 
 
 Arsenide of Cobalt. W. M. lies, Am. Jr. Sc., May, 1882. 
 Isometric; occurs in octahedrons, cubes and their modifications; also 
 massive and in imitative shapes. Color tin-white, inclining to steel-gray 
 when massive, sometimes iridescent. Lustre metallic. H. 5'5-6. G' 6'4 
 to 7*2. Analysis of Colorado mineral by lies : cobalt 1T59, iron 11*99, 
 arsenic 63*82, with traces of lead, bismuth and sulphur. 
 
 Abundant in veins near Gothic, Gunnison County, associ- 
 ated with erythrite, native silver, pyrite and calcite. Pro- 
 duces erythrite by alteration. 
 
 A1,ASKAITE. (new). Sulphide of Bismuth, Lead and Silver. G. A. 
 
 Konig, Am. Phil. Soc. Phil., 1881. 
 
 Massive, small foliated, with occasional cleavage planes. Color whitish 
 lead-gray. Lustre metallic. Easily pulverized. G. 6'878. Cornp., sul- 
 phur 17'63, bismuth 56'97, lead 1179, silver 8.74, copper 3'46, antimony 
 0'62, zinc 079. 
 
 Occurs intimately mixed with quartz, barite, chalcopyrite 
 and tetrahedrite at the Alaska mine, Poughkeepsie Gulch. 
 San Juan county. Named after the Alaska mine. 
 
 BEBGERITE. (new.) Sulphide of Lead, Copper and Bismuth. G. A. Ko- 
 
 nig, Am. Chem. Jr., 1881. 
 
 Isometric ; in elongated crystals ; also massive. Cubic cleavage. Color 
 light te dark gray. Lustre brilliant metallic. Comp., sulphur 14'97, bis- 
 muth 20*59, lead 64'23, copper 170. 
 
 From the Baltic lode, near Grant, Park county. Named 
 after Mr. Herman Beeger, of Denver. 
 
 Arsenical Sulphide of Copper and Iron. 
 Isometric ; usually occurs in rhombic dodecahedrons, sometimes variously 
 modified ; also jn cubes and octahedrons, of which the edges and angles 
 are replaced. Color lead-gray to iron-black. Lustre metallic. H. 3'5-4, 
 G. 4'37. Comp., varies, copper 48, sulphur 30, arsenic 13, iron 10. 
 
 Occurs in the Freeland mine, Clear Creek county, in clus- 
 ters of splendent crystals from J to J an inch in diameter. 
 A few dodecahedrons are met with, but most of the crystals 
 appear complicated. Fine specimens in collection ot com- 
 piler. This is the first known occurrence of the mineral in 
 the United States. 
 
 Antimonial Sulphide of Lead. W. F. Hillebrand, Proc. 
 Col. Sci. Soc., vol. 1. 
 
 Orthorhombic ; crystals regular six-sided prisms terminated by low six- 
 sided pyramids; faces of prisms generally deeply striated longitudinally ; 
 also massive, fibrous and columnar. Resembles stibnite, but is harder and 
 heavier. Color steel-gray. Lustre metallic. H. 3-3'o. G. 5'30-5.35. 
 Analysis of Red Mountain mineral by Hillebrand : antimony 35*00, arse- 
 nic 5'64, lead 3277, copper T22, silver 0'23, sulphur 22'50, and small 
 amounts of iron, soda, etc. 
 
 Occurs massive with apparent crystalline structure, of iron- 
 gray color, in the Brobdignag mine, Red Mountain, San Juan 
 county. This is the first observed occurrence of the mineral 
 in the United States. 
 
Minerals of Colorado. 9 
 
 Copper Pyrites. Sulphuret of Copper and Iron. 
 Tetragonal ; the crystals present the general form of the tetrahedron but 
 are sometimes compound ; usually occurs massive and frequently amor- 
 phous. Color brass-yello\r, often with a variegated taruish, Lustre me- 
 tallic. H. 3-5-4. G. 415. Comp., sulphur 34'9, copper 34*6, iron 30'5. 
 
 Massive, in greater or less quantity, in nearly all mines in 
 the state, and nearly always highly auriferous when found in 
 gold mines, and argentiferous when found in silver mines. 
 That from the mines of Red Elephant Mountain, Clear Creek 
 county, usually carries several hundred ounces of silver in 
 a ton of ore. Fine tetrahedrons, measuring from J to J an 
 inch are found in the Freeland mine, Clear Creek county, but 
 nearly all are incrusted with minute crystals of tennantite. 
 Fine specimens in collection of J. S. Randall. 
 
 BISMUXHIXITE. Bismuth Glance. Sulphide of Bismuth. 
 
 Orthorhombic ; occcurs in acicular prisms, striated longitudinally ; also 
 massive with a foliated or fibrous structure. Color lead-gray inclining to 
 tin-white, with a yellowish or iridescent tarnish. Lustre metallic. H. 2. 
 G. 6-4-716. Comp., sulphur 18'75, bismuth 81'25. 
 
 In working a quartz vein near Guy Hill, Jefferson county, 
 a single "pocket" of bismuthinite was encountered, and sev- 
 eral hundred pounds of the ore taken out. Occurs in stout 
 columnar aggregations in the Las Animas mine, near Gold 
 Hill, Boulder county. In quartz veins on Big Thompson 
 Creek, Larimer county. In small crystals and masses, with 
 a gold-yellow tarnish, in the Little Giant lode, Clear Creek 
 county. Beautiful specimens in collection of compiler. 
 
 Arsenide of Iron. W. F. Hillebrand, Am. Jr. Sc., May, 
 1884 ; Proc. Col. Sc. Soc., vol. I. 
 
 Orthorhombic; occurs in right rhombic prisms, parallel to whose planes it 
 may be cleaved ; also massive, acicular and columnar. H. 5-5"5. G. 6*2, 
 7'43. Color tin-white. Lustre metallic. Analysis of Colorado mineral 
 by Hillebrand : arsenic 71' 18, iron 22'96, cobalt 4'37, sulphur 0'56, bis- 
 muth 0'08, copper 0'39, nickel 0'21. 
 
 In the mines on Teocalli and White Rock Mountains, in 
 Gunnison county, in dense radiate masses, and more rarely in 
 trillings and minute crystals, associated with smaltite, mar- 
 casite, galena, chalcopyrite, pyrargyrite, argentite, proustite 
 and native silver, in a gangue of calcite, siderite and barite. 
 Specimens in collection of Colorado Scientific Society. 
 
 (new}. Arsenical Sulphide of Lead. W. F. Hille- 
 brand, Proc. Col. Sc. Soc., vol. 1. 
 
 Occurs massive of a bluish-gray color and slight metallic lustre. H. 3. 
 G. 5-94. Analysis by Hillebrand : arsenic 13'00, sulphur 19'56, lead 61'63. 
 copper 0'17, silver 0'02, iron 0'88, oxygen 0'55. 
 
 Occurs massive in the Zuni mine, near Silverton, and forms 
 the matrix of zunyite. Named after Franklin Guiterman, 
 who first brought the mineral to notice. 
 
10 Minerals of Colorado. 
 
 R.HODOCHR.OSIXK. Carbonate ef Manganese. 
 
 Rhombohedral ; occurs in saddle-shaped lenticular crystals ; also botry- 
 oidal and massive. H. 3'5-4'5. G. 3'4-3'7. Listre vitreous inclining to 
 pearly. Color shades of rose-red, dark red, brown, gray. Translucent. 
 Structure lamellar. Cornp., carbonic acid 38'6, protoxyd of manganese 61'4. 
 
 In beautiful rose-red translucent single crystals in the 
 Royal Albert and Mountain Monarch veins, Uncompahgre 
 district, Ouray county. In large opaque clusters in the 
 Champion vein, Burrough's Park, Hinsdale county (Cross). 
 In small white radiate bunches upon blue celestite, in the 
 Garden of the Gods (Hillebrand). Some fine clusters of 
 crystals have been found in the Danube mine, near Idaho 
 Springs, Clear Creek county. Specimens in collection of J. 
 S. Randall. 
 
 BR.OCHANTI'TK. Hydrous Sulphate of Copper. Richard Pearce, Proc. 
 
 Col, Sc. Soc., vol. 1. 
 
 Orthorhombic ; Occurs in well-defined tabular and acicular crystals and 
 drusy crusts; crystals vertically striated; also massive, and reniform 
 with a columnar structure. H. 3'5-4. G. 3'78. Color emerald-green to 
 blackish-green. Lustre vitreous. Transparent, translucent. Comp., sul- 
 phuric acid 19'9, protoxide of copper 69, water ll'l. 
 
 Occurs in considerable quantity and very pure, with par- 
 tial development of crystal form, in the Monarch mine, Chaf- 
 fee county. 
 
 FLrUORITE* Fluor Spar. Fluorid of Calcium. 
 
 Isometric ; occurs in cubes, octahedrons, rhombic dodecahedrons and their 
 modifications ; crystals often have their faces made up of small cubes, or 
 cavernous with rectangular cavities ; also massiye, coarse or fine granular. 
 Easily cleaved into the tetrahedron, acute rhombohedron and octahedron. 
 H. 4. G. 3'l-3'25. Color white, grey, and various tints of blue, green, 
 yellow, purple and red. Transparent to opaque. Lustre vitreous, some- 
 times splendent. Fragments heated or rubbed against each other in the 
 dark become luminous. Comp., fluorine 48'7, calcium 51'3. 
 
 Large veins of quite pure purple fluorite have been found 
 on St. Vrains Creek and Jim Creek, Boulder county, but are 
 undeveloped, there being no demand for it at present. On 
 Bear and Cub Creeks, Jefferson county, associated with ga- 
 lena. Clusters of transparent crystals, of green color, are 
 found on Plum Creek, Douglas county. Some very good 
 crystallized specimens are found in the Crystal Mountains, 
 El Paso county, associated with amazonstone, gothite, etc. 
 Massive and crystallized of a deep purple color on Tarryall 
 Creek, South Park. It also occurs sparingly in many of 
 the mines throughout the state. Fluor spar is used as a flux 
 in the reduction of ores, and is the source of hydrofluoric 
 acid for etching glass. In England it is wrought into vases 
 and other articles for ornament. Specimens in collection of 
 J. S. Randall. 
 
Minerals of Colorado. 11 
 
 CR.YO WTB. Fluoride of Sodium and Aluminum. Cross and Hittebrand, 
 
 Am. Jr. Sc., Oct., 1883. 
 
 Orthorhombic ; crystals resemble the cube ; usually occurs massive with a 
 rectangular cleavage. Color usually snow-white, sometimes brown or 
 black; lustre vitreous; translucent but becomes more transparent when 
 immersed in water. Melts in the flame of a candle. H. 2*5. G. 3. Anal- 
 ysis of Colorado mineral by Plillebrand: Fluorine 53*55, sodium 32*40, 
 aluminum 12*90, iron oxide, calcium and water. 
 
 In small masses in quartz and feldspar veins, with astroph- 
 yllite, zircon and columbite, near the toll road at St. Peter's 
 Dome, west of Cheyenne Mountain, El Paso county. Spec- 
 imens of the cryolite groupe of minerals cryolite, pachno- 
 lito, prosopite, thomsenolite and gearksutite in collection of 
 Colorado Scientific Society. Specimens of cryolite in collec- 
 tion of J. S. Randall. Cryolite is used for making soda and 
 soda and alumina salts, and white glass. Produces pachno- 
 lite on alteration. 
 
 Fluoride of Aluminum, Calcium and Sodium. Cross and 
 Hillebrand, Am. Jr. Sc., Oct., 1883. 
 
 Monoclinic ; crystals usually four-sided prisms ; also occurs massive. Col- 
 orless to white or yellowish. Transparent to translucent. Analysis by 
 Hillebrand of Colorado mineral : aluminum 12*36, calcium 18*04, sodium 
 10*25, water 8*05, fluorine 51*30. 
 
 Massive and in small transparent crystals, at St. Peter's 
 Dome, El Paso county. Product of the alteration of cryo- 
 lite. Specimens in collection of compiler. 
 
 Fluoride of Aluminum and Calcium. Cross and Hillebrand, 
 Am. Jr. Sc., Oct., 1883. 
 
 Moncclinic; occurs in minute imbedded crystals. Colorless, white or 
 grayish. H. 4*5. G. 2*89. Analysis of Colorado mineral by Hillebrand, 
 fluorine 35*01, aluminum 23*37, calcium 16*19, magnesium 0*11, sodium 
 0*33, water 12*41, loss as oxygen 12*58. 
 
 At St. Peter's Dome, massive and in small crystals, with 
 other fluorides. 
 
 Fluoride of Aluminum, Calcium and Sodium. 
 Cross and Hillebrand, Am. Jr, Sc., Oct., 1883. 
 
 Monoclinic ; occurs in slender prisms, horizontally striated ; also massive, 
 opal or chalcedony-like. Color white, sometimes reddish. Lustre vit- 
 reous to waxy. Transparent to translucent. H. 2*5-4. G. 2*75. Comp., 
 fluorine 52*2, aluminum 15*0, calcium 15*4, sodium 7*6, water 9*8. 
 
 Found sparingly, mixed with pachnolite, at St. Peter's 
 Dome. 
 
 GBARKSUTIXE. Fluoride of Aluminum, Calcium and Sodium. Cross 
 
 and Hillebrand, Am. Jr. Sc., Oct., 1884. 
 
 Occurs in minute needles and kaolin-like. Color white. Lustre dull. 
 H. 2. Analysis of Colorado mineral by Hillebrand : aluminum 15*31, 
 calcium 22*30, fluorine 42*07, water 15*46, sodium 0*10, potassa 0*04. 
 
 Occurs quite abundant as minute crystals and kaolin-like, 
 at St. Peter's Dome. 
 
12 Minerals of Colorado. 
 
 ORTHOCLtASB. Potash Feldspar. 
 
 Monoclinic ; occurs in modified oblique rhombic prisms ; usually thick 
 often rectangular, and also in modified tables ; also massive, some- 
 times lamellar. Color white, gray and flesh-red common ; also greenish 
 and bluish, when it is called Amazonstone. Lustre vitreous, sometimes 
 pearly on a cleavage face. Cleaves easily into plates, Transparent to 
 subtranslucent. H. 6. G. 2'39-2'62. Corap., silica 64'20, alumina 18'40, 
 potash 16'95. 
 
 The common feldspar of granitic rocks. Fine crystals 
 are abundant in the Lida the Little Queen lode at Kokomo. 
 Specimens in collection of J. S. Kandall. 
 
 MICR.OCL*INK. Feldspar. Variety Orthoclase. 
 
 Color pink and gray. Composition, etc., same as orthoclase. 
 
 Associated with amazonstone, etc., near Florissant, and 
 occurring in the same crystalline forms. 
 
 Green Feldspar. Variety Microcline. 
 Crystallizes in the same system, and has nearly the same composition as 
 orthoclase. Color bluish-green. According to Konig, the the color is due 
 to iron. 
 
 Fine specimens near Florissant, El Paso county, in cavities 
 in granite, associated with smoky quartz, albite, topaz, phe- 
 nacite, fluorite, gothite and columbite. The crystals are often 
 of great size and frequently in groups. Baveno and Carls- 
 bad twin crystals are quite frequent. Fine specimens in 
 the compiler's cabinet. 
 
 AIBrrE. Soda Feldspar. 
 
 Triclinic ; occurs generally in flat twin crystals, which are often re- 
 versed, the one upon the other; also massive, either lamellar or granular, 
 the laminae sometimes divergent ; granular varieties often quite fine. Color 
 varies from milk-white to green or red. Lustre pearly upon a cleavage 
 face. Transparent to opaque. H. 6-7. G. 2'59. Comp., silica 68'6, soda 
 11-8, alumina 19'6. 
 
 Near Florissant with amazonstone, sometimes capping crys- 
 tals of that mineral, but more frequently forming the base or 
 matrix in which the crystals are set. Often in granite rocks. 
 
 PIXCMSTONE. Volcanic Glass. A fused feldspar. 
 
 Occurs massive. Color tints of green, yellow, red, brown and black. Lus- 
 tre pitch-like or glassy. Translucent to opaque. Breaks with a sharp 
 edge. H. 5-6. Comp., either orthoclase, albite or oligoclase. 
 
 Forms a dyke on the north wall of the Colorado Central 
 mine, Georgetown. Found near Del Norte. 
 
 ZUNYIXE. (new.) Silicate of Alumina. W. F. Hillebrand, Proc. Col. Sci. 
 Soc., vol. 1. 
 
 Isometric; occurs in tetrahedral prisms with similar terminations. Col- 
 orless when pure, but often black from impurities. Lustre vitreous. 
 Transparent to opaque. H. 7. G. 2'87. Analysis by Hillebrand : silica 
 silica 24'33, alumina 57'88, lithia 10'89, fluorine 5'61, chlorine 2'91, with 
 traces of iron, soda, etc. 
 
 Occurs in very small crystals imbedded in guitermanite 
 from the Zuni mine near Silverton. JSIamed after that mine. 
 
Minerals of Colorado. 13 
 
 COSAWTK. Sulphide of Lead and Bismuth. W. F. Hillebrand, Am. Jr., 
 
 Sc., May, 1884; Proc. Col. Sc. Soc., vol. 1. 
 
 Crystal apparently rhombic, longitudinally striated. Color lead-gray, 
 grayish-white, pale yellow on exposed surface. Lustre metallic. H. 3'5. 
 Analysii ot mineral from Comstock mine, by Hillebrand : bismuth 42'93. 
 lead 22;49, sulphur 17 '11, silver 8'43, copper 7 '50. 
 
 Occurs in irregular masses, rarely an inch in length, with- 
 out crystalline structure, in the Comstock mine, near Parrott 
 City, La Plata county, associated with pyrite, sphalerite, a 
 telluride and gold in a quartz vein. Massive in the Yankee 
 Girl mine, San Juan county. Specimens in collection of Col- 
 orado Scientific Society, 
 
 AUTUNITE* Lime-Uranite. Phosphate of Uranium and Lime. 
 
 Orthorhombic ; crystals very nearly square and cleavable. Color citron- 
 to sulphur-yellow. Streak yellowish. Translucent. Lustre pearly to ad- 
 amantine. H. 2-2-5. G. 3-05-3-19. Comp., phosphoric acid 15*7, oxyd 
 of uranium 62'7, lime 6'1 7 water 15'5. 
 
 Found in the Peabody lode, near Georgetown, in minute 
 greenish-yellow, tabular crystals. Also in a lode on Chicago 
 Creek, Clear Creek county. 
 
 Arsenical Sulphide of Copper. B. S. Burton, Am. Jr. Sc., 
 Jan., 1868. 
 
 Orthorhombic. Massive, granular or columnar. Cleavage perfect giving 
 a brilliant metallic luster. Color grayish to iron-black. Streak grayish- 
 black, powder having a metallic luster. Brittle. H. 3. G. 4"43. Anal- 
 ysis of Willis Gulch mineral by Burton : sulphur 31'56, copper 47'58, 
 arsenic 17"80, antimony 1"37, iron 1*04. 
 
 Occurs massive and crystallized in the Powers lode, Willis 
 Gulch, Gilpin county. Specimens in the compiler's collection. 
 
 ACAXXHI'TE. Silver Glance under an Orthorhombic form. 
 
 Orthorhombic ; crystals usually slender-pointed prisms. Luster metallic. 
 Color iron-black. Sectile, cutting like lead. Fracture uneven, giving 
 a shining surface. H. 2'5 or under. G. 7'16-7'33. Comp., sulphur 12'9, 
 silver 87 '1. 
 
 Occurs in small crystals in the Little Emma mine, George- 
 town. Specimens in compiler's collection. 
 
 AR.OBKXITE. Silver Glance. Vitreous Silver. Sulphuret of Silver. 
 
 Isometric ; primary form the cube ; also occurs in octahedrons and rhom- 
 bic dodecahedrons; reticulated, dendritic, stalactitic, amorphous and 
 massive. Color blackish lead-gray. Streak shining. Luster metallic. 
 Fracture small sub-conchoidal, uneven. Perfectly sectile, cutting like 
 lead. H. 2-2*5. G. 7'196-7'365. Comp., sulphur 12'9, silver 87;L 
 
 This valuable ore of silver occurs in small quantities in 
 nearly all the silver mines in the state, but is seldom found in 
 masses weighing more than two or three pounds, although 
 frequently found in sufficient quantities to make the ore with 
 which it is associated a high grade silver ore. Very good 
 crystallized specimens are occasionally met with in the 
 Georgetown mines. Specimens in compiler's collection. 
 
14 Minerals of Colorado. 
 
 BI^ACK. Sulphuret of silver in the form of a powder or stain. 
 Of frequent occurrence at the surface of silver-bearing 
 veins. Commonly called "sulphurets." 
 
 CHALCEDONY. Cryptocrystalline variety of Quartz. 
 
 Occurs in matnmillated, botryoidal and stalactitic forms, but never in a 
 crystallized state. Luster like that of wax. Color white, grayish, pale- 
 brown to dark-brown and black, rarely delicate blue. H. 7. G. 2'5-2'8. 
 Cornp., silica, with some opal silica. 
 
 Abundant on the ridge to the left of Willow Creek in Mid- 
 dle Park ; also in the basalt on Corral Creek. Handsome 
 pale blue specimens near the Salt Works in South Park; six 
 miles south of the Salt Works in jasper and semi-opal. Fine 
 specimens in San Luis Park on La Garita, filling cavities of 
 amygdaloid. At Los Pinos Agency, in basalt. At the head 
 of Cherry Creek, pseudomorphous after wood. On the Rio 
 Grande, 15 miles above Loma, large geodes. Blue specimens 
 on the Gunnison above the Grand Canon. Common in the 
 valley of the Gunnison near Grand River. Fine specimens in 
 the compiler's collection. > 
 
 Erubescite. Purple Copper Ore. 
 Isometric ; the crystals are generally cubes of which the solid angles are 
 replaced, and the faces are mostly curvilinear. Usually massive. Color 
 between copper-red and pinchbeck -brown, but it soon acquires an irides- 
 cent tarnish. Streak pale grayish-black. Luster metallic. Brittle. H. 
 3. G. 4-4-5-5. Comp., varies, sulphur 22'11, copper 70'13, iron 7'76. 
 
 A valuable gold-ore in the gold mines, and in some mines 
 is quite abundant. Frequently found in silver-bearing veins, 
 and sometimes becomes a valuable ore of silver. In the com- 
 piler's collection are some very good crystals from Central. 
 
 Cross & Hillebrand, Am. Jr. Sc., June, 1882 ; Bulletin No. 
 20, U. 8. Geo. Sur. 
 
 Rhombohedral ; usually occurs crystallized in obtuse rhombohedrons, and 
 has a rhombohedral cleavage. Color white and reddish. Luster vitre- 
 ous. Transparent to translucent. H. 4-5. G. 2'08-2'19. Analysis of 
 Golden mineral by Hillebrand : silica 47'18, alumina 19'67, potash 0'37, 
 lime 9-74, strontia 9'43, soda (V51, water 25'15. 
 
 Good glassy-white specimens are quite abundant in the 
 amygdaloid of North Table Mountain, Golden. Specimens 
 of all the Table Mountain minerals in the compiler's cabinet. 
 
 SXIUBITK. Radiated Zeolite. Bulletin No. 20, U. S. Geo. Sur. 
 
 Orthorhombic ; usually occurs in prisms of which the edges are replaced, 
 and with four-sided summits ; often in sheaf-like aggregations and in di- 
 verging groups ; also massive, in radiating and broad columnar forms. 
 Color white, sometimes yellow, gray, red or brown. Transparent to trans- 
 lucent. Luster vitreous. Double refracting. H. 3'5-4. G. 2'094r-2'161. 
 Analysis of Golden mineral by Hillebrand : silica 54'67, alumina 16*78, 
 lime 7-98, soda T47, water 19'16. 
 
 Occurs sparingly in small, clear crystals in the amygdaloid 
 of Forth Table Mountain, Golden. 
 
Minerals of Colorado. 15 
 
 I^AUMONTIXK. Cross and Hillebrand, Am. Jr. Sc., Aug., 1882, U. 
 
 Geo. Sur., Bui. 20. 
 
 Monpclinic ; occurs in columnar, radiating and compact crystalline masses, 
 and in separate crystals. Color white or yellowish-white, sometimes red- 
 dish. Luster vitreous to earthy. Transparent to opaque; becoming 
 opaque and sometimes pulverulent on exposure. H. 3*5-4. G. 2*25-2*36. 
 Analysis of Table Mountain mineral by Hillebrand : silica 52*07, alumina 
 21*30, lime H'24, potassa 0*42, soda 0*48, water 14*58. 
 
 Occurs as a reddish-yellow sand-like material, and in com- 
 pact crystalline masses in the cavities of the amygdaloid of 
 North Table Mountain at Golden. 
 
 THOMSONITE. Cross and Hillebrand, Am. Jr. Sc., June, 1882; Bulle- 
 tin No. 20, U. S. Geo. Sur. 
 
 Orlhorhombic ; occurs in right rectangular prisms, with cleavage parallel 
 to its side ; usually massive with a columnar or radiated structure ; also in 
 radiated spherical concretions. Luster vitreous inclining to pearly. Color- 
 less or snow-white ; impure varieties brown. Transparent to translucent. 
 Pyroelectric. H. 5-5*5. G. 2*3-2*4. Analysis of Golden mineral by Hil- 
 lebrand : silica 42*66, alumina 29*25. lime 10*90, soda 4*92, water 12*28. 
 
 Occurs in the amygdaloid of Table Mountains, Golden, in 
 minute rectangular blades, which are placed upon each other 
 like the leaves of a closed fan, and in spherical concretions 
 having a radiated structure. 
 
 ANAI.CITE. Cross and Hillebrand, Am. Jr. Sc., June, 1882 ; Bulletin No. 
 
 20, U. S. Geo. Sur. 
 
 Isometric ; usually occurs in trapezohedrons, or 24-sided crystals ; also 
 massive. Luster vitreous. Transparent to opaque. Colorless, white, oc- 
 casionally grayish, greenish, yellowish or reddish-white. H. 5-5*5. G. 
 2*22-2*29. Analysis of Gold'en mineral by Hillebrand: silica 55*80, 
 alumina 22*45, soda 13*45, water 8*35. 
 
 Occurs in pure white or transparent crystals, and vary in 
 size from small ones to those nearly an inch in diameter, in 
 the amygdaloid of North Table Mountain, Golden. On the 
 eastern side of the mountain, analcite is specially abundant. 
 It is also abundant on South Table Mountain, but the crys- 
 tals are usually quite small. 
 
 APOPHYU/TB. Ooss and Hillebrand, Am. Jr. Sc., August, 1882 ; Bul- 
 letin No. 20, U. S. Geo. Sur. 
 
 Tetragonal ; occurs in right square prisms or octahedrons, which often 
 terminate in a sharp pyrimid ; crystals sometimes nearly cylindrical or 
 barrel-shaped; also massive and lamellar. Cleavage highly perfect to 
 all the planes of the primary form. Color white or grayish, sometimes 
 greenish, yellowish, or reddish. Luster vitreous to pearly. Transparent 
 to opaque. H. 4*5-5. G. 2*3-2*4. Analysis of Golden mineral by Hille- 
 brand: silica 51*89, alumina 1*54, iron 0*13, lime 24*51, potash 3*81, soda 
 0*59, water 16*52, fluorine 1*70. 
 
 Occurs in well-developed crystals of prismatic habit in the 
 amygdaloid of North Table Mountain, Golden. The larger 
 crystals which are occasionally half an inch in diameter, are 
 often of a greenish tinge, and have uneven surfaces and are 
 terminated by a large number of small pyramids. 
 
16 Minerals of Colorado. 
 
 A pearly-white, very finely-foliate substance resembling 
 albin is produced by the alteration of apophyllite, which ac- 
 cording to Hillebrand, consists of silica 67'96, alumina 8-48, 
 iron oxyd 1-04, lime 5'47, magnesia 0-53, potassa 1-23, soda 
 0*74, water 14-55. 
 
 Fibrous Zeolite. ~0ross and Hillebrand, Am. Jr. Sc., August, 
 1882 ; Bulletin No. 20, U.& Qeo. Sur. 
 
 Occurs in long slender crystals, often very delicate ; also in silky fibrous or 
 columnar masses. Luster of crystals vitreous ; of fibrous masses more or 
 less silky. Colorless or white, grayish or yellowish. Fragile. Transpa- 
 rent to translucent. H .5. G. 2'2-2'4. Analysis of Golden mineral by Hil- 
 lebrand : silica 46'17, alumina 26'88, lime 877, soda 6'19, water 12'16. 
 
 Occurs in the amygdaloid of North Table Mountain, Gol- 
 den, in masses composed of exceedingly delicate needles 
 loosely grouped together, and sometimes as a continuous 
 membrane, or like a thick cobweb. 
 
 NATR.O WTE. Needle Zeolite, Cross and Hillebrand, Bulletin No. 20, 
 
 U. S. Geo. Sur. 
 
 Orthorhombic ; crystals usually slender, often acicular ; frequently inter- 
 lacing, divergent, or stellate ; also fibrous, radiating, massive, granular, or 
 compact. Luster vitreous to pearly. Transparent to translucent. Color 
 white or colorless, yellowish, grayish or reddish. H. 5-5'5. G. 2'17-2'25. 
 Analysis of Table Mountain mineral by Hillebrand : silica 43'66, alumina 
 24-89, lime 4'87, soda 14'66, water 8'09. 
 
 Natrolite is the least abundant of the zeolites, and has been 
 found only on the northern part of South Table Mountain, 
 where it appears in delicate prisms sparingly deposited upon 
 analcite or associated with that mineral. It has also been 
 observed upon yellow calcite, chabazite and thomsonite. 
 
 Cross and Hillebrand, Bulletin No. 20, U. S. Geo. Sur. 
 Rhombohedral ; occurs in twin crystals, the faces of which are often stri- 
 ated ; frequently in druses. Colorless, white, grayish, greenish, reddish, 
 yellowish. Luster vitreous. Transparent to translucent. H. 4-4'5. G. 
 2'09-2'16. Analysis of Golden mineral by Hillebrand : silica 4676, 
 alumina 21'91, lime H'12, potassa 0'21, soda 1'34, water 18M35. 
 
 Small white and colorless crystals occur sparingly in the 
 amygdaloid of North Table Mountain, Golden. Associated 
 with the levynite is a fibrous mineral, dull white in color and 
 never showing crystal faces, which is almost identical with 
 the levynite in composition. 
 
 Fibrous Zeolite. Cross and Hillebrand, Bulletin No. 20, U. 
 8. Geo. Sur. 
 
 Monoclinic; occurs in long or short prismatic or acicular crystals ; very 
 often in twins ; also massive with a fibrous or radiating structure. Color- 
 less, snow-white, grayish yellowish, and reddish. Transparent to translu- 
 cent. Luster vitreous, or silky when fibrous. H. 5-5'5. G. 2'16-2'40. 
 Analysis of Golden mineral by Hillebrand: silica 46'03, alumina 25*28, 
 iron oxyd 0'27, lime 1277, soda 1'07, potassa 0'13, water 14'48. 
 
 Occurs sparingly in small cavities in a zone just above that 
 
Minerals of Colorado. 17 
 
 containing a great number of zeolites on North Table Moun- 
 tain, Golden. It appears in small spheres or segments of 
 spheres with a radiate structure, and resembles thomsonite, 
 though easily distinguished by the brilliant white color and 
 satin-like luster. 
 
 Variety of Halloysite. Hydrous Silicate of Alumina. Cross and 
 Hillebrand, Bulletin No. 20, U. S. Geo. Sur. 
 Occurs massive ; clay-like or earthy. Luster somewhat pearly or waxy. 
 Feels greasy. Colors usually dark. H. 1-2. G. l'8-2'4. Analysis of 
 Golden mineral by Hillebrand : silica 4617, alumina 22'03, iron oxyd 
 4'64, lime 2'30, magnesia 2'42, potassa and soda 2'06, water 2O38. 
 
 Occurs in the amygdaloid about the center of South Table 
 Mountain, Golden, as a dark brown clay. Placed in water it 
 falls apart without decrepitation, unlike ordinary bole. The 
 mineral is used as a pigment. 
 
 HUBNER.IXK. Tungstate of Manganese. Cross and Hillebrand, Bulletin 
 
 No. 20, U. S. Geo. Sur.; Proc. Col. Sc. Soc., vol. 1. 
 
 Orthorhombic; usually occurs in columnar masses or foliated. Luster ad- 
 amantine on face of cleayage; elsewhere greasy. Color brownish- red, 
 brownish-black, yellowish. Streak yellowish-brown. Opaque. H. 4'5. 
 G. 7'4. Analysis ot mineral from Koyal Albert vein by Hillebrand : silica 
 0'62, tungstic acid 75'58, protoxyd of manganese 23'40, protoxyd of iron 
 0-24, lime 0'13, columbic acid (?) 0'05. 
 
 The mineral occurs in the Royal Albert vein, Uncompahgre 
 district, Ouray county, in long flattened crystals vertically 
 striated, of a brownish-black to pale yellow color, imbedded 
 in quartz. It is also found near Silverton, and at Jimtown, 
 Boulder county, where it appears in small blades disseminated 
 through quartz. Specimens in compiler's cabinet. 
 
 HEX1OXROPB. Bloodstone. Cryptocrystalline Quartz. 
 
 A bright to leek-green variety of chalcedony or jasper, with small spots of 
 red jasper looking like drops of blood. 
 
 Occurs in a vein of jasper in the hill at the junction of Wil- 
 low Creek and the Grand River, Middle Park. On account 
 of its beautiful color, heliotrope has always been much used 
 for rings, seals and other ornaments. Specimens of the diff- 
 ferent forms of quartz in the compiler's cabinet. 
 
 Cryptocrystalline Quartz. 
 A variety of chalcedony (p. 14) of a clear bright red tint, pale to deep in 
 shade. The brownish-red is also called carnelian. The color is due to the 
 presence of iron. 
 
 Found sparingly on the ridge to the left of "Willow Creek 
 in Middle Park; on the Rio Grande near Loma; near Lark- 
 spur; on Cherry, Kiowa and Running Creeks, pseudomorph- 
 ous after wood. From the high polish of which it is suscept- 
 ible, and its bright colors, carnelian has always, in both an- 
 cient and modern times, been much used for ornaments. 
 
18 Minerals of Colorado. 
 
 PRASE* Cryptocrystalline Quartz. 
 
 A translucent leek-green chalcedony (p. 14). 
 
 Occasionally found in San Luis Park. 
 
 CHRYSOPRASE. Cryptocrystalline Quartz. 
 
 An apple-green chalcedony (p. 14), the color of which is due to the pres- 
 ence of nickel. 
 
 Occurs sparingly on La Garita, west of San Luis Park. In 
 geodes in Middle Park. 
 
 BAIMDED AGATE. Fortification Agate. Eye Agate. Clouded Agate. 
 A variegated chalcedony. The colors are either banded or in clouds. The 
 bands are delicate parallel lines of various shades of color. They follow 
 waving or zigzag courses, and are occasionally concentric circular, when it 
 it is called eye agate. When the colors are irregular it is called clouded 
 agate. 
 
 Banded and clouded agates are occasionally found on Wil- 
 low Creek in Middle Park ; near the Salt Works in South 
 Park; near the source of Cherry Creek ; ten miles south of 
 Canon City, in sandstone; on the La Garita, south of San 
 Luis Park; large geodes on the Rio Grande, 15 miles above 
 Loma. Owing to its beauty, variety, hardness and capability 
 of receiving a high polish, agate is much used both in articles 
 of utility and ornament. 
 
 MOSS AGATE. Mocha Stone. 
 
 A chalcedony filled with brown, black, green or red moss-like or dendritic 
 forms. 
 
 Abundant on Williams Fork, Middle Park; in South Park 
 between Fairplay and the Salt Works. 
 
 AGATIZEO WOOD. 
 
 Wood petrified with clouded agate. 
 
 Middle Park near Hot Spring, and on the right of Willow 
 Creek; around the Salt Works in South Park; abundant 
 near the sources of Cherry, Kiowa and Bijou Creeks. 
 
 OXYX. 
 
 Like agate in consisting of layers, but the layers are in even planes and 
 usually thicker. The colors are generally of a light brown and an opaque 
 white. 
 
 Occurs sparingly on the ridge to the left of Willow Creek, 
 in Middle Park, and also near Grand Lake; on the La Garita, 
 west of San Luis Park; a variety called chalcedonyx is found 
 in San Luis Park. Eextensively used for cameos and other 
 articles of adornment. 
 
 SARDOXYX. 
 
 Those varieties of onyx which are composed of alternate layers of red and 
 white. 
 
 A few specimens have been found in the Willow Creek 
 region, Middle Park. It is the most beautiful, the rarest and 
 most valuable form of onyx. 
 
Minerals of Colorado. 19 
 
 PYRARGYIMXB. Kuby Silver. Dark Bed Silver Ore. 
 
 Rhombohedral ; crystals usually prismatic ; generally occurs in small 
 masses. Lustre metallic-adamantine. Color black, approaching coch- 
 ineal-red. Streak cochineal-red. Translucent-opaque. H. 2-2*5. G. 5'7, 
 Comp., sulphur 177, antimony 22'5, silver 59'8. 
 
 Occurs in small masses in most of the silver mines in the 
 state, but rarely found crystallized. Specimens in compiler's 
 collection. 
 
 PR.OUST1XB. Light Kuby Silver Ore. 
 
 Rhombohedral ; occurs in granular masses and in small crystals. Lustre 
 adamantine. Color cochineal-red. Streak cochineal-red, sometimes in- 
 clined to aurora-red. Subtransparent subtranslucent. H. 2.-2'5. G. 
 5'42-5'56. Comp., sulphur 19'4, arsenic 15'2, silver 65'4. 
 
 Occurs in the mines of Geneva District and about Monte- 
 zuma in small masses and in clusters of minute crystals. In 
 the Colorado Central mine, Georgetown, in beautiful crystals 
 and massive, associated with galena, sphalerite and crystals 
 of polybasite. Compiler's collection. 
 
 Indigo Copper Ore. 
 Hexagonal, but rarely occurs in crystals ; commonly massive or spheroidal. 
 Color indigo-blue or darker. Streak lead-gray to black, shining. Lustre 
 of crystals submetallic ; dull when massive. H. l'5-2. G. 4'59. Comp., 
 sulphur 33'5, copper 66'5. 
 
 Occurs in small grains in the Pewabic lode, Central City. 
 In the form of a powder in some of the mines of Cascade and 
 Daily Districts, Clear Creek County. 
 
 COI^UMBIXB. Columbate of Iron. Ore of Columbium. J. L. Smith, 
 
 Am. Jour. Sc., May, 1877. 
 
 Orthorhombic ; occurs in single crystals, crystalline masses, rarely massive. 
 Lustre submetallic; a little shining. Color iron-black, brownish-black, 
 grayish-black ; often iridescent. Streak dark red to black. Fracture sub- 
 conchoidal, uneven. H. 6. G. 5 4-6'5. Analysis, Colorado mineral, by 
 J. L. Smith : columbic acid 79'61, iron protoxide 14*14, manganese pro- 
 toxide 4'61, loss by heat '50. 
 
 In the Pike's Peak region, in small black acicular crystals 
 imbedded in amazonstone. A few large single crystals and 
 fragments have been also been found. Compiler's collection. 
 
 Cross and HUlebrand, Bui. No. 20, U. S. Geo. Sur. 
 Isometric; in cubes and octahedrons. Colorless. Transparent. H. 4*5. 
 G. 2'4. Comp., alumina 22'94, fluorine 5O05, calcium T99, magnesia 5'52, 
 sodium 4'66, water 14'84, 
 
 Occurs in minute crystals in cavities in thomsenolite and 
 pachnolite, at St, Peter's Dome, El Paso County. The crys- 
 tals here found are transparent cubes whose corners are' re- 
 placed by small octahedron faces and seldom reach a diam- 
 eter of 1 MM . Some crystals of pachnolite seem to be coated by 
 a crystalline dust whose particles are found under the micro- 
 scope to be most perfect little crystals of ralstonite. 
 
20 Minerals of Colorado. 
 
 BIvP ASOMTBi i (new.) Cross awd Hillebrand, Bui No. 20, Z7. & Geo. SJw* 
 
 n ^lm. Jr. Sc., October, 1883. 
 
 Probably , isometric ; crystals faces cube and octahedron. Colorless, but 
 not perfectly clear. Calculated analysis by Hillebrand: alumina 11'32, 
 calcium 0'72, magnesia G'22^ potassium 28'94, sodium 9'90, fluorine 46'98. 
 
 Sparingly as a compact irregular mass iu cavities in mass- 
 ive pachnolite from St, Peter's Dome, El Paso County, from 
 which it was named. 
 
 ZIRCON. Ooss and Hillebrand, Am. J. Sc., Oct., 1882 ; Konig, Am. Phi. Soc. 
 
 xvi, 518, 1877. 
 
 Tetragonal ; primary form an obtuse octahedron with a square base ; also 
 occurs in irregular forms and grains. Lustre adamantine. Colorless, pale 
 yellowish, grayish, yellowish-green, brownish-yellow, reddish-brown. 
 Transparent to ; opaque. Fracture conchoidal and brilliant. Double re- 
 fraction strong, positive. H. 7;5. G. 4'5-4'75. Comp., silica 33, zirconia 
 67. Konig made an analysis of zircon from the Pike's Peak region, which 
 was published in the Proceedings of the American Philosophical Society 
 of Philadelphia, in, 1.877. 
 
 Found in numerous localities in the Pike's Peak region, 
 associated with astrophyllite, amazon stone, etc. Near the 
 Pike's Peak toll-road, about due west from Cheyenne Moun- 
 tain, a prospect tunnel, in following a vein-like mass of white 
 quartz in granite, disclosed zircon imbedded in the quartz so 
 abundant that a cubic inch of the latter mineral contains from 
 25 to 100 crystals and particles' of zircon, varying in size from 
 I downward. Some of these crystals are very perfect, but 
 exhibit only the pyramid, the prisim entirely lacking. Many 
 of them are beautifully clear and of deep reddish-brown, pink, 
 pale honey-yellow and occasionally deep emerald-green color. 
 The perfection of these crystals, with their transparency and 
 color, make them among the most beautiful known. Small 
 irregularly shaped zircons and occacionally elongated crystals 
 occur in the sands of Bear Kiver. They are of various shades 
 of brown, red and yellow, and many are colorless. Most of 
 them are transparent and qujte brilliant, but too small to be 
 cut for setting. Specimens from both the above localities in 
 the compiler's cabinet. Although the zircon is but rarely 
 used in jewelry, it makes a beautiful gem when of good color 
 and has a peculiar opalescent reflection. 
 
 Magnesia Alum. Goldsmith, Proc. Acad. Nat. Sci. 
 1876. 
 
 In fine acicular crystals ; long fibrous masses ; and efflorescences. Lustre 
 silky. Color white or yellowish. Becomes pulverulent and white on ex- 
 posure. Taste hitter astringent. H. 1. Analysis of Monument Park 
 mineral by Goldsmith : sulphuric acid 38'69, alumina 1T90, magnesia 4'89, 
 potassa-and soda 0'68, sand 1'90, water, by difference, 41'94. 
 
 Occurs crystallized in thin needles in the region of Monu- 
 ment Park. 
 
Minerals of Colorado. 21 
 
 AI^TAITE. Telluride of Lead. Genth, Am. Phi. Soc., 1874. 
 
 Isometric; usu?lly massive; rarely in cubes. Cleavage cubic.- Lustre 
 metallic. Color tin-white, resembling that of native antimony, with a yel- 
 low tarnish, Sectile. H. 3-3'5. G. 8'159. Analysis by Genth of mineral 
 from the Red Cloud mine, Boulder county: quartz 0'19, gold O'l 9, silver 
 0'62, copper 0'06, lead 60'22, zinc 9'15, iron 0'48, tellurium 37'99. 
 
 Occurs in a number of the tellurium-bearing mines at Gold 
 Hill, Boulder County. Fine crystals in the Slide mine. 
 
 CASSITERTXE. Tin-Stone. Oxyd of Tin. Cross and Hillebrand, Bui. 
 
 20, U. S. Geo. Sur. 
 
 Tetragonal ; primary form an obtuse pyramid with a square base ; it is 
 found in quadrangular prisms, terminated by four-sided pyramids, and in 
 many more complex forms; often in reniform shapes. Structure fibrous 
 divergent ; also massive, granular or impalpable. Lustre adamantine, and 
 crystals usually splendent. Color brown or black ; sometimes red, gray, 
 white or yellow. Streak white, grayish, brownish. Nearly transparent to 
 opaque. H. 6-7, G. 6'4-7'l. Comp., tin 78-67, oxygen 21'33. 
 
 Occurs in small crystalline masses imbedded in albite and 
 quartz on Devil's Head Mountain, Douglas County, associated 
 with topaz, amazonstone, smoky quartz and fluor spar. 
 With amazonstone at Florissant. 
 
 Cerium-Epidote. Iddings and Cross, Am. Jr. Sc., Aug., 1885. 
 Monoclinic ; isomorphous with epidote ; crystals either short, flat tabular, 
 or long and slender, sometimes acicular ; twins like those of epidote ; also 
 massive and in angular and rounded grains. Lustre submetallic, pitchy 
 or resinous occasionally vitreous. Color pitch-brown to black, either 
 brownish, greenish, grayish or yellowish. Streak gray, sometimes slightly 
 greenish or brownish. Subtranslucent to opaque. Fracture uneven or 
 subconchoidal. Double refraction either distinct or wanting. H. 5'5-6. 
 G. 3'9-4'2. Comp., silica 33, alumina 15, protoxide of iron 15, cerium 21, 
 lime 11, lanthanium, didymium, yttria, manganese, etc. 
 
 Forms an accessory constituent of the biotite porphyrite of 
 Ten-Mile District, Summit County, in which the crystals oc- 
 cur of a brilliant black color and oily lustre. In the porphy- 
 rite of Mount Silverheels, Park County, of a chestnut-brown 
 color. In the gneiss of the Medicine Bow Range, the quartz 
 porphyry of the Mosquito Range, and on Eagle River. 
 
 Hydrous Silicate of Alumina. Konig, Proc. Acad. Nat. 
 Sci. Phila., 1876. 
 
 Amorphous; usually in thin incrustations, with mammillary surface; 
 sometimes stalactitic; occasionally almost pulverulent. Lustre vitreous 
 to subresinous ; bright and waxy internally. Color pale sky-blue, some- 
 times greenish to deep green, brown, yellow or colorless. Streak uncol- 
 ored. Translucent. Fracture imperfectly conchoidal and shining to 
 earthy. Very brittle. Adheres to the tongue. H. 3. G. 1*85. Comp., 
 silica 22, alumina 33, water 41. An analysis by Genth of what was sup- 
 posed to be chrysocolla, from Bergen Park, gave 33.85 alumina, and 5'40 
 of copper oxide, which corresponds to allophane and chrysocolla in the 
 ratio of 5:1. 
 
 Forms a thin bluish crust on limonite near Bergen ranch, 
 Jefferson County. 
 
22 Minerals of Colorado. 
 
 Soda Hornblende. Konig, Am. Phi. Soc., 1877. 
 Probably ruonoclinic; occurs in crystals and cleavable masses. Color 
 pure black; in thin scales deep green to brown. Streak grayish-green. 
 H. 6. G. 3'44. Comp., silica 50'5, sesquioxyd of iron 26'9, protoxyd of 
 iron 12'1, soda 10'5. Analysis of El Paso County mineral by Konig was 
 published in the proceedings of the American Philosophical Society of 
 Philadelphia. 
 
 Occurs at St. Peter's Dome, El Paso County, with astroph- 
 yllite, zircon, etc. 
 
 GAHXITB. Zinc-Spinel. Oenth, Am. Phi. Soc. 
 
 Isometric; occurs in octahedrons and dodecahedrons. Lustre vitreous or 
 somewhat greasy. Color dark green. grayish -green, deep leek-green, green- 
 ish-black, bluish, black, yellowish, grayish-brown. Subtranslucent to 
 opaque. H. 7'5-8. G. 4-4-6. Comp., alumina 61'3, oxyd of zinc 38*7. 
 
 Large rough crystals occur in the Cotopaxi mine, Chaftee 
 County. 
 
 TOPAZ. Cross and Hittebrand, Am. Jr. Sc., Oct., 1882; Bui. 20, U. 8. Geo. 
 
 Sur. W. B. Smith, Bui. U. S. Geo. Sur. 
 
 Orthorhombic ; primary form right rhombic prism; crystals usually hemi- 
 hedral, the extremes being unlike. Cleavage perfect at right angles to the 
 principal axis ; also occurs fine columnar, granular, coarse or fine. Lustre 
 vitreous. Color straw-yellow, wine-yellow, white, grayish, greenish, blu- 
 ish, reddish. Transparent to subtranslucent. Pyroelectric. H. 8. G. 
 3*4-3*65. Analysis of Florissant specimen by Hillebrand : silica 33'15, 
 alumina 57'01, fluorine 16'04, oxygen for fluorine 6*75. 
 
 Found in Crystal Park, south of Manitou, in cavities in 
 granite containing feldspars, smoky quartz, zircon and phena- 
 cite; at the main amazonstone locality near Florissant : and, 
 more plentifully and in better form than elsewhere, on Devil's 
 Head Mountain, Douglas County. In small crystals in the 
 nevadite from Chalk Mountain, where Lake, Eagle and Sum- 
 mit Counties join. A fragment of a crystal 3J in. in its long- 
 est diameter, was found near Florissant, which evidently 
 came from a crystal about one foot in diameter. It is clear 
 in parts and has a decided greenish tinge. It was supposed 
 to be fluor spar by the original collectors, and the other pieces 
 of the crystal are undoubtedly lost. Crystals are also found 
 in this locality deposited upon or partially imbedded in am- 
 azonstone, albite, etc. In size the crystals vary from a length 
 of nearly two inches to those which are almost microscopic. 
 Some of the crystals have a decided greenish tinge, although 
 many are colorless. The topaz found at Devil's Head Moun- 
 tain also occur in cavities with amazonstone, smoky quartz, 
 and other minerals, and are the most noteworthy crystallized 
 species, some of the specimens found being probably the best 
 yet discovered in the United States. Much of the topaz is 
 reddish, though wine-yellow, milk-blue, and colorless crystals 
 are found. Quite perfect and clear crystals have been found 
 weighing from five to six ounces. 
 
Minerals of Colorado. 23 
 
 KAL,IN1TK. Potash Alum. Native Alum. 
 
 Isometric ; usually fibrous or massive, or in inealy or solid crusts. Lustre 
 vitreous. Color white. Transparent translucent. H. 2-2'5. G. 1'75. 
 Comp., sulphate of potash 18*4, sulphate of alumina 36'2, water 45'5 
 
 Occurs as an efflorescence on argellaceous rocks at Canon 
 City, on Turkey Creek, Little Thompson Creek, and in small 
 quantities in various localities along the "hog-back. " 
 
 STIBNITE. Antimony Glance. Sulphuret of Antimony. 
 
 Orthorhombic ; primary form a right rhombic prism ; occurs crystallized 
 in variously modified and terminated rhombic prisms, which are some- 
 times closely aggregated laterally ; lateral planes of crystals deeply stri- 
 ated longitudinally ; also occurs columnar, coarse or fine; also granular to 
 impalpable. Color and streak lead-gray ; inclining to steel-gray; subject 
 to blackish tarnish. Lustre metallic. Sectile. Thin lamina a little flex- 
 ible. H. 2. G. 4-51-4-62. Comp., sulphur 28*2, antimony 71'8. 
 
 Occurs crystallized in the North Star mine, Sultan Moun- 
 tain, near Silverton. 
 
 QUARTZ. 
 
 Rhombohedral ; occurs in hexagonal prisms, sometimes terminated at both 
 ends by six-sided pyramids. Colorless when pure ; various shades of yel- 
 low, red, brown, green, blue, violet and black. Transparent to opaque. 
 Lustre vitreous, sometimes inclining to resinous. Fracture conchoidal. 
 Tough, brittle, friable. H. 7. G. 2'5-2"8. Comp., pure silica, or, oxygen 
 53-33, silicon 46 '67. 
 
 Quartz is a constituent of many rocks, and composes most 
 of the pebbles of gravel beds. It takes on more forms and 
 colors than any other mineral, and is divided into three va- 
 rieties, the vitreous, chalcedonic and jaspery. Vitreous vari- 
 eties are distinguished by their glassy fracture ; chalcedonic 
 varieties by having a subvitreous or waxy lustre, and gener- 
 ally translucent ; the jaspery varieties are opaque. 
 
 ROCK CRYSTAL. 
 
 Pure pellucid quartz. Usually occurs in six-sided crystals. 
 
 Clear crystals, some of which are doubly terminated, are 
 found near Maysville. Large crystals in the Blk mountains. 
 Pellucid water- worn nodules in the gravel of Platte River. 
 Common as drusy incrustations in the mines. Rock crystal 
 is made into lenses for spectacles, and is known as Scotch and 
 Brazilian Pebbles. The so-called Alaska and California dia- 
 monds are cut from rock crystal. 
 
 AMETHYST. 
 
 Quartz of a clear purple or violet-blue color, of various degrees of intensity. 
 The color is supposed to be derived from manganese. 
 
 Fine specimens have been met with in the veins near Du- 
 mont. Small crystals at Nevada and Black Hawk. On Grape 
 Creek, Fremont County. In the Elk mountains. In geodes 
 on the Rio Grande River. Occasionally in South Park, asso- 
 ciated with smoky quartz, amazonstone and gothite. 
 
24 Minerals of Colorado. 
 
 ROSE QUARTS. 
 
 A transparent, or nearly transparent variety of quartz, of a rose-red or 
 pink color. It usually occurs massive, and often much fractured. 
 
 Occuas in large masses at the summit of Floyd Hill ; near 
 Central City; on Bear and Soda Creeks. 
 
 QUARTZ. False Topaz. Citrine. 
 Color lemon-yellow, golden, or wine-yellow. 
 
 Found in the gravel on the divide between the Platte and 
 Arkansas, about the head of Plum Creek. On the west slope 
 of Pike's Peak, near its base. 
 
 CAIRNGORM. Smoky Quartz. Morion. 
 
 Color various shades of brown, passing into black. * 
 
 Abundant about Florissant, El Paso County, where it 
 occurs in "pockets" in the granite, associated with amazon- 
 stone, albite, gothite and fluorite. Some of the crystals are 
 of great size and extreme beauty. One crystal was found 
 which measured 4^ feet in length and 10 inches in diameter 
 at the base. A great many have been found from 20 to 30 
 inches in length. The crystals are usually transparent, and 
 have been used quite extensively in the manufacture of jew- 
 elry. Smoky quartz is also found at the head of Plum Creek ; 
 in the neighborhood of Larkspur, Summit and Monument; 
 at the head of Beaver Creek; on Cheyenne mountain; Elk 
 Creek, and in the nevadite of Chalk mountain. 
 
 JASPER. 
 
 Impure opaque colored quartz. The most common colors are brown, red 
 and yellow. Called Ribbon Jasper when the colors are in broad stripes or 
 bands. Egyptian Jasper when the colors appear in zones. 
 
 Red and yellow jasper is found very plentifully in Middle 
 and South Parks. A large proportion of the petrified wood 
 on the Platte and Arkansas divide, is jasper. Along the 
 sources of Cherry, Kiowa, and Bijou Creeks, it is quite com- 
 mon to find large trees, 60 or 70 feet in length, changed to 
 jasper. Ribbon Jasper is found near Larkspur ; also in Mid- 
 dle Park, at the junction of the Willow and Grand, in dark 
 green and yellow stripes. Egyptian Jasper near Larkspur. 
 
 CERARGYRIXE. Horn Silver. Chloride of Silver. 
 
 Isometric; occurs crystallized in small cubes and acicular prisms; gener- 
 ally massive and looking like wax; sometimes columnar, or bent col- 
 umnar; often in crusts. Lustre resinous, passing into adamantine. Color 
 pearl-gray, grayish-green, whitish, rarely violet-blue, colorless sometimes 
 when perfectly pure ; brown or violet-brown on exposure. Streak shining. 
 Transparent feebly translucent. Fracture somewhat conchoidal. Sectile. 
 Comp., Chlorine 247, silver 75'3. 
 
 Common in the mines of Leadville, Silver Cliff and Rosita. 
 Occasionally found near the surface of veins about George- 
 town and elsewhere. 
 
Minerals of Colorado. 25 
 
 CEXESTITE. Fibrous Heavy Spar. Sulphate of Strontia. 
 
 Orthorhombic; in modified rhombic prisms; crystals sometimes flattened; 
 often long and slender; also fibrous and radiated; sometimes globular; 
 occasionally granular. Lustre vitreous, sometimes inclining to pearly. 
 Color white, often bluish, and sometimes reddish. Streak white. Trans- 
 parent subtranslucent. Brittle. Trichroism sometimes very distinct. 
 Phosphoresces when heated. H. 3-3'5. G. 3'92-3-95' Comp., sulphuric 
 acid 43'6, strontia 56'4. 
 
 Occurs as nodules in the Garden of trie Gods, which, upon 
 being broken, present a mass of beautiful blue crystals; occa- 
 sionally in fibrous masses. Celestite is used in the arts for 
 making nitrate of strontia, which is employed for producing 
 a red color in fire works. 
 
 SPHALtKRITK. Blende. Zinc-Blende. Sulphuret of Zinc. 
 
 Isometric; tetrahedral ; occurs crystallized and amorphous; botryoidal 
 and other imitative shapes; sometimes fibrous and radiated ; also massive, 
 compact. Cleavage, dodecahedral, highly perfect. Color brown, yellow, 
 black, red, green ; white or yellow when pure. Lustre resinous to ada- 
 mantine. Streak white to reddish-brown. Transparont to translucent. 
 Fracture conchoidal. Brittle. H. 3'5-4. G. 3'9-4'2. Comp., sulphur 33, 
 zinc 67. 
 
 Common in many of the gold and silver mines, and fre- 
 quently rich in gold or silver, although usually of but small 
 value. Fine cabinet specimens of black blende in the Maine 
 and other mines about Georgetown ; in the Coaley, Calhoun 
 and Delaware lodes, Gilpin County ; beautiful green crystals 
 in the L/ittle Giant lode, near L/awson, Clear Creek County. 
 
 Sulphuret of Molybdena. 
 Hexagonal ; occurs in flat hexagonal tables, with a cleavage parallel to 
 their terminal planes ; generally massive with a foliated structure, or'in 
 scales. Color pure lead-gray. Lustre metallic. Streak similar to color, 
 slightly inclining to green. Laminae flexible, but not elastic. Sectile, and 
 almost malleable. Leaves a gray trace on paper, a greenish trace on por- 
 celain. H. 1-1*5, being easily impressed by the nail. G. 4'4-4'8. Comp., 
 sulphur 41, molybdenum 59. 
 
 About Georgetown ; Rock Creek, Gunnison County ; Boul- 
 der, Gilpin and Summit counties. Salts 'of molybdenum are 
 used to some extent in chemical operations. 
 
 HALITE. Common Salt. Kock Salt. Muriate of Soda. Chlorid of Sodium. 
 Isometric; usually occurs in cubical crystals; rarely in octahedrons; 
 faces of crystals sometimes cavernous. Massive and granular, rarely col- 
 umnar. Cubic cleavage. Lustre vitreous. Color white, sometimes yel- 
 lowish, reddish, bluish, purplish ; often colorless. Transparent translu- 
 cent.* Fracture conchoidal. Rather brittle. Soluble. Taste purely 
 saline. H. 2'5. G. 2'l-2'257. Comp., chlorine 607, sodium 39'3, com- 
 monly mixed with some sulphate of lime, chlorid of calcium, etc. 
 
 Occurs in solution and as an incrustation about the salt 
 springs in South Park. Works were erected about 1868, and 
 considerable salt manufactured, but the company got into lit- 
 igation, and the works were abandoned. 
 
26 Minerals of Colorado. 
 
 GYPSUM. Sulphate of Lime. 
 
 Monoclinic; crystals usually in right rhomboidal prisms, with beveled 
 sides; frequently the shape of an arrow-head ; eminently foliated in one 
 direction, and cleaving easily, affording laminae that are flexible but not 
 elastic; crystallized variety called selenite. Also occurs in laminated 
 masses ; fibrous, with a satin lustre (satin-spar)- in stellated or radiating 
 forms, consisting of narrow laminae; also granular and compact (alabaster). 
 Color usually white; 'sometimes gray, yellow, reddish, brown, black. 
 Streak white. Transparent opaque. H. l'5-2. G. 2'3. Comp., sulphu- 
 ric acid 46'5, lime 32'6, water 20'8. 
 
 Occurs in large beds of great purity in the South Park and 
 along the base of the mountains; specially available at Mor- 
 rison and Colorado Springs, where mills have been built for 
 the manufacture of gypsum into plaster-of-paris. 
 
 SEUENITK. Crystallized variety of Gypsum. 
 
 Occurs either in distinct crystals, or broad folia, the folia sometimes a yard 
 across, and transparent throughout. Cleaves easily, the plates bending in 
 one direction. 
 
 Occurs in grouped and single crystals on Box Elder Creek, 
 Ivaramie County ; at River Bend, on the K. P. Railway, in 
 fine crystals ; on Bear Creek, near Morrison. Selenite, in 
 thin folia, was formerly extensively used in windows, and is 
 still used for that purpose by the Mexicans in the Socorro 
 mountains. 
 
 SATIN SPAR. Fibrous Gypsum. 
 
 Occurs in fine fibrous masses, having a satin lustre, and the pearly opales- 
 cence of the moonstone. 
 
 Fine white masses at Morrison. Pink and white near 
 Quick's ranch, on Plum Creek. Satin Spar is used in the 
 manufacture of beads and other ornamental articles. 
 
 ALABASTER. Granular Gypsum. 
 
 Fine-grained, and either white or delicately shaded. 
 
 On Box Elder Creek, in immense deposits. At Morrison, 
 white and mottled. At Colorado Springs, pink and white. 
 At Canon City, pure white. 
 
 GADOI^INITB. Eakins, Proc. Colo. Sc. Soc., 1885. 
 
 Orthorhombic; in oblique rhombic prism; occurs also in small masses. 
 Color black, greenish-black ; dull externally, internally shining; in thin 
 splinters nearly transparent, and grass-green to olive-green. Streak green- 
 ish-gray. Lustre vitreous. Subtranslucent opaque. Fracture conch- 
 oidal. H. 6'5-7. G. 4-4'5. Analysis of Colorado mineral by Eakins: 
 Silica 22'13, alumina 2'34, protoxyd of iron T13, thoria Q'&9, oxide of 
 cerium ll'lO, oxide of lanthanum and didymium 21/23, erbium 12'74, 
 yttria 9'50, oxide of iron 10'43, beryllium 7'19, lime 0'34, magnesia 0' 14, 
 potassa 0'18, soda 0'28, water 0'86. 
 
 Occurs in small fragments on Devil's Head mountain, 
 Douglas County. This is the first observed occurrence of the 
 mineral in this country, and was found by Mr. W. B. Smith, 
 of the U. S. Geological Survey. 
 
Minerals of Colorado. 27 
 
 Silicate of Zinc. 
 
 Orthorhorabic ; occurs in obtuse rhorabohedrons, and in long quadrilateral 
 tables; also stalactitic, mammilated, botryoidal, fibrous, massive and gran- 
 ular. Lustre subpearly, sometimes adamantine. Color white ; sometimes 
 with a delicate bluish or greenish shade ; also yellowish to brown. Streak 
 white. Transparent translucent. Brittle. Fracture uneven. Pyroelec- 
 tric. Double refraction strong. H. 4'5-5. G. 3'16-3'49. Comp., silica 
 25'0, oxyd of zinc 67'5, water 7'5. 
 
 Occurs as a delicate white incrustation in the mines of 
 Leadville. 
 
 H. F. and H. A. Kellar, Am. Ghent. Jr., vol. 2. 
 Radiated structure. Color dark lead-gray. Lustre bright. Soft. G. 6'29. 
 Analysis of mineral from Lillian Co's mines: sulphur 15'21, bismuth 32'62, 
 lead 43'94, silyer 5*78, copper trace. 
 
 Occurs in the mines of the Lillian company on Printer Boy 
 Hill, near Leadville, in nodules of various sizes up to several 
 feet in diameter, more or less oxidized. The fresh mineral 
 has a fine-grained crystalline structure, and steel-gray color. 
 
 GRAPHITE. Plumbago. Black Lead. 
 
 Hexagonal ; in flat six-sided tables. Commonly in imbedded, foliated, or 
 granular masses. Perfect cleavage. Color iron-black to dark steel-gray. 
 Streak black and shining. Lustre metallic. Soils paper. Sectile ; thin 
 laminae flexible. Feel greasy. H. 1-2. G. 2'0891. Comp., pure carbon, 
 with often a little oxyd of iron mechanically mixed. 
 
 At Pitkin, in beds 2 feet thick; large masses at Trinidad; 
 small veins at Maysville, but very impure in each locality. 
 Graphite is largely employed under the name of Plumbago, 
 or Black Lead, for the manufacture of crucibles and other re- 
 fractory articles ; foundry facings, lubricating compounds, 
 electrical supplies, stove-polish, pencil leads and pigments. 
 It has an average spot value of 8 cents a pound. 
 
 SCHEEUTTE. Tungstate of Lime. Sittiman, Am. Jr. Sc., June, 1877. 
 
 Tetragonal ; primary form a right square prism ; occurs in attached and 
 imbedded four-sided pyramids, approaching nearly to the octahedron ; also 
 occurs reniforrn with columnar structure, and massive granular. Lustre 
 vitreous inclining to adamantine. Color white, yellowish-white to orange. 
 yellow, brownish, greenish. Streak white. Transparent to translucent, 
 H.- 4-5-5. G. 5'9. Comp., lime 19'4, tungstic acid 80'6. 
 
 Gold-bearing scheelite occurs in the Golden Queen mine, 
 Lake County. 
 
 Silicate of Vanadium. Genth, Am. Phi. Soc., Phila., 1877. 
 Micaceous in structure; scales minute, often arranged in stellate or fan - 
 shaped groups. Basal cleavage perfect. Color dark clover-brown to 
 greenish-brown. Analysis of Boulder County mineral by Genth : silica 
 56-74, alumina 19'62 ? vanadium 7'78, iron oxide 3'84, magnesia 2'63, po- 
 tassa 8'11, with traces of manganese, soda, lithium and water. 
 
 In the mines of Magnolia District, Boulder County, as a 
 thin earthy incrustation of a grayish to olive-green color on 
 calaverite; also inclosed in quartz, and giving it a green color. 
 
28 Minerals of Colorado. 
 
 HESSIXE. Telluric Silver. Silliman, Am. Jr. Sc., July, 1874. Genth, Am. 
 
 Phi. Soc., 1874. 
 
 Orthorhombic ; massive ; compact or fine-grained ; rarely coarse granular. 
 Lustre metallic. Color between lead-gray and steel-gray. Sectile and 
 malleable, laminating into thin scales under the pestle, leaving on the 
 agate surfaces metallic streaks of plumbago-like color. H. 2-3*5. G. 8*3 
 8'6. Analysis by Genth of mineral from the Red Cloud mine, Boulder 
 County : gold 0*22, silver 59;91, copper 017, lead 0.45, zinc trace, iron 1/35, 
 tellurium 37*86. An auriferous variety gave: gold 13*09, silver 50'36, tel- 
 lurium 34-91. * 
 
 Occurs abundantly in the Slide and Prussian mines, and 
 sparingly in other mines at Gold Hill and Sunshine, Boulder 
 County. 
 
 "WOlrFR. AMITK. Tungstate of Manganese. 
 
 Orthorhombic ; primary form a right rhombic prism ; occurs massive and 
 crystalized ; irregular lamellar ; coarse divergent columnar ; massive gran- 
 ular, the particles strongly coherent. Lustre submetallic. Color dark 
 grayish or brownish black. Streak dark reddish brown to black. Some- 
 times weak magnetic. H. 5-5*5. G. 7*1-7*55. Comp., tungstic acid 75*92, 
 Srotoxide of iron 19*35, protoxide of manganese 4*73. 
 ebrand mentions its occurrence in the Missouri mine, 
 Hall Valley, Park County, Occurs near Boulder. 
 
 UR.ANINITE. Pitchblende. Protoxyd of Uranium. Am. Jr. Sc., 1873. 
 Isometric ; usually massive and botryoidal ; also in grains. Structure 
 sometimes columnar, or curved lamellar. Lustre submetallic to greasy or 
 pitch-like, and dull. Color grayish, greenish, brownish, velvet-black. 
 Streak brownish, a little shining. Fracture conchoidal, uneven. H. 
 5*5. G. 6*4-8. Comp., protoxyd of uranium 32*1, sesquioxyd 67*9, but 
 analyses vary much through mixture with other substances. 
 
 A pocket of uraninite was encountered in the Wood lode, 
 Central City, in 1873, nearly all of which was shipped to Eng- 
 land by Kichard Pearce, esq., of the Boston and Colorado 
 Smelter, and sold for $1.50 per pound. Thin seams of the 
 mineral occur in Jefferson county. A mass of uraniuite 
 was encountered in the Jo Reynolds mines, Clear Creek 
 County, in 1885, but unfortunately, it was mixed with the 
 silver pre from the mine, and milled, the adulteration caus- 
 ing a serious loss to the miners. But two or three specimens 
 were saved, one of which is in the collection of the compiler, 
 also specimens from the Wood lode. 
 
 Uranium has the color and lustre of silver, but is harder, 
 and gives out sparks when struck with a hammer. It oxid- 
 izes gradually when exposed to the air, burns when heated 
 on platinum-foil, and is dissolved by nitric acid. Its specific 
 gravity is 18*7. Its compounds are used in considerable 
 quantities in chemical operations and in porcelain painting, 
 affording a yellow or black color, according to the process of 
 baking. 
 
Minerals of Colorado. 29 
 
 Telluride of Gold. Genth, Am. Phi. Soc.^ Phila., 1877. 
 Occurs massive and in small crystals. Color bronze-yellow. Streak yel- 
 lowish-gray. Brittle. Fracture uneven, inclining to subconchoidal. Anal- 
 ysis of Colorado mineral by Genth: tellurium 57'32, gold 38'75, silver 
 3*03, oxyd of vanadium 0'05, protoxyd of iron 0'03, alumina, magnesia,etc., 
 0-55, quartz 4'96. Theoretical formula, tellurium 57'93, gold 39'01, sil- 
 ver 3'C6. 
 
 In the Slide, Keystone J Mountain Lion and other mines, in 
 Boulder County. Small imperfect crystals imbedded in 
 quartz. 
 
 (new.} Genth, Am. Phi. Soc. Phil., 1877. 
 Tn delicate radiating tufts ; also in very minute prismatic crystals. Color 
 between straw and lemon-yellow, inclining to greenish-yellow. Contains 
 iron and tellurium. 
 
 Found as a coating on quartz associated with native tellu- 
 rium and tellurite, at ihe Keystone mine, Magnolia District, 
 Boulder County. 
 
 (new.) Variety of Native Tellurium. Genth, Am. Phi. Soc. 
 Phil., 1877. 
 
 Occurs in thin plates. Color dark gray. H. 3. G. 4'005. Analysis of 
 Colorado mineral by Genth : tellurium 55'54, quartz 35'91, alumina and 
 iron oxyd 6'14, manganese and iron oxide 0*19, calcium and iron oxide 
 0-26, gold 1-53, silver 0'25. 
 
 Occurs in the Mountain Lion mine, Boulder County, from 
 which it was named by Berdell. 
 
 (new). Telluride of Mercury. Genth, Am. Phi. Soc., 1877. 
 Occurs in radiating tufts of very minute acicular or capillary crystals. 
 Color white. Lustre silky. Contains mercury and tellurium. 
 
 Qccurs as a product of the decomposition of coloradoite in 
 the upper part of the Keystone, mine, Magnolia District, Boul- 
 der County. Named from Magnolia District. 
 
 Tellurious Acid. Genth, Am. Phi. Soc. Phil., 1877. 
 Occurs in prismatic crystals and in spherical masses, radiated in structure ; 
 also as an incrustation. Crystals cleavable in one direction. Color yellow 
 to white. 
 
 In the John Jay mine, Boulder County, as an incrustation 
 in cracks in native tellurium, and in minute prismatic crys- 
 tals. 
 
 CHRYSOCOLLA. Silicate of Copper. 
 
 Cry ptocrystal line ; often opal-like or enamel-like in texture; earthy; in- 
 crusti/ig or filling seams; sometimes botryoidal. Color various shades of 
 blue, passing into green. Streak, when pure, white. Translucent to 
 opaque. Fracture conchoidal. H. 2-4. G. 2'2. Comp., silica 34'2, oxyd 
 of copper 45'3, water 20'5. An analysis by Genth of what was supposed 
 to be chrysocolla, from Bergen Park, gave 33.85 alumina, and 5'40 of cop- 
 per oxide, which corresponds to allophane with probably some chrysocolla. 
 
 Found in copper lodes on Bear Creek; near Canon City ; 
 at the head of San Luis Valley; in the Champion lode, Idaho 
 Springs, and in small quantity in many other localities. 
 
30 Minerals of Colorado. 
 
 Cobalt Bloom. Ked Cobalt Ore. Cobalt Ochre. W. F. 
 Hillebrand, Am. Jr. Sc., May, 1884 ; Proc. Col. Sic. Soc., Vol. I. 
 Monoclinic; in acicular diverging crystals, modified at the edges, and 
 whose form is a right oblique-angled prism ; also found in globular and 
 reniform shapes, having a drusy surface and a columnar structure; some- 
 times stellate; also pulverulent and earthy, incrusting. Lustre vitreous 
 to earthy. Color crimson and peach-red, sometimes pearly or greenish- 
 gray ; red tints incline to blue perpendicular to cleavage face. Streak a 
 little paler than the color; the dry powder deep lavender-blue. Thin 
 laminae flexible in one direction. Sectile. H. rS-2'5, G. 2'94. Comp., 
 arsenic acid 38'43, oxyd of cobalt 37*55, water 24'02. 
 
 A product of the alteration of lollingite in the mines on 
 Teocalli Mountain, Brush Creek, Gunnison County. 
 
 AMPHIBOUE. Hornblende. 
 
 Monoclinic; crystals often long and bladed, sometimes stout; fibrous, col- 
 umnar, coarse or fine, fibers often like flax, when it is known by other 
 names. Color between black and white, through various shades of green, 
 inclining to blackish green. This species has numerous varieties, differing 
 much in external appearance and in composition. Silica, alumina, lime, 
 iron and magnesia enter into the composition. 
 
 Hornblende is an essential constituent of many of the rocks 
 of the mountainous region, such as hornblende gneiss, a 
 tough dark rock, which is quite abundant, seyenitc, trap., etc, 
 It is occasionally found massive and crystallized. 
 
 ASBESTOS. A variety of Amphibole. 
 
 Occurs in fine fibrous masses, of light color. 
 
 In the Star of the West and other lodes at the head of 
 of North Boulder Creek, Boulder County, associated with 
 galena. Near Maysville, Chaffee County, in mineral veins. 
 
 Asbestos was woven into cloth by the ancients, which, from 
 its incombustibility, was used to wrap the bodies of the dead 
 before placing them on the funeral pile, by which the ashes 
 were preserved for subsequent preservation in vases. Cloth- 
 ing was manufactured from it, which was cleansed by burn- 
 ing instead of washing. Its chief use now is for making tire- 
 proof roofing, boiler lining and lire proof safes. 
 
 TttEMOUTti. 
 
 The name given to the white or light greenish variety of Amphibole. It 
 occurs in long slender blades, or in columnar and radiated aggregations. 
 
 In white, radiated masses near Maysville, Chaffee County. 
 
 ACXIJJOWTE. A variety of Amphibole. 
 
 Fibrous, columnary or massive. Color bright green or grayish-green. 
 
 On Bear Creek, Jefferson County, in fibrous aggregations, 
 of a dark green color. In the mineral veins at the head of 
 North Boulder Creek, and in the Partridge lode, on Coal 
 Creek, Boulder County. Light green and bluish-green on 
 Mount Ouray. Specimens of the amphibole minerals in the 
 compiler's collection. 
 
Minerals of Colorado. 31 
 
 (new.} Telluride of Mercury. Genth, Am. Phi. Soc., 
 Phtta., 1877. 
 
 Massive ; granular, sometimes imperfectly columnar (due to admixed syl- 
 vanite?) Luster metallic. Color iron-black inclining to gray. Fracture 
 uneven to subconchoidal. Theoretical composition, tellurium 39'02, mer- 
 cury 60*98. Analyses of mineral from the Keystone and Smuggler mines 
 by Genth, varied a great deal on account of an admixture of gold and 
 quartz. That from the Keystone mine carried Irom 8 to 46 per cent of 
 gold and quartz, with small amounts of alumina, iron, vanadium and mag- 
 nesia. Mineral from the Smuggler mine contained quartz and gold, 3'05, 
 tellurium 34*49, mercury 48*74, gold 7*67, silver 7*18, iron 0*92, copper 0*16, 
 zinc 0-50. H. 3. G. 8'627. 
 
 Occurs sparingly in the Keystone, Smuggler and Mountain 
 Lion mines, Boulder county. 
 
 Soda Alum. 
 
 Occurs in white fibrous and pulverulent masses. Resembles fibrous gyp- 
 sum, but harder. H.3. G. 1'88. Reported analysis of Colorado mineral : 
 sulphuric acid 38*35, sulphate of alumina 14'66, sulphate of soda 4*35 
 water 42*64. 
 
 F. F. Chisolmn reports its occurrence in a lode one-and-a- 
 half miles shuth-east of Red Cliff. 
 
 Anhydrous Silicate of Zinc. 
 Rhombohedral ; occurs in regular six-sided prisms; also massive, fibrous 
 and in grains. Color whitish, yellowish, flesh-red, apple-green and dark- 
 brown. Streak same as color. Luster vitreo-resinous. Transparent to 
 opaque. Brittle. Fracture coochoidal. Double refracting. H. 5*5. G. 
 3-84-4*18. Comp., silica 27*1, oxyd of zinc 72*9. 
 
 Occurs sparingly at the head of the Rio La Plata as a pale 
 green crystalline mineral filling cavities in other zinc ores. 
 
 (new.) Sulphate of Manganese. M. W. lies, American Chemical 
 Journal, 1881. 
 
 Occurs in thick prisms which are frequently terminated by truncated pyr- 
 amids. Friable. Taste bitter, astringent. Color white. Soft. G. 2*16. 
 Analysis by lies: protoxyd of iron 4*18, oxyd of zinc 5*97, protoxyd of 
 manganese 22*31, sulphuric acid 36*07, water 31*60. 
 
 Occurs in veins from two to eight inches wide in the Mc- 
 Donnell lode, Middle Swan Creek, Hall Valley, Park county. 
 Named after Dr. M. W. lies. 
 
 CHAI.CAN'THITB. Blue Vitriol. Sulphate of Copper. 
 
 Triclinic; rarely found in distinct crystals; generally occurs stalactitic, 
 reniform, amorphous and pulverulent. Color Berlin-blue to sky-blue of 
 various shades ; sometimes greenish ; turns white on exposure. Translu- 
 cent. Luster vitreous. Taste metallic and nauseous. Comp., sulphuric 
 acid 32-1, oxyd of copper 31*8, water 36*1. 
 
 Occurs in a number @f mines in Hall Valley, Park county; 
 in the Whale tunnel, near Idaho Springs; in a deposit below 
 Black Hawk. It is formed by the decomposition of iron and 
 copper pyrites. When purified it is employed in cotton and 
 linen printing, and for various other purposes in the arts. It 
 is sometimes employed to prevent dry rot in wood. 
 
32 Minerals of Colorado. 
 
 SCHIR.MBR.IXE. (new.) Bismuth Silver. F. A. Genth, Proc. Am. Phi. 
 
 Soc., Phila., vol. 14, 1874. 
 
 Massive, without crystalline structure ; fine granular. Fracture uneven. 
 Brittle. Color lead-gray, inclining to iron-black. Luster metallic. Soft. 
 G. 6'737. Analysis by Genth : lead 12'76, silver 2475, bismuth 47'27, zinc 
 0'13, iron 0'07, sulphur 15'02. 
 
 First noticed in the Treasure Vault mine, Geneva district, 
 Clear Creek county, from whence the mineral came which 
 was analyzed by Mr. Genth. It occurs in all the older veins 
 in the district, finely disseminated through quartz. It has 
 never been noticed in the newer or subsequently-formed veins 
 which carry a large amount of galena, very little of which is 
 found in the bismuth-bearing veins. Dana's Mineralogy 
 credits the mineral to the lied Cloud mine, Boulder county, 
 where he says it "occurs with other tellurium minerals." 
 The location is erroneous, as the mineral has never been found 
 in that county. It was named after J. F. L. Scbirmer. The 
 schirmerite of Endlich was found to be a mixture of petzite 
 and some other minerals, and therefore not entitled to a name. 
 Specimens in compiler's cabinet. 
 
 Graphic Tellurium. Telluride of Gold and Silver. Silli- 
 man, Am. Jr. Sc., July, 1874, and Clarke, Oct., 1877 ; Genth, Am. Phi. 
 Soc., Phila., 1874. 
 
 Monoclinic ; occurs in indistinct and minute circular crystals, modified at 
 the edges and angles, and often grouped in rows, forming triangular figures 
 like letters; also massive, imperfectly columnar, granular. Cleavage in 
 two directions, nearly at right angles; one very perfect; Luster metallic. 
 Color steel-gray to tin-white and brass-yellow. Streak like color. H. l'5-2. 
 G. 5'732-8'28. Analysis by Genth of mineral from Red Cloud mine, Gold 
 Hill: gold 24-83, silver 13'05, tellurium 56'31, copper 0'23, zinc 0'45, iron 
 3'28, sulphur T82, selenium trace, quartz 0'32. Analysis of mineral from 
 Grand view mine, by Clarke : tellurium 52'96, gold 26'39, silver 10'55, 
 iron 4'45, sulphur 5*62. 
 
 Quite abundant in crystals and crystalline masses dissem- 
 inated .through quartz, in the the Red Cloud, Prussian, Cold 
 Spring and other veins at Gold Hill; in the American and 
 Grand View veins at Sunshine, Boulder county. Specimens 
 in compiler's cabinet. 
 
 Konig, Am. I hi. Soc., Phila., 1877. 
 Orthorhombic; usually in tabular prisms; often lengthened into strips 
 with parallel sides; easily cleavable. Luster submetalhc, pearlv. Color 
 bronze-yellow, gold-yellow, brownish. Powder like mosaic gold. Trans- 
 lucent and slightly elastic in thin leaves. H. 3. G. 3'324. Analysis by 
 Konig of Colorado mineral ; silica 34'68, titanic acid 13'58, zirconia 2'20, 
 sesquioxyd of iron 5'56, alumina 0'70, protoxyd of iron 26'10, protoxyd of 
 manganese 3'48, soda 2'54, potassa 5'01, water 3'54, magnesia 0'30, oxyd of 
 copper 0-42, tantalic acid (?) 0'80. 
 
 Beautiful specimens are found in veins on Cheyenne Moun- 
 tain, in quartz, associated with arfvedsonite and zircon. 
 Specimens in compiler's collection. 
 
Minerals of Colorado. 33 
 
 GARXBT. 
 
 Isometric; occurs in dodecahedrons, also in trapezohedrons, and both 
 forms are sometimes variously modified. Cleavage parallel to the faces of 
 the dodecahedron, rather distinct. Also found massive granular and 
 coarse lamellar. Color red, brown, yellow, white, apple-green, black; 
 some red and green colors often bright. Streak white. Lustre vitreous 
 resinous. Transparent subtranslucent. Fracture subconchoidal, uneven. 
 H. 6.5-7.5. G. 4'13. Composition varies, silica, alumina, iron, lime, etc. 
 There are three prominent varieties, based on the nature of the com- 
 position. (See Spessartite and Almandite.} 
 
 Red, brown and black garnets occur quite frequently in the 
 Archean. A reddish-brown garnet between Georgetown and 
 Green Lake,, and on Saxon Mountain. Quite abundant near 
 the head of Fall River, on Trail Creek, Bergen Park, Central 
 City, and other localities. A black variety in a vein near 
 Hoosier Pass. Small garnets, probably almandite, of beauti- 
 ful color, are found in quantities in the gold washings at Fair- 
 play and Breckenridge; impure alnwndite near Salida (p. 48). 
 Spessartite at Nathrop in rhyolite, and in the Grand Canon 
 of the Arkansas (p. j6). 
 
 UMONITB. Brown Iron Ore. Brown Ochre. 
 
 Usually in stalactitic and botryoidal or mammilary forms, having a fibrous 
 or subfibrous structure; also concretionary, massive, and occasionally 
 earthy. Lustre silky, often submetallic; sometimes dull and earthy. 
 Color of surface of fracture various shades of brown, commonly dark, and 
 none bright ; sometimes with a nearly black varnish-like exterior ; when 
 earthy, brownish-yellow, ochre-yellow. Streak yellowish-brown. H. 5 
 5'5. G. 3'6-4. Comp., sesquioxyd of iron 85'6, water 14*4. 
 
 A brown hematite of excellent quality is found in the Hot 
 Springs mine, Saguache County, which has been quite exten- 
 sively mined. At Villa Grove, in the same county. A bog 
 ore is found near Crested Butte. Analyses of ore from these 
 localities have been made at the State School of mines 
 
 Hot Villa Crested 
 
 Springs. Grove. Butte. 
 
 Silica 9-33 10'19 2'50 
 
 Water lO'ol 13'57 23'97 
 
 Alumina 3'43 3'60 0'28 
 
 Oxide of Manganese 0'35 
 
 Lime 0-83 0'45 0'22 
 
 Magnesia 0'06 0'22 0'12 
 
 Peroxide of Iron 75'23 70'39 72'47 
 
 Phosphoric acid 0'071 0'92 0'333 
 
 Sulphur 0-019 0'18 
 
 99-830 99-62 99'893 
 
 "This ore is a chemical curiosity," says Prof. Chauvenet, of 
 the State School of Mines, in speaking of the hematite' from 
 Crested Butte. "containing at once figures on certain constit- 
 uents which are phenomenal for highness and lowness respect- 
 ively. After burning this ore would be enriched to nearly 
 
34 Minerals of Colorado. 
 
 sixty-seven per cent of metallic iron by the loss of water and 
 organic matter." The ore is said to approximate to half a 
 mile square in extent, with an uncertain depth. 
 
 Limonite exists in numerous other localities between 
 South Boulder and Coal Creeks; on Bear Creek; in South 
 Park; at Trinided; beautiful specimens on Little Thompson, 
 at the foot of the mountains. 
 
 Carbonate of Soda. 
 Monoclinic. Vitreous to earthy. White, sometimes gray or yellow. 
 Taste alkaline. H. 1-1-5. G. T423. Comp., carbonic acid 26'7, soda 
 18'8, water 54'5. 
 
 About twelve miles south-west of Denver, between Turkey 
 and Bear Creeks, are four small lakes containing in solution 
 a large amount of soda. 
 
 MAGNETITE. Magnetic Iron Ore. Octahedral Iron Ore. 
 
 Isometric; octahedrons and rhombic dodecahedrons: cleavage octahedral. 
 Massive, and in particles of various sizes, sometimes impalpable. Lustre 
 metallic submetallic. Color iron-blacK. Streak black. Fracture sub- 
 conchoidal, shining. Brittle. Strongly magnetic, sometimes possessing 
 polarity. H' 5*5-6'5. G. 4'9-5'2. Comp., oxygen 27'6, iron 72'4. 
 
 The Calumet mine, ChafFee County, is the only iron mine 
 in the State producing magnetite, upon which the steel 
 works at Pueblo are largely dependent. The mine has been 
 opened to a depth of about 300 feet, and to a rmich greater 
 distance horizontally. Analysis by School of Mines, Golden: 
 
 Silica 7'04, alumina T90, peroxyd of iron 56'76, protoxyd of iron 26'88, bisul- 
 phide of iron 1'14, lime 1'59, magnesia T70, phosphoric acid 0*16, titanic acid 
 trace. 
 
 At Caribou a seven-foot vein of very pure ore. On Elk 
 Creek. 
 
 HEMATITE. Specular Iron. Red Ochre. 
 
 Rhombohedral ; in complex modifications of a rhombohedron ; crystals 
 occasionally thin tabular; also occurs granular, botryoidal, and stalactitic 
 shapes; lamellar, the laminae variously bent, and thick or thin. Lustre 
 metallic and occasionally splendent; sometimes earthy. Color dark steel- 
 gray or iron-black ; in very thin particles blood-red by transmtited light ; 
 when earthy, red. Streak cherry-red or reddish-brown. Sometimes at- 
 tractable by the magnet, and occasionally even magnetic-polar. H. 5'5- 
 6'5. G. 4'5-5'3. Comp., oxygen 30, iron 70. 
 
 An impure hematite occurs in the Hawkins bank, ChafFee 
 County. The following analysis of the ore was made at the 
 State School of mines: 
 
 Silica 22-33, water 3'10, alumina 3.06, lime 0'08, magnesia 0'06, peroxide of 
 iron 70'40, phosphoric acid 0'614, sulphur 0'056. 
 
 Occurs as an ochre near Florissant, with gothite, microcline, 
 quartz, fluorite, etc. A micaceous variety quite abundant on 
 Left Hand Breek, Ward District, Boulder County, and is 
 found in small quantities in numerous localities. 
 
Minerals of Colorado* 35 
 
 MUSCOVITE. Common Mica. Potash Mica. Oblique Mica. 
 
 Orthorhombic ; occurs in oblique rhombic prisms with basal cleavage ; 
 usually in thinly foliated masses ; folia often aggregated in stellate, or 
 globular forms. Lustre more or less pearly. Color white, gray, brown, 
 hair-brown, pale green, yiolet, yellow, dark olive-green, rarely rose-red ; 
 often different for transmitted and reflected light, and different also in 
 vertical and transverse directions. Streak uncolored. Transparent to 
 translucent. Thin lamina flexible, elastic, tough. Double refracting. 
 H. 2-2.5 G. 2.75-3.1. Comp., silica 46, alumina 37, potash 9, peroxyd of 
 iron 4, fluoric acid 1, water 2. 
 
 A constituent of much, of the Archean rocks, and occasion- 
 ally found in quite large masses. Several attempts have been 
 made to develop deposits in Jefferson and Clear Creek Coun- 
 ties, but without success. Near Canon City quite a large de- 
 posit which has been worked with limited success. 
 
 Magnesia-Mica. Hexagonal Mica. 
 Hexagonal ; prisms usually tabular, with perfect basal cleavage. Often in 
 disseminated scales, sometimes in massive aggregations or clsavable scales. 
 Lustre splendent, and more or less pearly on a cleavage surface, and some- 
 times submetallic when black ; lateral surface vitreous when smooth and 
 shining. Colors usually green to black, often deep black in thick crystals; 
 thin laminae green, blood-red, or brown by transmitted light ; rarely 
 white. Streak uncolored. Transparent to opaque. Tough and elastic. 
 H. 2.5-3. G. 2.7-3.1. Comp., varies, silica 39, alumina 15, peroxyd of 
 iron 8, magnesia 24, soda 1, potash 9, water 1, flluorine, chlorine, etc. 
 
 The mica of the Archean rocks is mainly biotite. It also 
 occurs in the dike rocks. 
 
 BISMUXIXE. Carbonate of Bismuth. 
 
 In implanted acicular crystallizations (pseudomorphs); also incrusting or 
 amorphous ; pulverulent. Lustre vitreous when pure ; sometimes dull. 
 Color white, mountain-green, and dirty siskin-green; occasionally straw- 
 yellow and yellowish-gray. Streak greenish-gray to colorless. Subtrans- 
 lucent opaque. H. 4-4.5. G. 6.86-6.909. 
 
 Near Cummens City, North Park. In the mountains west 
 of Fort Collins, where a number of veins have been prospect- 
 ed. In the L,as Animas mine, Gold Hill. In white quartz 
 on Guy Hill, Jefferson County, with bismuthinite. 
 
 Sulphuret of Manganese. 
 Isometric; in cubes and octahedrons. Cleavage, cubic perfect, crystals 
 sometimes cruciform, made of five combined octahedrons. Usually mass- 
 ive. Lustre submetallic. Color iron-black, tarnished brown on exposure. 
 Streak green. H. 3'5-4. G. 3'95-4'04. Comp., sulphur 36'7, manganese 
 63-3. 
 
 A ' 'pocket' ' of this mineral was encountered in sinking the 
 shaft on the Queen of the West mine, Summit County, about 
 300 feet from the surface. Occasionally crystals are met with. 
 The only immediate associate mineral is rhodochrosite, al- 
 though the mine carries galena, pyrite and argentite. The 
 alabandite carries about 30 ounces of silver to the ton. This 
 is the first published instance of its occurrence in America. 
 
36 Minerals of Colorado. 
 
 SPESSAR.XITK. Manganese- Alumina Garnet. W. Cross, U. S. Geo. 
 
 Sur., Am. Jr. Sc., June, 1866. 
 
 Isometric ; occurs in dodecahedrons, also in trapezohedrons, and both 
 forms are sometimes variously modified. Cleavage parallel to the faces of 
 the dodecahedron, rather distinct. Also found massive granular and 
 coarse lamellar. Color dark hyacinth-red, sometimes with a shade of 
 violet, to brownish-red. Streak white. Lustre vitreous resinous. Trans- 
 parent subtranslucent. Fracture subconchoidal, uneven. H. 6.5-7.5. 
 G. 4'13. Analysis of Nathrop mineral by L. G. Eakins: silica 35.66, 
 alumina 18.55, sesquioxyd of iron .32, protoxyd of iron 14.25, protoxyd of 
 manganese 29.48, lime 1.15, potassa .27, soda .21, water .44. 
 
 Occurs at Nathrop in lithophyses of rhyolite, associated 
 with topaz. In a similar rock in the Grand Canon of the Ar- 
 kansas. 
 
 EPIDOXE. 
 
 Monoclinic; in right rhomboidal prisms, more or less modified, often 
 with six or more sides ; also fibrous, divergent or parallel ; also granular, 
 particles of various sizes, sometimes fine granular and forming rock 
 masses. Lustre vitreous, inclining to pearly or resinous. Color pistachio- 
 green to brownish-green, greenish-black to black ; sometimes clear red and 
 yellow; also gray and grayish-white. Subtransparent opaque ; gener- 
 ally subtranslucent. Fracture uneven. Brittle. H. 6-7. G. 3.25-3.5. 
 Comp., silica 37.0, alumina 26.6, lime 20.0, protoxyd of manganese 0.6, 
 water 1.8. 
 Of frequent occurrence in the Archian, usually massive. 
 
 Very good crystals have been found on Floyd Hill and on 
 
 Bear Creek. 
 
 MALACHITE. Green Carbonate of Copper. 
 
 Monoclinic; rarely occurs crystallized ; usually massive or incrustating, 
 with surface tuberose, botryoidal or stalactitic, and structure divergent; 
 often delicately compact fibrous, and banded in color; frequently granular 
 or earthy. Lustre of crystals adamantine, inclining to vitreous ; fibrous 
 varieties more or less silky ; often dull and earthy. Color bright green. 
 Streak pale green. Translucent, subtranslucent, opaque. Fracture sub- 
 conchoidal, uneven. H. 3.5.74. G. 3.7 4.01. Comp., carbonic acid 
 19.9, protoxyd of copper 71.9, water 8.2. 
 
 Of general occurrence throughout the State near the sur- 
 face of mineral veins, but in small quantities, and usually as 
 incrustations. 
 
 CER.USSIXE. Carbonate of Lead. White Lead Ore. 
 
 Orthorhombic ; crystals usually thin, broad and brittle; sometimes stout; 
 rarely fibrous; often granular, massive and compact; sometimes stalactitic. 
 Lustre adamantine, inclining to vitreous or resinous ; sometimes pearly; 
 frequently submetallic if the colors are dark, or from a superficial change. 
 Color white, gray, grayish-black, yellowish, sometimes tinged blue or 
 green by some of the salts of copper. Streak uncolored. Transparent 
 subtranslucent. Fracture conchoidal. Very brittle. H. 3-3'5. G. 6.465- 
 6.480. Comp., carbonic acid 16.5, oxyd of lead 83.5. 
 
 Abundant at Leadville, and occasionally in fine crystalline 
 masses. Also abundant in numerous localities south of Lead- 
 ville. Occurs in small quantities at the surface of silver 
 veins in the Archian. 
 
Minerals of Colorado. 87 
 
 TIXAIVI'TE. Sphene. 
 
 Monoclinic; in very oblique rhombic prisms; crystals usually thin, with 
 sharp edges. Cleavage in one direction sometimes perfect. Occasionally 
 massive. Color grayish-brown, gray, brown or black ; sometimes yellow 
 or green ; streak uncolored. Lustre adamantine to resinous. Transparent 
 to opaque. Brittle. H. 5-5'5. G. 3'4-3'56. Comp., silica 30'5, titanic 
 acid 41-3, lime 28'2. 
 
 Occurs in crystals in the augitic rock on Italian Mountain, 
 Gunnison County. 
 
 CHRYSOWTE. Olivene. Peridot. 
 
 Orthorhombic; in right rectangular prisms, having perfect cleavage par- 
 allel with the smaller lateral plane ; usually in imbedded grains, of an ol- 
 ive-green color, looking like green bottle glass ; also yellowish-green. 
 Transparent to translucent. Looks much like glass in the fracture, except 
 in the direction of the cleavage. H. 6-7. G. 3'33-3'5. ' Comp., silica 38'5, 
 magnesia 48'4, protoxyd of iron 1T2, oxyd of manganese 0'3, alumina 0'2. 
 
 Occurs in the basalt of Bastion Peak. 
 
 PYROMOR.PHITE. Green Lead Ore. Phosphate of Lead. 
 
 Hexagonal ; occurs in six-sided prisms, usually modified on the edges, and 
 frequently striated horizontally ; often globular, reniform, and botryoidal, 
 with a subcolumnar structure; also fibrous and granular. Lustre resinous. 
 Color green, yellow and brown of different shades; sometimes wax-yellow 
 and fine orange-yellow ; also greenish-white or milk-white. Streak white, 
 sometimes yellowish. Subtransparent-stibtranslueent. Brittle. II. 3'5-4. 
 G. 6'5-7'l. Comp., phosphoric acid 15*7, oxyd of lead 74'1, chlorine 2'6, 
 lead 7-6 
 
 Sparingly in the mines at L/eadville, and in the Astor and 
 Freeland mines, Clear Creek County. 
 
 Hexagonal ; occurs in six and twelve sided prisms, with 
 plane or modified summits. Prismatic cleavage, distinct. Also massive, 
 compact, and thin columnar. Lustre vitreous, greasy; a little opalescent 
 in some varieties. Colorless, white or yellowish; also when massive, 
 dark green, greenish or bluish-gray, brownish and brick-red. Transpa- 
 rent-opaque. Fracture subconchoidal. H. 5*5-6. G. 2'5-2'65. Comp., 
 silica 44-2, glucina 337, soda 16'9, potash 5'2. 
 
 In the basalt of Bastion Peak and elsewhere in the Elkhead 
 Mountains. 
 
 AXIVABKRGITE. Nickel Ochre. Nickel Green. Arseniate of Nickel. 
 Monoclinic; in capillary crystals; also massive and disseminated. Color 
 fine apple-green, Streak greenish-white. Fracture uneven, or earthy. 
 Soft. Comp., arsenic acid 38'6, oxyd of nickel 37'2, water 24'2. 
 
 Occurs as an alteration product of niccolite in the Gem 
 mine, on Pine Creek, Fremont County. 
 
 CHAI,COCIT'E. Vitreous Copper Ore. Copper Glance. 
 
 Orthorhombic ; in six-sided prisms, variously modified ; also massive, 
 structure granular, or compact and impalpable. Lustre metallic. Color 
 and streak blackish lead-gray ; often tarnished blue or green. Fracture 
 conchoidal. Streak sometimes shining. H. 2'5-3. G. 5'5-5'8. Comp. 
 sulphur 20'2, copper 79'8. 
 
 Abundant in copper veins near Canon City; also in Bergen 
 Park and on Bear Creek, Jefferson County. 
 
38 Minerals of Colorado. 
 
 XAOYAGIXE. Black Tellurium. Foliated Tellurium. 
 
 Tetragonal ; occurs in small six-sided tables with a basal cleavage; also 
 massive-granular, but generally foliated. Lustre metallic, splendent. 
 Streak and color blackish lead-gray. Flexible in thin laminse. H. 1-1*5. 
 G. G-85-7'2. Comp., tellurium 15 to 32, sulphur 3 to 9, lead 50 to 60, gold 
 5 to 12. 
 
 Occasionally met with in the tellurium mines of Boulder 
 County. 
 
 GAUENI'FE. Galena. Sulphuret of Lead. 
 
 Isometric; occurs crystallized in the cube, octahedron, and in numerous 
 combinations of these, with planes of other figures; also in amorphous 
 masses with a lamellar structure; frequently granular ; occasionally fibrous. 
 Cleavage cubic. Lustre metallic. Color and streak pure lead-gray. Sur- 
 face of crystals occasionally tarnished. Sectile. Easily pulverized, and 
 easily frangible. H. 2 - 5-2'75. G. 4'25-7'7: Comp., sulphur 13*4, lead 86'6. 
 
 Of general occurrence throughout the mining regions, and 
 usually containing a profitable per cent of silver. Good crys- 
 tals only occasionally met with. Specially fine clusters have 
 been taken from the Dunderberg and Terrible mines, George- 
 town, and from the Running, Calhoun and Glennan mines, 
 in Gilpin County. 
 
 DECMENITE. 
 
 Occurs massive, botryoidal, nodular, stalactitic ; sometimes traces of a col- 
 umnar structure. Lustre of fresh fracture greasy. Color fine deep red to 
 yellowish-red and brownish-red ; also leather-yellow. Streak orange-yel- 
 low to pale yellow. H. 3-4. G. 5'6-5'81. Comp., vanadic acid 47, oxyd 
 of lead 53. 
 
 Occurs in the Evening Star mine, L/eadville, of dark red to 
 yellow color. 
 
 WIXHER.ITE. Carbonate of Baryta. 
 
 Orthorhombic ; in modified rhombic prisms and in six-sided prisms ter- 
 minated with pyramids; also in globular, tuberose and botryoidal forms ; 
 structure columnar, granular or amorphous. Lustre vitreous, inclining to 
 resinous, on surface of fracture. Color white, often yellowish or grayish. 
 Streak white. Subtransparent translucent. Fracture uneven. Brittle. 
 H. 3-3-75. G. 4'29-4'35. Comp., carbonic acid 22'3, baryta 777. 
 
 In white masses on Cotton Creek, San Luis Park. This 
 mineral is poisonous. 
 
 BAR.ITE. Heavy Spar. Sulphate of Baryta. 
 
 Orthorhombic; in modified rhombic and rectangular prisms; crystals 
 usually tabular; also columnar, fibrous, granular and compact. Lustre 
 vitreous, inclining to resinous, sometimes pearly. Streak white. Color 
 white, yellow, gray, blue, red, brown. Transparent, translucent, opaque. 
 Sometimes fetid when rubbed. H. 2'5-3'5. G. 4'3-4'8. Comp., sulphuric 
 acid 34, baryta 66. 
 
 Of frequent occurrence in the mines, both crystallized and 
 massive. Extensive beds on Vasquez River. Fine single 
 crystals with calcite on Apishapa Creek. Beautiful clusters 
 of crystals in the Seven-Thirty mine, Georgetown. Barite is 
 used as a paint, and in adulterating white lead. 
 
Minerals of Colorado. 39 
 
 CAL,CIXE. Calcareous Spar. Carbonate of Lime. 
 
 Rhombohedral ; occurs crystallized in upwards of 800 varieties of form. 
 The primary form is an obtuse rhombohedron, which may readily be ob- 
 tained by cleavage. Also fibrous, both coarse and fine ; sometimes lamel- 
 lar; often granular; also stalactitic. Lustre vitreous subvitreous earthy. 
 Color white or colorless, also various shades of red, green, gray, blue, yel- 
 low, violet ; brown and black when impure. Streak white or grayish. 
 Transparent opaque. Double refraction strong. G 2'508-2'776. H. 2'6- 
 3'5. Corup., carbonic acid 44, lime 56. 
 
 Large white masses on Bear Creek, five miles above Mor- 
 rison, in granite. On Box Elder Creek, Laramie County, in 
 aggregations of crystals, and in many other localities along 
 the base of the mountains. 
 
 ICELAKD SPAR. 
 
 Transparent variety of calcite. Double refracting in a high degree. 
 
 Near Canon City, on Beaver Creek; on the Greenhorn and 
 Apishapa; in the lava of the Table Mountains, Golden. 
 
 ARGENTINE. 
 
 A foliated, white pearly calcite. 
 
 On Chalk Mountains, in veins sometimes from two to three 
 feet thick. 
 
 MARBLE. Granular Limestone. 
 
 Calcite having a texture like loaf sugar when broken. The texture varies 
 from coarse to fine granular, and the latter passes by imperceptible shades 
 into compact limestone. The colors are various and usually clouded. 
 
 A large vein of black white and gray marble in South 
 Park. Brownish-gray marble near Canon City. Hard com- 
 pact limestone frequently makes a fine stone when polished. 
 A black variety veined with white occurs on Cotton Creek, 
 San Luis Park. Breccia marble near Boulder. Shell marble 
 near Colorado Springs. Encrinal marble at Sangre de 
 Christo Pass. 
 
 DESCLOIZIXB. 
 
 Orthorhornbic. Lustre bright. Color black to olive-brown ; smallest 
 crystals olive-green, with a chatoyant bronze lustre ; by transmitted light 
 along the edges light brown, inclining to red; on a surface of fracture, 
 colors zoned with straw-yellow, reddish-brown and black; nearly clear at 
 middle and darkest at extremities of crystal. H. 3*5. G. 5*839. Comp., 
 vanadic acid 29'3, oxyd of lead 70'7. 
 
 Sparingly in the Evening Star and other mines, Leadville. 
 
 Porcelain Clay. 
 
 Orthorhornbic; occurs in rhombic, rhomboidal, or hexagonal scales or 
 plates; sometimes in fan-shaped aggregations; usually constituting a clay- 
 like mass, either compact, friable or mealy. Lustre of plates pearly ; of 
 mass, pearly to dull earthy. Color white, grayish-white, yellowish, some- 
 times brownish, bluish or reddish. Scales flexible. Usually unctious and 
 plastic. H. 1-2-5. G. 2'4-2'63. Comp., silica 46, alumina 40, water 14. 
 
 Occurs as the result of the decomposition of the feldspars of 
 granitic rocks and porphyries throughout the state. Kaolin 
 is used in making porcelain and china ware. 
 
40 Minerals of Colorado. 
 
 VESUVIA1VITE. Idocrase. 
 
 Tetragonal ; crytals usually in modified square prisms ; also found massive. 
 Color brown to green, the latter frequently bright and clear ; occasionally 
 sulphur-yellow, and also pale blue. Lustre vitreous, often inclining to 
 resinous. Streak white. Subtransparent to nearly opaque. H. 6'5. G. 
 3'34. Comp., silica 38'4, alumina 23'7, protoxyd of iron 4'0, lime 29'7, 
 magnesia and protoxyd of manganese 5'2. 
 
 Occurs in beautiful yellowish-green crystals on Italian Mt. , 
 Gunnison County, which are said to be the finest found in the 
 United States. In brown crystals on Bear Creek. 
 
 AZURITE. Chessy Copper. Blue Carbonate of Copper. 
 
 Monoclinic; in modified oblique rhombic prisms, the crystals rather short 
 and stout; lateral cleavage perfect. Also massive, incrusting and earthy. 
 Lustre vitreous, almost adamantine. Color various shades of azure-blue, 
 passing into berlin-blue. Streak blue, lighter than the color. Transpa- 
 rent-subtranslucent. Fracture conchoidrl. Brittle. H. 3'5-52'5. G. 
 3'5-3'831. Comp., carbonic acid 25'6, oxyd of copper 69'2, water 5'2. 
 
 Occurs as on incrustation on the surface ores of many of 
 the mines throughout the state. 
 
 AR.SENOPYR.ITE. Mispickel. Arsenical Pyrites. 
 
 Orthorhombic ; crystallizes in right rhombic prisms, parallel to whose 
 planes it may be cleaved ; also occurs columnar, straight and divergent; 
 granular or* compact. Lustre metallic. Color silver-white, inclining to 
 steel-gray. Streak dark grayish-black. Fracture uneven. Brittle. H. 
 5-5-6. G. G'0-6-4. Comp., arsenic 46'0, sulphur 19'6, iron 44'4. Part of 
 the iron sometimes replaced by cobalt. 
 
 Occurs sparingly in some of the mines of Gilpin and Clear 
 Creek Counties. 
 
 CUPRITE. Eed Oxyd of Copper. 
 
 Isometric; in regular octahedrons and modified forms of the same. Cleav- 
 age octahedral. Also massive, granular ; sometimes earthy. Lustre ada- 
 mantine or submetallic to earthy. Color red, of various shades, particu- 
 larly cochineal-red ; occasionally crimson-red by transmitted light. Streak 
 brownish-red, shining. Subtransparent-subtranslucent. Fracture conch - 
 oidal, uneven. Brittle. H. 3'5-4. G. 5'85-6"15. Comp., oxygen 11"2, 
 copper 88*8. 
 
 In crystals, Sacramento Gulch, and in Sweet Home mine, 
 Buckskin. Malachite lode, Bear Creek. Massive at Poncha 
 Springs. 
 
 OPAL. 
 
 Massive, amorphous ; sometimes small reniform, stalictitic, or large tube- 
 rose. Lustre vitreous, frequently subvitreous ; often inclining to resinous, 
 and sometimes to pearly. Color white, yellow, red, brown, green, gray, 
 generally pale; sometimes a rich play of colors, or different colors by re- 
 fracted or reflected light. Transparent to nearly opaque. H. 5'5-6'5. G. 
 l'9-2:3. Comp., silica, same as quartz, with a little water. 
 
 A milk-white opal occurs in the decomposition product of 
 the lava on Buffalo Peaks, in the Mosquito Range. A yel- 
 lowish, slightly translucent opal is quite abundant six miles 
 south of the salt works, in South Park, associated with jasper 
 and chalcedony. 
 
Minerals of Colorado. 41 
 
 FIRE OPAL. 
 
 A variety of opal presenting hyacinth-red to honey-yellow and bluish col- 
 ors, with fire-like reflections, somewhat irised on turning. 
 
 A bluish transparent opal, with yellowish reflections, oc- 
 curs in a felsitic rick near Idaho Springs, which has been 
 used to considerable extent in jewelry. 
 
 MYAI.1XE. Muller's Glass. 
 
 An opal usually clear as glass and colorless, constituting globular concre- 
 tions, and also crusts with a globular, reniforrn, botryoidal, or stalactitic 
 surface. 
 
 Occurs near the head of Cache la Poudre Creek, and on the 
 La Garita, in pearly crusts, on lava. 
 
 WOOD OPAL. 
 
 Wood petrified by opal of various shades of color. 
 
 Abundant along the sources of Cherry,. Kiowa and Bijou 
 Creeks, at Happy Canon, and in Middle Park, much of which 
 is agate-like in structure, and of a diversity of colors. 
 
 BKRAL. 
 
 Hexagonal ; usually in long, stout six-sided prisms, without regular ter- 
 minations; occasionally coarse columnar. Lustre vitreous, sometimes res- 
 inous. Color bright green (when it is known as emerald], pale green, pass- 
 ing into light blue (aquamarine], yellow and white. Transparent-subtrans- 
 lucent. H. 7'5-8. G. 2'63-2 76. Comp., silica 66'8, alumina 19'1, glu- 
 cina 14'1. 
 
 Beryls of enormous size, but nearly opaque and of inferior 
 color, in white quartz, on Bear Creek. Small crystals of light 
 green color in the Floyd Hill region; also on the Platte River, 
 at the edge of South Park. Colorless and light green trans- 
 parent crystals on Mt. Antero, Chaffee County. 
 
 AQUAMARINE. 
 
 Beryls of a sea-green or pale bluish-green tint. 
 
 Beautiful transparent crystals, of bluish-green color, occur 
 on Mt. Antero, ChafFee County. Rarely on Bear Creek. 
 
 GOXMITE. Brown Iron-Stone 
 
 Orthorhombic; in prisms longitudinally striated, and often flattened into 
 scales or tables parallel to the shorter diagonal. Cleavage very perfect. 
 Also fibrous, foliated, in scales, massive, stalactitic. Lustre imperfect ad- 
 amantine. Color yellowish, reddish, and blackish brown. Often blood- 
 red by transmitted light. Streak browish-yellow, ochre-yellow. H. 5-5'5. 
 G. 4'6-4 4 Comp., sesquioxyd of iron 89'9, water lO'l. 
 
 Abundant in the Pike's Peak region, in cavities in granite, 
 associated with amazonstone, smoky quartz, fluor spar, etc. 
 
 BASTNASITE. Allen & Comstock, Am. Jr. Sc., May, 1880. 
 
 Hexagonal ; occurs in six-sided prisms. Color reddish-brown. Lustre 
 vitreous to resinous. H. 4-4'5. G. 5'18-5'20. Analysis of Colorado min- 
 eral by Allen & Comstock : oxide of cerium 40'88, oxide of lanthanum 
 and didymium 34'95, carbonic acid 20'09, fluorine (by difference) 4'08. 
 
 Occurs as an alteration product of tysonite west of Chey- 
 enne Mountain, El Paso County. 
 
42 Minerals of Colorado. 
 
 PTII^OUTE. (new.) W. Cross, Am. Jr. Sc., Aug., 1886. 
 
 Occurs in white tufts of short hair-like needles. Analysis by Eakins : sil- 
 ica 70-35, alumina 1T90, lime 3'87, potassa 2'83, soda 0'77, water 10'16. 
 
 Occurs as tufts of short hair-like needles in augite-andesite. 
 on the north slope of Green Mountain, Jefferson County. 
 
 ARAQOXITB. 
 
 Orthorhombic ; primary form a right rhombic prism ; occurs in hexagonal 
 prisms, very frequently in twin crystals, also in globular, reniform, den- 
 dritic, and coralloidal shapes; sometimes fibrous and in compact masses. 
 Color generally white, but sometimes tinged yellow, blue and green. Lus- 
 tre vitreous, inclining to resinous on fractured surfaces. Translucent to 
 transparent. Fracture subconchoidal. H. 3'5-4. G. 2'031. Cornp., car- 
 bonic acid 44, lime 56. 
 
 Coralloidal and in small masses in a number of lodes on 
 L,eavenworth Mountain, Georgetown. Near Golden. One 
 mile below Idaho Springs is a variety very similar to the cel- 
 ebrated gibralter rock, of Spain. In South Park, two 
 miles south-west of the Salt Works, in coarsely radiated and 
 columnar masses. On Willow Creek, San Luis Valley, a 
 vein about 30 feet wide, in basalt, portions of which exhibit 
 a botryoidal structure. Coralloidal at Loma. Six miles be- 
 low Del Norte, on the Rio Grande, a large deposit. 
 
 Chlorobromid of Silver. 
 Isometric; occurs in cubes and cubo-octahedrons ; also massive, sometimes 
 stalactitic. Lustre resinous and somewhat adamantine. Color grayish- 
 green and asparagus-green to pistachio or yellowish-green, and yellow, 
 often dark ; becoming darker externally on exposure. H. 1-1'5. G. 5*31- 
 5*43. Comp., varies, silver 61 to 71, bromine 7 to 33, chlorine 5 to 20. 
 
 Sparingly in the mines of L/eadville. 
 
 XYSONITE. (new.) Am. Jr. Sc., May, 1880, June, 1884. 
 
 Hexagonal; occurs in prisms with basal cleavage. Color pale wax-yellow. 
 Streak nearly white. Lustre vitreous to resinous. H. 4'5-5. G. 6'14. 
 Analysis by Allen & Com stock : cerium 40'16, lanthanum and didymium 
 30-29, fluorine 29'55. 
 
 Occurs near Pike's Peak, associated with bastnasite, both 
 minerals being frequently found in the same crystal, the cen- 
 tral portion of the crystal being composed of tysonite. Spec- 
 imens have been found weighing several pounds. Named 
 after S. T. Tyson, a metallurgist of Colorado. 
 
 PYR.IXE. Iron Pyrites. Bisulphuret of Iron. 
 
 Isometric; occurs in cubes, simple and modified; pentagonal dodecahe- 
 drons and octahedrons; crystals frequently forming aggregations; also 
 massive and in imitative shapes. Color bronze-yellow. Lustre metallic, 
 splendent. Brittle. H. 6-6'5. G.4'8-5'1. Comp., iron 467, sulphur 53'3. 
 
 Abundant in many of the mines, and usually valuable for 
 the gold and silver it contains. Beautiful cubical crystals in 
 the mines of Gilpin County. Dodecahedrons and cubo-octa- 
 hedrons in the Josephine mine, Geneva District, Clear Creek 
 County. 
 
Minerals of Colorado. 43 
 
 Rhombohedral ; usually in prisms terminating in a low pyramid ; cn-stals 
 usually hemihedral, being often unlike at the opposite extremities, or 
 hemimorphic, and the prisms often triangular. Sometimes massive com- 
 pact ; also columnar, coarse or fine, parallel or divergent. Lustre vitreous. 
 Color black, brownish-black, bluish-black, most common ; blue, green, red, 
 and sometimes of rich shades; rarely white or colorless ; some specimens 
 red internally and green externally ; and others red at one extremity, and 
 green, blue, or black at the other. Dichroic. Transparent opaque. Py- 
 roelectric. Brittle. H. 7-7'b. G. 2'94-3'3. Comp., black variety, silica 
 33, alumina 38, lime 1 protoxyd of iron 24, soda 3, boracic acid 1. 
 
 Fine black triangular prisms, with pyramidal terminations, 
 on Bear Creek, imbedded in white quartz. On Clear Creek, 
 two miles below black Hawk, hexagonal prisms in feldspar. 
 At Guy Hill. Five miles north of the Platte, on the road 
 from Colorado Springs to Fairplay, fine crystals with termin- 
 ations. 
 
 PETZITE. Tell u ride of Gold and Silver. 
 
 Orthorhombic. Massive; compact or fine-grained ; rarely coarse-granu- 
 lar. Lustre metallic. Color between steel-gray and iron-black, sometimes 
 with pavonine tarnish. Streak iron-black. Brittle. H. 2'5. G. 8'72- 
 8'83. Comp., tellurium 35, silver 47, gold 18. 
 
 In Boulder County, associated with other tellurium ores. 
 
 Orthorhombic; occurs in short tabular, six-sided prisms, with the bases 
 triangularly striated parallel to alternate edges. Cleavage basal, imper- 
 fect. Also massive and disseminated. Lustre metallic. Color iron-black; 
 in thin crystals cherry-red by transmitted light. Streak iron-black. Frac- 
 ture uneven. H. 2-3. G. 6'214. Analysis of polybasite from Terrible 
 mine, Georgetown, by Dr. Genth : sulphur 16'70, antimony 10'18, arsenic 
 0'78, silver 02'70, copper 9'57, iron 97. 
 
 In small quantity in many of the silver mines. Fine crys- 
 tals in the Little Emma and Colorado Central mines, George- 
 town. 
 
 TEXRAHEDRIXE. Gray Copper. Freibergite. Fahlerz. 
 
 Isometric; tetrahedral; occurs crystallized in modified tetrahedrons, and 
 also in compound crystals; also massive; granular, coarse or fine. Lustre 
 metallic. Color between light flint-gray and iron-black. Streak generally 
 same as the color: sometimes inclining to brown and cherry-red. Opaque; 
 sometimes subtranslucent in very thin splinters, transmitted color cherry- 
 red. Fracture subconchoidal uneven. Rather brittle. H. 3-4'5. G. 4'5, 
 5'11. Comp., varies; freiberyite, the argentiferous variety, sulphur 21 to 30, 
 antimony 17 to 28, copper 14 to 36, iron 1 to 7, zinc 1 to 6, silver 3 to 31. 
 
 Largely disseminated through nearly all sulphide silver 
 ores in the state. That from the mines about Georgetown 
 carries from 20 to 30 per cent of silver, while that from con- 
 tiguous districts, 3 or 4 miles from Georgetown, carries only 
 i or 2 per cent of silver. Good crystals, having pavonine 
 tints, in the Champion lode, Geneva District, Clear Creek 
 County. 
 
44 Minerals of Colorado. 
 
 Chalybite. Spathic Iron. Carbonate of Iron. 
 Bhombohedral ; occurs in obtuse rhombohedrons, whose faces are often 
 curved, in acute rhombohedrons, sometimes perfect, or having the terminal 
 angles replaced, and in lenticular crystals; also in botryoidal and globular 
 forms, subfi brous within, occasionally silky fibrous ; often cleavable mass- 
 ive, with cleavage planes undulating ; coarse or fine granular. Lustre vit- 
 reous, more or less pearly. Color ash-gray, yellowish-gray, greenish-gray, 
 also brown and brownish-red, rarely green, and sometimes white. Streak 
 white. Translucent subtranslucent. Fracture uneven. Brittle. H. 3'5- 
 4'5. G. 3'7-3'6. Comp., carbonic acid 37'9, protoxyd of iron 62'1. 
 
 Of frequent occurrence in the mines, both massive and crys- 
 tallized. 
 
 CYAXIfE. 
 
 Triclinic; usually in long-thin-bladed crystals aggregated together, or pen- 
 etrating the gangue; crystals sometimes short and stout. Lateral cleav- 
 age distinct. Sometimes fine fibrous. Lustre vitreous pearly. Color 
 blue, white, blue along the center of the blades with white margins; also 
 gray, green, black. Streak uncolored. Translucent transparent. H. 5-.7 
 G. 3'6-3'7. Comp., silica 37, alumina 63. 
 
 Occurs in the quartzite of Medicine Bow Peak. 
 
 TBTRAOYMIXE. Telluric Bismuth. 
 
 Hexagonal ; crystals often tabular. Cleavage basal, very perfect. Also 
 massive, foliated or granular. Lustre metallic, splendent. Color pale 
 steel-gray. Laminae flexible. Soils paper. H. l'5-2. G. 7'2-7'9. Comp , 
 tellurium 48, bismuth 52. 
 
 At Gold Hill, Boulder County, associated with other tel- 
 lurium ores. 
 
 Phosphate of Yttria. W. E. Hidden, Am.Jr.Sc., March,IS8a. 
 Tetragonal ; primary form a rectangular prism with a square base ; occurs 
 in square octahedrons, with perfect prismatic cleavage. Color yellowish- 
 brown, reddish-brown, hair-brown, flesh-red, grayish-white, pale yellow. 
 Streak pale brown, yellowish or reddish. Opaque. Fracture uneven and 
 splintery. H. 4-5. G. 4'45-4'56. Comp., phosphoric acid 37'86, yttria 
 62-14. " 
 
 Small chocolate-brown crystals west of Cheyenne Mountain, 
 El Paso County, from same locality as tysonite and bastnasite. 
 
 TORBERNI'TE. Copper-Uranite. 
 
 Tetragonal ; in square tables, often with replaced edges. Cleavage basal, 
 highly perfect, micaceous. Lustre pearly adamantine. Color emerald- 
 and grass-green, and sometimes leek-, apple- and siskin-green. Streak 
 somewhat paler than the color. Transparent subtranslucent. Sectile. 
 Laminae brittle and not flexible. H. 2-2'5. G. 3'4-3'6. Comp., phospho- 
 ric acid 15'7, oxyd of uranium 62'7, lime 6'1, water 15'5. 
 
 Sparingly in the Peabody lode, Georgetown. 
 
 BROMYRIXB. Bromic Silver. Bromid of Silver. 
 
 Isometric ; occurs in cubes, octahedrons and cu bo-octahedrons ; but gen- 
 erally in small concretions. Lustre splendent. Color when pure, bright 
 yellow to amber colored, slightly greenish ; often grass-green or olive- 
 green externally. Sectile. H. 2-3. G. 5'8-6. Comp., bromine 42'6, 
 silver 57*4. 
 Occasionally found in the mines at L/eadville. 
 
Minerals of Colorado. 45 
 
 COAL. 
 
 The distinguishing characters of mineral coal are as follows : Compact 
 massive, without crystalline structure or cleavage; sometimes breaking 
 with a degree of regularity, but from a jointed rather than a cleavage 
 structure. Sometimes laminated ; often faintly and delicately banded, suc- 
 cessive layers differing slightly in lustre. Lustre dull to brilliant, and 
 either earthy, resinous or submetallic. Color black, grayish-black, brown- 
 ish-black, and occasionally iridescent; sometimes dark brown. Opaque. 
 Fracture conchoidal uneven. Brittle; rarely somewhat sectile. Infus- 
 ible to subfusible; but often becoming a soft, pliant, or paste-like mass 
 when heated. On distillation most kinds afford more or less of oily and 
 tarry substances, which are mixtures of hydrocarbons and paraffin. Hard- 
 ness" 0-52-5. Gravity 1 1'80. 
 
 The varieties depend partly (i) on the amount of the vol- 
 atile ingredients afforded on destructive distillation; or (2) on 
 the nature of these volatile compounds, for ingredients of sim- 
 ilar composition may differ widely in volatility; (3) struct- 
 ure, lustre, and other physical characters. The following 
 varieties are found in Colorado: 
 
 BR.OWIV COAL. Lignite. 
 
 Sometimes pitch-Mack, but often rather dull and brownish-black. Fragile 
 compared with anthracite. Occasionally somewhat lamellar in structure. 
 
 The lignite coal area of Colorado extends from St. Vrains 
 on the north to the Raton Mountains on the south, about 220 
 miles in length, and varying from 20 to 35 miles in breadth 
 along the eastern base of the mountains. Large portions of 
 this field have been swept away by floods resulting from melt- 
 ing glaciers. The principal developments of this vast field 
 have been made in the vicinity of Boulder, Erie, L/oveland, 
 Golden, Colorado Springs, Coal Creek, Canon City, Walsen- 
 burg and Trinidad. Lignite also exists in North Park and 
 at various points on the divide between North and Middle 
 Parks. The following analyses have been made: 
 
 Water. Volatile Fixed Ash. Sul- 
 
 Matter. Carbon. phur. 
 
 Coal Hill, North Park 18'35 32'20 41'90 6'45 1.10 
 
 do do 8-82 41-56 4M7 6'00 2'45 
 
 Red Hill, do 15'20 3330 48'00 3'50 
 
 do do 10-50 37-30 50'30 1'90 
 
 No. 1, do 13-20 9-30 72-00 5'50 
 
 Erie Mine. Weld County 14'80 34'50 47'30 3'40 
 
 Marshal Mine, Boulder County .- 1200 26'00 59'20 2'80 
 
 Murphy Mine, Jefferson County 13'83 35'88 44'40 5'85 
 
 Golden, do do " 13'43 37'15 45'57 3'85 
 
 Franceville, El Paso County.... 12'90 . 29'10 46'00 12'00 
 
 Cutler banks, Uncompahgre County ... 7'26 43*42 41'72 7'60 
 
 JET. 
 
 Jet is a black variety of brown coal, compact in texture, and taking a good 
 polish, whence its use in jewelry. 
 
 Occurs in seams, from one-half to six inches in width, in 
 the shale about Canon Citv and Little Fountain Creek. 
 
46 Minerals of Colorado. 
 
 BIXUIJ11XOIJS COAI,. 
 
 Bituminous coals have the common characteristic of burning in the fire 
 with a yellow, smoky flame, and giving out on distillation hydrocarbon 
 oils or tar. They have usually a bright, pitchy, greasy lustre. The cak- 
 ing variety becomes pasty or semi-viscid in the fire. The softening takes 
 place at the temperature of incipient decomposition, and is attended with 
 the escape of bubbles of gas. On increasing the heat, the volatile products 
 which result from the ultimate decomposition of the softened mass are 
 driven off, and a coherent, grayish-black, cellular, or fritted mass (coke) is 
 left. A caking coal will lose its caking quality if kept heated for 2 or 3 
 hours at 300C., and sometimes on mere exposure for a time to the air. 
 Non-caking coal is like the preceding in all external characters, and often 
 in ultimate composition ; but burning freely without softening. The coke 
 is not a proper coke, being in powder, or of the form of the original coal. 
 
 The Trinidad group of mines, embracing those in the im- 
 mediate vicinity of Trinidad with those of ElMoro and Stark- 
 ville, and the mines at Crested Butte, are the most important 
 of this class in the State. Durango, Aspen and Rico are 
 other localities of its occurrence. 
 
 
 Water. Volatile Fixed 
 Matter. Carbon. 
 95 29'82 56'41 
 
 Ash. 
 
 12-82 
 4-32 
 6-30 
 4-47 
 3-09 
 
 
 ... '26 29'66 65'76 
 
 
 .... 3'23 40'93 49-54 
 
 
 .... 3'70 30'97 61'07 
 
 
 , -44 24-17 72-30 
 
 SEMI- BITUMINOUS. 
 
 Col. Coal and Iron Co., Park County 5'03 35'85 50'97 8'15 
 
 Oak Creek, do 672 3476 5270 5'82 
 
 Semi-bituminous coal is found principally in the mountain- 
 ous part of the state, The mines at Como on the South Park 
 railway are the most productive of this class. A good vein 
 has also been opened up on Mt. Carbon, 17 miles north-west 
 of Gunnison City. The coal from Walsenburg is by many 
 regarded as belonging to this class. 
 
 Color jet-black ; vandyke-brown when powdered. Has the appearance of 
 bituminous coal. Does not slack or break to pieces. In composition 
 much like albertite and torbanite. G. 1'323. Analysis by E. J. Mallett: 
 
 Water 6'02 
 
 Volatile matter 39'95 
 
 Fixed carbon and ash 54'03 lOO'OO 
 
 The locality of this new coal species is Middle Park. It is 
 a caking bituminous coal but yields an imperfect coke. In 
 comparison with English cannel coal it gives thirty per cent 
 more gas of a high illuminating power. It is named after 
 Mr. W. N. Byers. 
 
 NATIVE COKE. 
 
 More compact than artificial coke, and sometimes affording considerable 
 bitumen. 
 
 The origin of native coke is attributed to the action of a 
 
Minerals of Colorado. 4j 
 
 trap eruption on bituminous coal. It has been found near 
 Crested Butte where a dike of lava has intruded the coal 
 strata. It has also been found at Trinidad. 
 
 ANTHRACITE;. 
 
 Lustre bright, often submetallic, iron-black, and frequently iridescent. 
 Fracture conchoidal. Volatile matter afttr drying 3 to 6 per cent. Burns 
 with a feeble flame of a pale color. H. 2-2'5. 
 
 Anthracite coal appears to be confined mainly to the coal 
 basins in the Elk Mountains, and extends over a large scope 
 of country. These mountains are composed of lofty peaks of 
 eruptive rock, and are separated from the plains by three par- 
 allel ranges, the Colorado or Front Range, the Park Range 
 and the Saguache Range, separated from one another by 
 trough-like valleys and parks. The coal fields are in the 
 same geological horizon as that of the plains, and the coal 
 is much the same, metamorphosed or changed by heat into 
 anthracite, and on the outer edges of the basins graduates 
 into lignite. On Anthracite Mesa, near Crested Butte, the 
 veins are from two to ten feet thick. Analyses show 
 
 Water. Volatile Fixed Ash. 
 
 Matter. Carbon. 
 
 Crested Butte, Gunnison County ....................... T20 5'16 90*24 3'40 
 
 Anthracite Creek, do ....................... 2'00 2'50 9190 3'60 
 
 Anthracite Mesa, do ....................... 5'17 90'85 4'18 
 
 Rock Creek, do ....................... 7'40 88'90 3'68 
 
 SEMI-ANTHRACITE. 
 
 W. & D. Trust Co., Crested Butte ..................... 4'00 14'00 74'00 8'00 
 
 Uncompahgre Canon ..................................... 1/86 10'70 77'32 1012 
 
 PETRO1LBUM. Naptha. Mineral Oil. Kerosene. 
 
 A fluid bitumen of dark color, which oozes from certain rocks and becomes 
 solid on exposure, forming asphaltum. Com., carbon 82'2, hydrogen 14'8. 
 
 Oozes from sandstone near Morrison. Six oil wells are in 
 operation in the neighborhood of Canon City and Florence, in 
 Fremont county. The Oil Creek well, which was sunk in 
 1862, turned out about 3,000 gallons of oil. 
 
 ASPHAI/TUM. Bitumen. Mineral Pitch. 
 
 Amorphous. Lustre like that of black pitch. Color brownish-black and 
 black. Odor bituminous. Melts ordinarily at 90 to 100 C., and burns 
 with a bright flame. Soluble mostly or wholly in oil of turpentine, and 
 partly or wholly in ether; commonly partly in alcohol. The more solid 
 kinds gradate into the pittasphalts or mineral tar, and through these is a 
 gradation to petroleum. Comp., carbon 75'0, hydrogen 9'5, oxygen 15'5. 
 
 Fluid bitumen oozes from sandstone near Morrison and 
 forms an earthy asphaltum. In the White River region and 
 near Canon Cit. 
 
 RKSIN. 
 
 Mineral resin occurs Jin the coal in scales, and small masses 
 have been found in the soil on the Table Mountains, but the 
 
48 Minerals of Colorado. 
 
 species have not been determined. Prof. Wm. P. Headden 
 mentions the occurrence of a substance in coal from the 
 Mitchell mine, Brie, which he believes to be napthaline. It 
 occurs in microscopic, tabular crystals, which are thin, color- 
 less and transparent. 
 
 TURGIXB. 
 
 Compact fibrous and divergent, to massive; often botryoidal and stalactitic 
 like limonite. Also earthy, as red ochre. Lustre submetallic and some- 
 what satin-like in the direction of the fibrous structure; also dull earthy. 
 Color reddish-black, to dark red ; bright-red when earthy ; botryoidal sur- 
 face often lustrous, like much limonite. Opaque. H" 5-6. G. S'56-3'74. 
 Comp., Sesquioxyd of iron 94*7. water 5'3. 
 
 Occurs in small botryoidal masses, of reddish-black color, 
 and highly polished surfaces, at Florissant, associated with 
 gothite, amazonstone, smoky quartz, etc. 
 
 Iron-Alumina Garnet. Precious or Oriental Garnet. 
 Isometric; occurs in dodecahedrons and trapezohedrons, both forms some- 
 times variously modified ; rarely in octahedrons. Cleavage parallel to 
 the faces of the dodecahedron. Also found massive. Color fine deep-red 
 and transparent, and then ealled precious garnet; also brownish-red, and 
 translucent or subtranslucent. Streak white. Lustre vitreous resinous. 
 Fracture subconchoidal, uneven. H. 6'5-7"5. G. 4'13. Comp., silica 36'1, 
 alumina 20*6, protoxyd of iron 43 '3. 
 
 L/arge and perfect dodecahedrons, some of them measuring 
 six inches in diameter, occur in chlorite near Salida, Chaffee 
 County. Several thousand specimens have been taken out 
 of a single "pocket." They are usually coated with chlorite, 
 and the surfaces of the garnets are decomposed, the decempo- 
 sition product forming aphrosiderite. The color of the garnet 
 is brownish-red. Analysis by S. L. Penfield and F. L/. Sperry 
 gave the following: 
 
 Silica ...................................... 37-61 
 
 Alumina ................................. 2270 
 
 Protoxyd of Iron ...................... 33'83 
 
 Protoxyd of Manganese .............. 1*12 
 
 Magnesia ................................. 3'61 
 
 Lime ...................................... 1'44 
 
 100-31 
 
 Beautiful dark red garnets, which can probably be classed 
 as precious garnets, are abundant in the placers at Fairplay 
 and Breckenridge. The are usually quite small and of no 
 value as gems. 
 
 APHROSIDBRITE. 
 
 A soft ferruginous chlorite, of a dark olive-green color, scaly massive in 
 structure ; the scales minute, transparent, and hexagonal. 
 
 Occurs as an alteration product on the garnets found at Sa- 
 lida, forming a coating- of light green color. Analysis by 
 Penfield and Sperry gave: 
 
Minerals of Colorado. 49 
 
 Silica ...................................... 28-20 
 
 Alumina ................................. 22'31 
 
 Protoxydof Iron ....................... 19'11 
 
 Protoxyd of Manganese .............. 17*68 
 
 Lime ..................................... '48 
 
 Soda ...................................... 72 
 
 Potassa ............... .. ................... 1'03 
 
 Water .................................... 10'90 
 
 FAYAI^IXB. Iron Chrysolite. Anhydrous Silicate of Iron. 
 
 Massive, crystalline. Cleavage in two directions at right angles to one 
 another. Lustre metalloid, somewhat resinous in the fracture. Color 
 black ; sometimes iridescent. Opaque. Fracture imperfectly conchoidal. 
 Attractable by the magnet. H. 6'5. G. 4-414. Com p., silica 29'5, pro- 
 toxyd of iron 70'5. 
 
 Occurs in quite large masses in Cheyenne Canon, El Paso 
 County. 
 
 FIRROWTK. 
 
 Monoclinic ; crystals commonly long and slender. Cleavage brilliant and 
 perfect. Also occurs fibrous or columnar massive, sometimes radiating. 
 Lustre vitreous, subadamantine. Color hair-brown, grayish-brown, gray- 
 ish-white, grayish-green, pale olive-green. Streak uncolored. H. 6-7. 
 G. 3-2. Comp., silica 36'8, alumina 63'2. 
 
 Occurs in small fibrous masses, of grayish-green color, on 
 Sherman Mountain, near Georgetown. 
 
 SAXIDIK. Glassy Feldspar. Whitman Cross, Am. Jr. Sc., Feb., 1884. 
 
 A variety of orthoclase (p.12) occurring in transparent glassy crystals, 
 mostly tabulur, in eruptive rock. 
 
 Mr. Cross describes the occurrence of sanidin in the nevad- 
 ite of Chalk Mountain, and rhyolite of Ragged Mountain, 
 which possesses a satin lustre. Smoky quartz and topaz are 
 associates of the sanidin in the nevadite. Also occurs in rhy- 
 olite at Nathrop, with the same associate minerals. 
 
 Pearl Spar. Brown Spar. Magnesian Limestone. 
 Rhombohedral ; crystals often having curved faces. Cleavage perfect 
 parallel to the primary faces. Often granular and massive, constituting 
 extensive beds. Color white or tinged with yellow, red, green, brown and 
 sometimes black. Lustre vitreous or a little pearly. Nearly transparent 
 to translucent. Brittle. H. 3'5-4. G. 2'8-2'9. Comp., carbonate of lime 
 54'35, carbonate of magnesia 45'65. 
 
 Occurs in extensive beds in various portions of the State, 
 and in small quantities in the mines, frequently crystallized. 
 
Acanthite, 13 
 
 Bismuthinite, 9 
 
 Chrysolite, 37 
 
 Actinolite, 30 
 
 Bismutite, 35 
 
 Citrine, 24 
 
 Agate, 18 
 
 Bitumen, 47 
 
 Cobalt, Arsenate, 30 
 
 Agatized Wood, 18 
 
 Bituminous Coal, 46 
 
 Arsenide, 8 
 
 Alabaster, 26 
 
 .B/ac& Tellurium, 38 
 
 Iftoom, 30 
 
 Alabandite, 35 
 
 Black Lead, 27 
 
 Columbite, 19 
 
 Alaskaite, 8. 
 
 Blende, 25 
 
 Coloradoite, 31 
 
 Allanite, 21 
 
 Bloodstone, 17 
 
 Common Mica, 35 
 
 Alamandite, 48 
 
 .B/we Carbonate Copper, 40 
 
 Common Salt. 25 
 
 yl/oite, 12 
 
 ke yftno/, 31 
 
 Copper, Carbonate, 36, 40 
 
 Allophane, 21 
 
 tfo/e, 17 
 
 O/ance, 37 
 
 ^4/toite, 21 
 
 Bornite, 14 
 
 Native, 6 
 
 vlfotra, Native, 23 
 
 Bromyrite, 44 
 
 Oxide, 40 
 
 Amazonstone, 12 
 
 Brochantite, 10 
 
 Pyrites, 9 
 
 Amethyst, 23 
 
 Bromid of Silver, 44 
 
 SiJieate, 29 
 
 Amphibole, 30 
 
 Bromic Silver, 44 
 
 Sulphate, 10, 31 
 
 Analcite, 15 
 
 Brown Coal, 45 
 
 Sulphide, 37 
 
 Anglesite, 7 
 
 Brown Iron Ore, 41 
 
 Uranite, 44 
 
 Annabergite, 37 
 
 Brown Ochre, 33 
 
 CosaMe, 13 
 
 Anthracite, 47 
 
 Brown Spar, 49 
 
 Covellite, 19 
 
 Antimony Glance, 23 
 
 Byerite, 46 
 
 Cryolite, 11 
 
 Aphrosiderite, 48 
 
 
 Cuprite, 40 
 
 Apophyllite, 15 
 Aquamarine, 41 
 
 Cairngorm, 24 
 
 Cyanite, 44 
 
 Aragonite, 42 
 Arfvedsonite, 22 
 Argentite, 13 
 Argentine, 39 
 Arsenide of Cobalt, 8 
 
 Calaverite, 29 
 Ca/ctte, 39 
 Calcareous Spar, 39 
 Carnelian, 17 
 Carbonate Bismuth, 35 
 
 7)ar^ fled StVwer Ore, 19 
 Dechenite, 38 
 Desdoizite, 39 
 Dolomite, 49 
 
 J.T01l>) u 
 
 Arsenopyrite, 40 
 Arsenical Pyrites, 40 
 Ar senate of Nickel, 37 
 Arsenical Nickel, 7 
 Asbestus, 30 
 Asphaltum, 47 
 Astrophyllite, 32 
 Autunite, 13 
 
 Soda, 34 
 7ron, 44 
 Baryta, 38 
 Copper, 40 
 Lead, 36 
 
 Manganese, 10 
 Gassiterite, 21 
 G&sfo'te, 25 
 
 Egyptian Jasper, 24 
 Elpasolite, 20 
 Embolite, 42 
 Enargite, 13 
 Epid'ote, 36 
 Erythrite, 30 
 Erubescite, 14 
 J5<ye ,4 pate, 18 
 
 ^iiZttTitC) 40 
 
 Cerargyrite, 24 
 
 FaMerz, 43 
 
 
 Cerussite, 36 
 
 Fa/se Topaz, 24 
 
 Banded Agate, IS 
 
 Chabazite, 14 
 
 Fayalite, 49 
 
 Barite, 38 
 
 Chalcanthite, 31 
 
 Feldspar, 12 
 
 Bastnasite, 41 
 
 Chalcedony, 14 
 
 FtrroteUurite, 29 
 
 Beegerite, 8 
 
 Chalcocite, 37 
 
 Fibrolite, 49 
 
 Beryl, 41 
 
 Chalcopyrite, 9 
 
 Fibrous Gypsum., 26 
 
 Biotite, 35 
 Bismuth, Carbonate, 35 
 Glance, 9 
 
 Chalybite, 44 
 CAes.st/ Copper, 40 
 CMort'd o/ /Si/twr, 24 
 
 Fibrous Heavy Spar, 25 
 I' ire OpaZ, 41 
 Fluorite, Fluor Spar, 10 
 
 Native, 6 
 
 Sodium, 25 
 
 Foliated Tellurium, 38 
 
 S/foer, 32 
 
 Chrysocolla, 29 
 
 Fortification Agate, 18 
 
 Sulphide, 9 
 
 Vhn/soprase 18 
 
 Freibergite, 43 
 

 INDEX. 
 
 
 Gadolinite, 26 
 
 Levynite, 16 
 
 Nickel Green, 37 
 
 Gahnite, 22 
 
 Lt<7/&< JFfat&y Silver Ore, 1 9 
 
 OcAre, 37 
 
 Galenite, Galena, 38 
 
 Lignite, 45 
 
 Telluride, 7 
 
 Garnet, 33 
 
 Lime Uranite, 13 
 
 Niccolite, 7 
 
 Gearksutite, 11 
 
 Limonite, 33 
 
 
 Glassy Feldspar, 49 
 GWd, 5 
 
 Lionite, 29 
 Lollingite, 9 
 
 Oblique Mica, 35 
 Octahedral Iron Ore, 34 
 
 Gothite, 41 
 
 
 Oiivene, 37 
 
 Graphite, 27 
 Graphic Tellurium, 32 
 Crrai/ Copper, 43 
 Green Carbonate Copper, 36 
 #reen Lead Ore, 37 
 
 Magnetite, 34 
 Malachite, 36 
 Manganese, Carbonate, 10 
 6?ame, 36 
 Sulphate, 31 
 
 Ora/z, 18 
 OpaZ, 40 
 Oriental Garnet, 48 
 Orthodase, 12 
 
 Guitermanite, 9 
 Gypsum, 26 
 
 ITaftte, 25 
 
 Heavy Spar, 38 
 Heliotrope, 17 
 Hematite, 34 
 Hessite, 28 
 
 Sulphide, 35 
 Magnesian Limestone, 49 
 Magnetic Iron Ore, 34 
 Magnesia Mica, 35 
 Magnesia Alum, 23 
 Magnolite, 29 
 JfairWe, 39 
 Melonite, 7 
 
 Pachnolite, 11 
 Pear/ Spar, 49 
 Peridot, 37 
 Petroleum. 47 
 Peteite, 43 
 Phenacite, 7 
 Phosphate of Lead, 37 
 
 TT-, , , * 
 
 Hexagonal Mica, 35 
 Hornblende, 30 
 LTorn Silver, 24 
 Hubnerite, 17 
 Hyalite, 41 
 
 Mendozite, 31 
 Mesolite, 16 
 Mercury, Native, 5 
 Telluric, 44 
 Telluride, 29, 31 
 Micaceous Iron 34 
 
 Yttna, 44 
 Pickeringite, 20 
 Pitchblende, 28 
 Pitchstone, 12 
 Plumbago, 27 
 Polybasite, 43 
 
 Iceland Spar, 39 
 Idocrase, 40 
 Ilesite 31 
 
 Microclin, 12 
 Mineral Coal, 45 
 Oi/. 47 
 
 Porcelain Clay, 39 
 PofasA ,4/?/m,'28 
 Potas/t Feldspar, 12 
 
 /ran, Arsenide, 9 
 Arsenical, 40 
 Carbonate, 44 
 Chrosolite, 49 
 Columbate, 19 
 <?ame, 48 
 Oxide, 33, 34, 41, 48 
 Pyrites, 42 
 Silicate, 49 
 Sulphate, 7 
 Sulphide, 42 
 
 PiteA, 47 
 Resin. 47 
 Mispickel, 40 
 J/ocAa Stone, 18 
 Molybdenite, 25 
 .Moss ^4<7a<e, 18 
 Morion, 24 
 Mutter's Glass, 41 
 Muriate of Soda, 25 
 Muscovite, 35 
 
 Potash Mica, 35 
 Prase, 18 
 Precious Garnet, 48 
 Prosopite, 11 
 Proustite, 19 
 Protoxyd of Uranium, 28 
 Ptilolite, 42 
 Purple Copper Ore, 14 
 Pyrargyrite, 19 
 Pyromorphite, 37 
 Pyrite, 42 
 
 
 Nagyagite, 38 
 
 
 Jarosite, 7 
 
 Naptha, 47 
 
 Qwarte, 23 
 
 Jasper, 24 
 
 Natrolitc. 16 
 
 Quicksilver, 5 
 
 Jet, 45 
 
 Natron, 34 
 
 
 
 Native Alum, 23 
 
 Radiated Zeolite, 14 
 
 Kalinite, 23 
 
 Bismuth, 6 
 
 Rcdstonite, 19 
 
 Kaolinite, 39 
 
 (Me, 46 
 
 .Red Oo6a/ Ore, 30 
 
 Kerosene, 47 
 
 Copper, 6 
 
 ^ed OcAre, 34 
 
 Kobellite, 27 
 
 6rO/d, 5 
 
 .Red Oxide o/ Copper, 40 
 
 
 Mercury, 5 
 
 ^ed ASi/uer Ore, 19 
 
 Laumonite, 15 
 
 Silver, 5 
 
 Rhodochrosite, 10 
 
 Lead, Carbonate, 36 
 
 Sulphur, 6 
 
 Ribbon Jasper, 24 
 
 Phosphate, 36 
 
 Tellurium, <> 
 
 JRoefc Crystal, 23 
 
 Sulphate, 7 
 
 iVeed/e Zeofo'fe, 16 
 
 Rock Salt, 25 
 
 Sulphide, 38 
 Telluride, 21, 38 
 
 Nephelite, 37 
 Nickel, Arsenate, 37 
 
 Roscoelite, 27 
 ^ose Quartz, 24 
 
 Vanad,ate, 38, 39 
 
 Arsenical, 7 
 
 Kw6t/ Sifoer Ore, 19 
 
INDEX. 
 
 Sanidin, 49 
 
 Sulphate of Lime, 26 
 
 Tourmaline, 43 
 
 Salt, 25 
 
 Manganese, 31 
 
 Tremolite. 30 
 
 Sardonyx, 18 
 
 Strontia, 25 
 
 Tysonite, 42 
 
 Satin Spar, 26 
 
 Sulphide of Antimony, 23 
 
 Tungstate of Lime, 27 
 
 Schedite, 27 
 
 Bismuth, 7 
 
 Magnesia, 17 
 
 Schirmerite, 32 
 
 Copper, 19 
 
 Manganese, 28 
 
 Scolecite, 16 
 
 /row, 42 
 
 Z\*r$r;te, 48 
 
 e/enite, 26 
 
 ead, 38 
 
 
 Siderite, 44 
 Siftcafe o/ Iron, 49 
 
 Manganese, 35 
 Molybdena, 25 
 
 Uraninite, 28 
 
 Silver, Chloride, 24 
 Chloro- Bromide, 42 
 
 tfiteer, 13, 
 Zirac, 25 
 
 Vesuvianite, 40 
 
 Bismuth, 32 
 
 Sulphur, Native, 6 
 
 FV^-eows Copper Ore, 37 
 
 M?, 14 
 
 Sylvanite, 32 
 
 Volcanic, Glass, 12 
 
 Bromic, 44 
 
 
 
 frlnnrc 1 '? 
 
 
 
 \jriUjliLti, -LO 
 
 Native, 5 
 
 Telluric Bismuth, 44 
 
 tfito'te iea^ Ore, 36 
 
 Sulphide, 13 
 Telluride, 29, 32 
 Smaltite, 8 
 Smoky Quartz, 24 
 
 Teilurious Acid, 29 
 Telluride of Gold, 29 
 . ead,21 
 Mercury, 29,31 
 
 Willemite, 31 
 Witherite, 38 
 Wolframite, 28 
 Food OpaJ 41 
 
 /Soda J.^m, 31 
 
 Mdfce/, 7 
 
 
 Specular Iron, 34 
 
 Tellurite. 29 
 
 Xenotime, 44 
 
 Spessartite, 36 
 
 Tellurium, Native, 6, 29 
 
 
 Spathic Iron, 44 
 Sphalerite, 25 
 Sphene, 37 
 Stibnile, 23 
 ,ite, 14 
 
 Tennantite, 8 
 Tetradymite, 44 
 Tetrahedrite 43 
 Thomsenolite, 1 1 
 Thomsonite, 15 
 
 Zinc Blende, 25 
 Silicate, 27, 31 
 Spme/, 22 
 Sulphide, 25 
 
 Sulphate of Baryta, 38 
 Copper, 31 
 /row, 7 
 
 Tm ^tone, 21 
 Titanite, 37 
 Topaz, 22 
 
 Zinkenite, 8 
 Zircon, 2C 
 Zunyite, 12 ' 
 
 Lmd, 7 
 
 Torbernite, 44 
 
 
E3VSTATITE. Bronzite. Protobastite. W. Cross, Bulletin No. 1, U. S. 
 
 Geological Survey. 
 
 Orthorhombic; primary form an oblique four-sided prism with a very dis- 
 tinct cleavage parallel to the lateral planes; sometimes a fibrous appear- 
 ance on the cleavage surface; also occurs massive and lamellar. Lustre a 
 little pearly on the cleavage-surfaces to vitreous; often metalloidal in the 
 "bronzite variety. Color grayish-white, yellowish-white, greenish-whits, to 
 olive-green and brown. Streak uncolored, grayish. Double refraction 
 positive. H. 5'5. G. 31 3'3. Composition : 
 
 Silica .................................... 60 
 
 Magnesia .............................. 40 
 
 Sometimes iron, alumina, etc. - 
 
 100 
 
 Whitman Cross gives the occurrence of an enstatite-bearing 
 diabase in a narrow dike of dark rock at Morrison. 
 
 Iron Potash Mica. 
 Hexagonal ; occurs in small six-sided tables, or an aggregation of minute 
 opaque scales, with perfect basal cleavage. Lustre adamantine, inclining 
 to vitreous, pearly. Color black with occasionally a leek-green reflection. 
 Streak grayish-green. Opaque or translucent in very thin laminae. Some- 
 what brittle, or but little elastic. H. 3. G. 3. Composition : 
 
 Silica ................................ 37-40 
 
 Alumina ........................... 1T60 
 
 Peroxide of Iron ................. 27'66 
 
 Protoxide of Iron ................. 12'43 
 
 Magnesia .......................... 0'26 
 
 Potash ............................. 9-20 
 
 Water ................................ 0'60 
 
 99-69 
 
 According to Hague, some of the mica in the granite of the 
 eastern Colorado range is lepidomelane. 
 
 Manganese Spar, Bisilicate of Manganese. 
 Triclinic, and like pyroxene, with a cleavage in three directions, two of 
 which are perpendicular to each other. Usually massive. Lustre vitre- 
 ous. Color light brownish-red, flesh-red, sometimes greenish or yellowish, 
 when impure ; often black outside from exposure. Streak white. Trans- 
 parent opaque. Fracture conchoidal uneven. ^Very tough when mas- 
 sive. H. 5-5 6-5. G.3'4 3-ti8 Composition: 
 
 Silica . ................................ 45-9 
 
 Protoxide of Manganese ......... 51*4 
 
 lOO'O 
 
 Occurs as a gangue of light rose color in the San Juan mines. 
 
56 APPENDIX. 
 
 ALAMANDITE (p. 48). New localities in Chaffee County 
 mentioned by W. B. Smith. Dodecahedral crystals in chlo- 
 ritic schist from Longfellow gulch. Crystals in limestone, 
 having the dodecahedron and trapezohedron about equally 
 developed, from Calumet. 
 
 CINNABAR is said to be found near Durango, but needs 
 verification. 
 
 BNARGITE (p. 13). Occurs massive and in slender crystals 
 in the Missouri mine, Hall Valley, Park County. Small 
 masses in the Centennial mine, Georgetown. In considerable 
 quantity in the Forest Queen mine, Gunnison County, and in 
 the mines of Red Mountain district, San Juan. 
 
 GRAPHITE (p. 27). A large deposit a few miles south of 
 the El Moro coal banks, Las An i mas County. 
 
 NATIVE SULPHUR (p. 6). Abundant in the Spirit mine at 
 Red Cliff. 
 
 PETROLEUM (p. 47). Has been found on Green River. 
 
 TENNANTITE (p. 8). In large quantities in the Red Moun- 
 tain mines, San Juan. 
 
 TORBERNITE (p. 44). Occurs on Lyden Creek (Berthoud), 
 
 Oxide of Lead. 
 
 Occurs pulverulent, occasionally exhibiting, under the microscope, cryw- 
 talline scales. Lustre faint greasy, or dull. Color vivid red, mixed with 
 yellow. Streak orange-yellow. Opaque. H. 2 3. G 4'6. Composition; 
 
 Oxygen .............................. 9'34 
 
 Lead ............................. ..... 90'66 
 
 100-00 
 
 Prof. Emmons mentions its occurrence in some of the mines 
 at Leadville. 
 
 Monoclinic ; primary form a right rhombic prism. Occurs in attached 
 crystals and in layers and granular masses, frequently in a globular form. 
 Lustre vitreous; pearly on planes of cleavage. Color various shades of 
 white, passing into red, gray and brown. Streak white. Transparent 
 subtranslucent. Fracture subconchoidal, uneven. Brittle. H. 3'5 4, 
 G. 2'2. Composition: 
 
 Silica ................................. 59-1 
 
 Alumina ............................. 16'9 
 
 Lime ................................. 9'2 
 
 Water ................................. 14'8 
 
 Occurs in small white glassy crystals in the augite-andesite 
 on Green Mountain, Jefferson County. 
 
APPENDIX. 57 
 
 Monoclinic; priuuiry form a right rhombic prism. Occurs in attached 
 crystals and in layers and granular masses, frequently in a globular form. 
 Lustre vitreous ; pearly on planes of cleavage. Color various shades of 
 white, passing into red, gray and brown. Streak white. Transparent 
 subtranslucent. Fracture subconchoidal, uneven. Brittle. H. 3'5 4. 
 G. 2'2. Composition: 
 
 Silica ................................. 59-1 
 
 Alumina ............................. 16'9 
 
 Lime ................................. 9'2 
 
 Water ................................. 14'8 
 
 100-0 
 
 Occurs in small white glassy crystals in the augite-andesite 
 on Green Mountain, Jefferson County. 
 
 Carbonate of Strontian. 
 Orthorhombic; primary form a right rhombic prism ; occurs crystallized 
 in hexahedral prisms, which are modified on the edges, or terminated by 
 pyramids; often acicular and in divergent groups; also occurs in column- 
 ar-globular forms, fibrous and granular. Lustre vitreous, inclining to res- 
 inons on uneven faces of fracture. Color pale asparagus-green, apple- 
 green, also white, gray, yeilow, and yellowish-brown. Streak white. 
 Transparent translucent. Fracture uneven. Brittle. H. 8'5 4. G. 
 3'605 3'713. Composition: 
 
 Carbonic Acid .................... 29'8 
 
 Strontia .............................. 70'2 
 
 100-0 
 
 Occurs in the shape of small balls on celestite from the 
 the Garden of the Gods. 
 
 SXROMEYERITE. Sulphuret of Silver and Copper. 
 
 Orthorhombic ; isornorphous with copper glance. Usually massive. Lus- 
 tre metallic. Color dark steel-gray. Streak shining. Brittle. Fracture 
 subconchoidal. H. 2'5 3. G. 6'2 6.3. Composition, silver, sulphur and 
 copper in variable proportions. Partial analyses of strorneyerite from Col- 
 orado mines returned the following : 
 
 Ag. Cu. S. Fe. 
 
 Little Giant mine, Clear Creek Co 50'00 21'00 16'60 3'40 W.C. Minger. 
 
 " " 48-00 35-00 16-00 K. Neuman. 
 
 Grant mine, Boulder County 38'00 29'00 F. Graham. 
 
 Winning Card mine, Summit Co.. 49*00 36'00 IG'OO R. Neuman. 
 
 Occurs in small masses and needle crystals coated with 
 chalcopyrite in the Little Giant mine, Clear Creek County. 
 In considerable quanty in the Grant mine, Boulder County, 
 and in the Winning Card and Black Prince mines, Summit 
 County. A variety carrying i y 2 p. c. silver "is found in small 
 quantities in a lode on Saxon Mountain, Georgetown. 
 
 RHODOCHROSITE (p. 10.) Crystallized and fibrous in the 
 Queen of the West mine, near Gray's Peak, associated with 
 alabandite. 
 
58 APPENDIX. 
 
 Oxide of Titanium. 
 Tetragonal ; occurs in four or eight-sided prisms, terminated by pyramids, 
 either single or geniculated, and often striated longitudinally ; also in 
 reticulated masses formed by acicular and capillary rnacled crystals; also 
 massive and imbedded. Sttncture lamalJar. Color reddish-brown, pass- 
 ing into red, sometimes yellowish, bluish, violet, black, rarely grass-green. 
 Streak pale brown. Lustre metallic adamantine. Fracture subconchoidal, 
 uneven. Subtransparent opaque. Brittle. H. 6 6'5. G. 4*18 4*25. 
 Composition : Titanic Acid : 
 
 Oxygen ................................. 39 
 
 Titanium .............................. 61 
 
 100 
 
 A small quartz pebble containing red rutile was found in 
 the Platte River at the foot of the mountains. It is in the 
 collection of Whitman Cross. 
 
 COSALITE (p. 13). Analyses: I from the Alaska mine, Ou- 
 ray County, by Genth. II from Ouray County, by Konig: 
 
 i. n. 
 
 Bismuth ........................... 44'95 43'54 
 
 Lead ............................... 28'10 26'77 
 
 Silver .............................. 1'44 T35 
 
 Copper .................... . ........ 8-00 8'22 
 
 Zinc ...... ........................... 0'24 ...... 
 
 Antimony .......................... 0'51 ...... 
 
 Arsenic ............................. 0'04 ...... 
 
 Selenium .......................... trace ...... 
 
 Sulphur ............................. 16-80 16-54 
 
 100-08 96-42 
 
 BEEGERITE (p. 8). Analyses: I from Ouray county, by 
 Konig. II from the Treasure Vault mine, Geneva District, 
 Clear Creek County, by Genth. 
 
 i. n. 
 
 Bismuth ........................... 19'35 19'81 
 
 Lead ................................ 45'87 50'16 
 
 Silver .............................. 9'98 15'40 
 
 Sulphur ........................... 13-37 14'59 
 
 88-57 99-96 
 
 ANNABERGITE (p. 37). Analysis of annabergite from the 
 Gem mine, Silver Cliff, by Genth: 
 
 Arsenic Acid ..................... 36"64 
 
 Oxide of Nickel .................. 32'64 
 
 Oxide of Cobalt .................. O'fO 
 
 Lime .................. ............... 3'51 
 
 Magnesia ........ ......... ..... ..... 374 
 
 Water .............................. 23'94 
 
 100-97 
 
 CUPRITE (p. 40). Very pure in veins near Pine Grove, 
 Platte Canon, associated with chrysocolla. 
 
APPENDIX. 59 
 
 WITXICHENITE. Cupreous Sulphuret of Bismuth. 
 
 Orthorhombic ; occurs massive and disseminated ; also coarse columnar; or 
 an aggregate of imperfect prisms. Cleavage in one vertical direction. 
 Color steel-gray, tin-white, tarnishing pale lead-gray. Streak black. H. 
 3'5. G. 5. Composition : 
 
 Sulphur 19-44 
 
 Bismuth 42'11 
 
 Copper 38-45 
 
 100-00 
 
 According to T. B. Comstock wittichenite is of common 
 occurrence in the mines of San Juan county, and is rich in 
 silver. 
 
 AIKIIVIXE. Acicular Bismuth. Needle Ore. 
 
 Orthorhombic ; occurs in imbedded acicular four or six-sided prisms, in- 
 distinctly terminated, and striated longitudinally. Also massive. Lustre 
 metallic. Color blackish lead gray, with a pale copper-red tarnish. Frac- 
 ture uneven. H. 2 2'5. G. 6'1 6'8. Composition : 
 
 Sulphur 16-7 
 
 Bismuth 36'2 
 
 * Lead 36'1 
 
 Copper 11-0 
 
 100-0 
 
 Occurs in the mines of San Juan County in beautiful crys- 
 tals, and also in the Gladiator mine, Hinsdale county, carry- 
 ing about 5 per cent of silver (T. B. Comstock). 
 
 Orthorhombic; crystals often tabular; also massive and amorphous. Lus- 
 tre submetallic to vitreous and greasy. Color black, brown, brownish-yel- 
 low, straw-yellow. Streak gray to colorless. Opaque to subtranslucent. 
 Fracture small conchoidal to granular. H. 5 5'5. G. 5*4 5*9. Compo- 
 sition : 
 
 Tantalic Acid ....................... 62'5 
 
 Yttria ................................. 22'6 
 
 Lime ................................... 5'2 
 
 Protoxide of Iron .................. 3'4 
 
 Protoxide of Uranium ........... 6'3 
 
 100-0 
 
 W. B. Smith mentions the occurrence of a black variety, 
 in small masses, at Devil's Head Mountain, Douglas County. 
 
 WAD. Bog Manganese. 
 
 Occurs in amorphous and reniform masses, either earthy or compact, and 
 sometimes incrusting or as stains. Often loosely aggregated, and feeling 
 very light to the hands. Color dull black, bluish or brownish-black. H. 
 0'5. G. 3 4'26. Composition, oxide of manganese, but mixed with 
 other ingredients. 
 
 Occurs in small quantities in many localities throughout 
 the state, frequently staining the rocks black at the surface of 
 veins, and sometimes forming beautiful dendritic specimens, 
 called ' 'forest rock. ' ' Quite a large deposit near the springs 
 on Snake River, Summit County. 
 
60 APPENDIX. 
 
 MYPERSXMEXE. Metalloidal Diallage. Labrador Hornblende. 
 
 Orthorhombic; occurs in foliated masses or imbedded in rocks. Lustre 
 somewhat pearly on a cleavage face, sometimes metalloidal. Color dark 
 brownish-green, grayish-black, pinchbeck-brown. Streak grayish, brown- 
 ish-gray. Translucent to nearly opaque. Brittle. H. 5 6. G. 3'392. 
 Analyses of hypersthene from Buffalo Peaks, Mosquito Range, by Hille- 
 brand : 
 
 Silica 51703 5M57 50'043 
 
 Alumina 1'720 2'154 2'906 
 
 Sesquioxide of Iron 0'304 
 
 Protoxide of Iron 17'995 18'360 J.7'812 
 
 Protoxide of Manganese.. 0'363 0'363 0'120 
 
 Lime 2*873 3'812 6'696 
 
 Magnesia 25'091 24'251 21'744 
 
 Soda 0-274 
 
 100-049 100-097 99*595 
 
 One of the essential constituents of the andesite and tufa 
 rocks of Buffalo Peaks, Mosquito Range. 
 
 PYROXENE. 
 
 Monoclinic ; primary form an oblique rhombic prism ; generally occurs in 
 short, thick crystals, and often in twins ; also amorphous, coarsely lami- 
 nar, granular and fibrous, fibres often fine and long. Lustre vitreous in- 
 clining to resinous, ^sometimes- pearly. Color green of various shades, 
 verging on one side to white or grayish-white, and on the other to brown 
 or black, Streak white to gray and grayish-green. Fracture conchoidal, 
 uneven. Brittle. H. 56. G. 3'23 3'5. Composition : Bisilicate of 
 various bases, the bases being lime, magnesia, protoxide of iron, protoxide 
 of manganese, and sometimes potash and soda. 
 
 Next to the feldspars, pyroxene is the most universal con- 
 stituent of the igneous rocks of the mountains. 
 
 PYROI*USITE. Gray Oxide of Manganese. 
 
 Orthorhombic; occurs crystallized, but generally in botryoidal and reni- 
 form masses, with a radiating, fibrous or columnar structure ; or in granu- 
 lar masses. Often soils. Lustre metallic. Color iron-black, dark steel- 
 gray, sometimes bluish. Streak black or bluish-black, sametimes subme- 
 tallic. Rather brittle. H. 2 5'5. G. 4'82. Composition : 
 
 Manganese 63'3 
 
 Oxigen 36'7 
 
 100-00 
 
 Peale mentions its occurrence on Silver Heels Mountain, 
 near Fairplay, and in the San Juan country. 
 
 Orthorhombic; primary form a right rhombic prism; occasionally hemi- 
 hedial; occurs in columnar crystals striated vertically ; also fibrous and 
 massive, or radiating; sometimes granular. Lustre submetallic. Color 
 dark steel-gray, iron-black. Streak reddish-brown, sometimes nearly 
 black. Opaque ; minute splinters sometimes brown by transmitted light. 
 Fracture uneven. H. 4. G. 4'2 4'4, Composition : 
 
 Sesquioxide of Manganese ...... 89"8 
 
 Water ................................. 10'2 
 
 100-0 
 
 W. B. Smith reports its occurrence in small masses in the 
 region of Devil's Head Mountain, Douglas County. 
 
APPENDIX. 6l 
 
 ARGENXOBISMUXIXE. 
 
 F. A. Genth gives the following analysis of argentobismutite from Lake 
 City, Hiusdale County : 
 
 Sulphur ............................. 16.66 
 
 Bismuth ............................. 52.89 
 
 Silver .............................. 26.39 
 
 Lead ................................ 406100.00 
 
 Antimonial Lead Ore. 
 Orthorhombic; occurs crystallized in modified rectangular prisms, often 
 cruciform or compounded into shapes like a cog-wheel. Also massive, 
 granular compact. Lustre metallic. Color and slreak steel-gray, inclin- 
 ing to blackish lead gray or iron black. Opaque. Fracture conchoidal or 
 uneven. Brittle. H. 2.5 3. G. 5.7 5.9. Composition: 
 
 Sulphur .............................. 19.7 
 
 Antimony ........................... 25.0 
 
 Lead ..... .* ............................. 42.4 
 
 Copper .............................. 12.9100.00 
 
 M. C. Ihlseng mentions the common occurrence of this min- 
 eral in the lodes of Bear and Anvil Mountains, San Juan 
 County. Its associate mineral is galena. 
 
 Asbestus (p. 30) of an olive-green color. Fibres usually coarse and stiff. 
 
 Needle-like fibres an inch or more in length in clear quartz 
 crystals near Calumet, Chaffee County. 
 
 A natural alloy of gold and silver in the proportion of two of gold to one 
 
 of silver, or, 
 
 Gold .................................... 65 
 
 Silver ......... . ........ . ................ 35100 
 
 Color pale yellow to yellowish-white. Known crystals tabular, and im- 
 
 perfect cubes. G. 14 to 17. 
 
 According to P. H. VanDiest the ore in the Nelly mine, 
 San Miguel County, is crystallized electrum. 
 
 Copperas. Green Vitriol. Sulphate of Iron. 
 Monoclinic; in acute rhombic prisms. Occurs massive, pulverulent, bo- 
 tryoidal, reniform, stalactitic and crystallized. Lustre vitreous. Color 
 various shades of green, passing into white; becoming yellowish-white on 
 exposure. Subtransjtarent to translucent. Taste sweetish, astringent, and 
 metallic. Fracture conchoidal. Brittle. H.2. G. 1.832. Composition: 
 Sulphuric Acid ..................... 28.8 
 
 Protoxyd ol Iron .................. 25.9 
 
 Water.". ............................... 45.3100.0 
 
 Proceeds from the decomposition of pyrite in the Black 
 Iron and other mines around Red Cliff; clear green crystals 
 and large masses. Crystals and small masses in the Pennsyl- 
 vania mine, Peru District, Summit County. 
 
 NATIVE CHARCOAL,. 
 
 F. F. Chishelm mentions the occurrence of native charcoal 
 in considerable quantities in the anthracite on the head of 
 Elk Head Creek in Routt County. According to Chisolm it 
 is of common occurrence in Colorado lignites. Charcoal is 
 found at various depths in the Bassick mine, Custer County. 
 
62 APPENDIX. 
 
 AMJNITB. Alumstone. 
 
 Khornbohedral ; crystals modifications of an obtuse rhomboid. Massive, 
 having a fibrous, granular, or impalpable texture. Lustre of crystals vit- 
 reous, or a little pearly on the basal plane. Color white, grayish or red- 
 dish. Streak white. Transparent subtranslucent. Fracture, flat conch- 
 oidal, uneven ; of massive varieties splintery ; sometimes earthy. Brittle. 
 H. 3 54. G. 2.582-752. Composition : " 
 
 Sulphuric Acid ................... 38.53 
 
 Alumina ........................... 37.13 
 
 Potash .............................. 11.34 
 
 Water ................................ 13.00100.00 
 
 S. F. Emmons mentions its occurrence in the Iron mine at 
 Leadville. Probably occurs at a number of places along the 
 foot-hills with native alum. 
 
 SIDEROPHYULITE. (New). Black Mica. If. C. Lewis, Proc. Ac. 
 
 Nat. Sc Phila., 1880. 
 
 Color black; by transmitted light chrome green. Brittle. Analysis: 
 Silica ................................ 36.68 
 
 Alumina ........................... 20.41 
 
 Sesquioxyd of Iron ............. 1.55 
 
 Protoxyd of Iron ................. 25.50 
 
 Protoxyd of Manganese ........ 2.10 
 
 Magnesia ........................... 1.14 
 
 Lime ................................. 0.81 
 
 Soda ................................ 1.09 
 
 Lithia .............................. 0.37 
 
 Potassa .............................. 9.20 
 
 Water ............................... 1.0199.86 
 
 Found in the Pike's Peak region. 
 
 (New). Telluride of Iron. C. U. Shepard, Contri- 
 butions to Mineralogy, 1877. 
 Color silver-white. Analysis by Edmond Fuchs : 
 
 Gold .............................. 5.228 
 
 Silver ............................. 4.198 
 
 Tellurium ........................ 19.650 
 
 Iron ................................ 70.624 
 
 Sulphur ........................... trace 99.700 
 
 Occurs in the Grand View and Phil Sheridan mines, Sun- 
 shine, Boulder County. 
 
 URACOXIXE. Sulphate of Uranium. 
 
 Amorphous, earthy, or scaly, and of fine lemon-yellow color, or orange. 
 Composition : 
 
 Sulphuric Acid .................... 10.16 
 
 Sesquioxyd of Uranium ........ 66.05 
 
 Sesquioxyd of Iron .............. 0.86 
 
 Lime ................................. 2.62 
 
 Water ................................ 20.0699.76 
 
 In the Wood lode, Leavenworth Gulch, near Central City, 
 with pitchblende. 
 
 STIBNITE (p. 23). Large veins ol sulphide of antimony be- 
 tween Troublesome Creek and Lost Lake in Grand County. 
 Float masses of stibnite and quartz are found two or more feet 
 in thickness. 
 
APPENDIX. 63 
 
 ANGLESITE (p. 7). Occurs as the oxidation product of 
 galena in the mines around Red Cliff. It is abundant in the 
 form of minute crystals, or "sand." Emmons. 
 
 ANTHRACITE (p. 47). True anthracite is found on the head 
 of Elk Head Creek in Routt Co. F. F. Chisolm, who exam- 
 ined the field, says there are three veins, the upper four feet 
 thick, the second three and one half feet and the third one 
 foot in thickness. Analyses from the two upper veins : 
 
 Sulphur 0.79 0.44 
 
 Moisture 1,02 2.50 
 
 Volatile matter 9.66 3.20 
 
 Fixed Carbon 83.50 88.20 
 
 Ash 5.82 6.10 
 
 CALAMINE v. 27). Abundant and crystallized in the Sun- 
 nyside mine, San Juan County. Ihlseng. 
 
 GADOLINITE. Massive in the upper canon of the South 
 Platte River. 
 
 JAROSITE (p. 7). Minute but perfect crystals in the Black 
 Iron mine near Red Cliff. Emmons. 
 
 LIMONITE (p. 33). Pseudomorphs after pyrite in the Nelly 
 mine, San Miguel County. 
 
 MOLYBDENITE (p. 25). Common in the lodes on Cement 
 Creek and near Chattanooga, San Juan County. Ihlseng. 
 
 PHENACITE (p. 7). Occurs in prismatic crystals on aqua- 
 marine on Mt. Antero in Chaffee County, and is thought to 
 be the decomposition product of beryl. 
 
 RUTILE (p. 58). W. B. Smith found black ferriferous 
 rutile on St. Peter's Dome, El Paso County. 
 
 GARNET (p. 33. ) Dr. Konig publishes the following analy- 
 sis of a massive titaniferous garnet from southern Colorado, 
 and comments on its relation to schorl omite: 
 
 Silica 30-71 
 
 Titanic Acid 8'11 
 
 Alumina 2'20 
 
 Sesquioxide of Iron 23'20 
 
 Lime 31 '40 
 
 Magnesia T22 
 
 Protoxide of Manganese 0' 46 99.98 
 
 PYRITE (p. 42) Octahedral crystals on Mount Richard 
 Owen, Anthracite Creek, Gunnison County. 
 
 CHRYSOCOLLA (p. 29). Occurs near Pine Grove, in Platte 
 Canon, associated with red oxide of copper. 
 
 BISMUTHINITE (p. 9). Occurs in the mines of San Juan 
 County. 
 
64 APPENDIX. 
 
 CORUNDUM. Emery. Blue, Sapphire. Red, Ruby. 
 
 Rhornbohedral ; commonly occurs crystallized in six-sided prisms ; also in 
 obtuse and acute hexahedral pyramids; cleavage basal, sometimes perfect, 
 but interrupted. Also massive, granular or impalpable. Lustre vilreous, 
 sometimes pearly in the basal planes, and occasionally exhibiting a bright 
 opalescent star of six rays in the direction of the axis (asteriated sapphire). 
 Color blue, red, yellow, brown, gray and nearly white. Transparent to 
 translucent. Fracture conchoidal. Exceedingly tough when compact. 
 H. 9. G. 3.909 4.19. Composition, pure alumina: 
 
 Oxygen 46.6 
 
 Aluminum 53.4100.0 
 
 W. B. Smith mentions the occurrence of a corundum shist 
 in ChafFee County which contains 35 per cent of corundum. 
 It occurs in thin flat crystals,_ and many of them are true sap- 
 phires. 
 
 SAPPHIRE. Blue Corundum. 
 The blue variety of corundum. 
 
 Thin flat crystals, the largest not more than 5 mm in diam- 
 eter, are quite abundant in the corundum shist from Chaffee 
 County. The crystals are transparent and true sapphires. 
 
 PI^AGIOCI^ASE. Triclinic Feldspar. 
 
 The name for the group of triclinic feldspars, the two prominent cleavage 
 directions of which are oblique to one another. 
 
 The most abundant constituent of the andesite of Buffalo 
 Peaks. W. Cross. 
 
 XMENARDIXE. Anhydrous Sulphate of Soda. 
 
 Orthorhombic: cleavage basal; primary form a right rhombic prism. 
 Occurs in rhombic octahedrons, simple or modified on the summit, aggre- 
 gated in crusts and druses. Color white. Translucent or pellucid. Lus- 
 tre vitreous. Effloresces and becomes covered on the surface with a white 
 powder on exposure to the air. Taste saline. Wholly soluble in distilled 
 water. Refracts doubly. H. 2.5. G. 2.62.73. Analysis : 
 
 Water and organic matter 19.10 
 
 Silica 5.20 
 
 Alumina and oxide of iron 14.40 
 
 Chlorine 2.40 
 
 Sulphuric Acid 25.80 
 
 Lime 8.80 
 
 Magnesia 3.90 
 
 Soda 19.1098.70 
 
 Occurs in quantity at Burdsall's Lake near Morrison. 
 
 ZIRCON (p. 58). Small crystals in the porphyrite of Ten- 
 Mile District, Summit County. W. Cross. 
 
 POLYBASITE (p. 43). The distinguishing silver ore of Up- 
 per San Miguel District and Marshal Basin, San Miguel 
 County. Ihlseng. 
 
 ASBESTUS (p. 30). Beautiful snow-white asbestus is found 
 near Jasper, Rio Grande County. Asbestus is also found in 
 float rock on Arapahoe Peak. 
 
APPENDIX. ^ 65 
 
 DYSCRASIXB. Antimonial Silver. 
 
 Orthorhombic ; occurs in hexagonal prisms and stellate forms ; also mass- 
 ive, disseminated, or in grains. Color and streak between silver-white and 
 tin-white, often tarnished yellow or reddish. Lustre metallic. Easily 
 frangible. Soft and slightly malleable. H. 3.5 4. G. 9.44 9.82. Comp.: 
 
 Silver 78 
 
 Antimony 22 100 
 
 Hills and Endlich mention the occurrence of dyscrasite in 
 the mines of Poughkeepsie Gulch, San Juan county. 
 
 MYDROPMA^B. Variety of Opal. 
 
 Massive, amorphous. Lustre vitreous, frequently subvitreous. Translu- 
 cent. Color whitish, or light colored. Adheres to the tongue and becomes 
 more translucent or transparent in water. Composition : 
 
 Silica 93.00 
 
 Alumina 2.00 
 
 Water 5.00100.00 
 
 A white and nearly opaque variety of hydrophane, in 
 rounded lumps, with a white chalky or glazed coating, is 
 found in the State, but the locality is a secret. When water 
 is dropped upon it, it first becomes very white and chalky, 
 and then gradually perfectly transparent. This property is 
 developed so strikingly that the name "Magic Stone" has 
 been proposed for it, and its use suggested in rings, lockets, 
 charms, etc., to ^conceal photographs, hair or other objects 
 which the wearer wishes to reveal only when his caprice 
 dictates (Kunz\ 
 
 R.IO1SITB. Bismuth-Tetrahedrite. 
 
 Has a conchoidal fracture, an iron-black color, black streak and greasy- 
 metallic lustre. An analysis of the Switzerland mineral gave : 
 
 Sulphur 29'IQ 
 
 Arsenic 11'44 
 
 Antimony 2'19 
 
 Bismuth 13'07 
 
 Copper 37'52 
 
 Silver 0'04 
 
 Iron 6-51 
 
 Cobalt 1-20 101-07 
 
 Abundant in the Yankee Girl mine, Ouray county, carrying 
 about, two per cent of silver. 
 
 ZOR.GI'TB* Seleniuret of Lead and Copper. 
 
 Massive, granular. Lustre metallic. Color dark or light lead-gray, some- 
 times inclining to reddish, and often with a brass-yellow or blue tarnish. 
 Streak darker. Brittle. H. 2'5. G. 7 7 '6. Composition : 
 
 Selenium 34 
 
 Lead 50 
 
 Copper 15 
 
 Silver 1100 
 
 Occurs in quantity in the Pearl lode, Minnesota gulch, San 
 Juan county. 
 
66 t APPENDIX. 
 
 RuTiLE (p. 58). Small jet-black tetragonal crystals occur 
 in quartz gangue near the Eureka tunnel, St. Peter's Dome, 
 El Paso county, associated with arfvedsonate and zircon, and 
 closely resembling in form the latter mineral. An analysis 
 by Eakins gave : 
 
 Titanic Acid 9473 
 
 Oxyd of Iron 3'77 
 
 Silica 1-37 
 
 Water 0'71 10078 
 
 SCHIRMERITE (p. 32). In the Santa Cruz mine, Howard's 
 Fork, San Miguel county, with bismuthinite, chalcopyrite 
 and galena. 
 
 EPIDOTE (p. 36). Good single crystals are found near the 
 Colorado Coal and Iron Go's mine at Calumet. 
 
 ANGLESITE (p. 7). L,arge masses in the Madonna mine, 
 Chaffee county, often as pseudomorph after galena. 
 
 ARSENOPYRITE (p. 40). Near Ruby camp, Gunnison coun- 
 ty. On Mount Wilson, San Miguel county. . 
 
 BORNITE (p. 14). In the Plutus mine, Idaho Springs. In 
 the mines of Red Mountain district, San Juan and Ouray 
 counties. Near Maysville, Chaffee county. Gem mine, Fre- 
 mont county, with niccolite. 
 
 CHALCOCITE (p. 37). Occurs almost alone, in sandstone 
 with matrix of calcite, in San Miguel county. Massive at 
 Ironton, Ouray county. 
 
 HEMATITE (p. 34). Large, irregular deposit in the Breece 
 mine, Leadville. Large beds near Ashcroft and Carbondale, 
 Pitkin county. 
 
 STROMEYERITE (p. 57). Rarely in the Plutus mine, Idaho 
 Springs. In quantity in the Yankee Girl mine, Ouray Co. 
 
 TENNANTITE (p. 8). Frank Hough mine, Hinsdale Co. 
 
 GRAPHITE (p. 27). In quartz veins 2^2 feet thick on 
 branches of Quartz Creek, Gunnison county. 
 
 MAGNETITE (p. 34). Grayback gulch, Costilla county. 
 Titaniferous variety on Iron mountain, Fremont county. 
 Both worked by the Colorado Coal and Iron Company. A 
 pure magnetite in large quantity on Cebolla Creek, and titan- 
 iferous magnetite near Snowmass mountain, Gunnison county. 
 In quantity near Hamilton, Park county. Near Ashcroft and 
 Carbondale, Pitkin county. 
 
 AcTiNOUTE (p. 30). Light green and bluish green actino- 
 lite is found on Mt. Ouray, Chaffee County. 
 
APPENDIX. 67 
 
 NATIVE SULPHUR (p. 6). In the Queen of the West mine, 
 Peru District, Summit County, with alabandite and rhodo- 
 chrosite. In the S. S. mines, Park County. In Routt Co., 
 but the exact locality is not known. In the Mineral Chief 
 lode, Georgetown, with galena. 
 
 RHODOCHROSITE (p. 10). Rich red, transparent crystals 
 in the John Reed mine at Alicante, Lake county. Some 
 cleavage pieces are as pellucid as Iceland spar and show the 
 same strong double refraction. It also occurs opaque, mass- 
 ive and cleavable, enclosing bright cubic crystals of pyrite. 
 Analysis by James B. Macintosh gave : 
 
 Protoxyd of Manganese 58.325 
 
 Protoxyd of Iron 3.615 
 
 Carbonic Acid (by difference) 38.06 100.00 
 
 At the Ule mine, Lake City, opaque flesh-colored crystals, 
 rounded and curved like dolomite, are found on galena. 
 Large masses of white, yellowish and light pink color as 
 stalagmites in the Stevens mine, near Gray's Peak. 
 
 HYALITE (p. 41). Crusts on the hypersthene-andesite of 
 Buffalo Peaks, Chaffee county. 
 
 SCHEELITE (p. 27). In crystals in some of the mines of 
 Baker Park, San Juan county. (EndlicJi). 
 
 CUPRITE (p. 40). Sweet Home mine, Buckskin, Park Co. 
 North Fork of the Poudre, Larimer county, with native cop- 
 per and chalcocite. 
 
 CELESTITE (p. 25). On Apishapa Creek. 
 HESSITE (p. 28). Mines of Red Cliff, Eagle county. Oc- 
 casionally met with in the mines of La Plata county. 
 
 PETZITE (p. 43). Hotchkiss mine, Hinsdale county. 
 
 SYLVANITE (p. 32). In quartz veins on Junction Creek, 
 and at the head of the Rio la Plata, La Plata county. 
 
 APOPHYLLITE (p. 15). Endlich mentions its occurrence on 
 Hunt's Peak, Fremont county. 
 
 BISMUTHENITE (p. 9). Near Silverton, in long steel-blue 
 and iridescent needles, associated with hubnerite, tetrahedrite 
 and drusy quartz. 
 
 OPAL (p. 40). Nodules of milk-white opal, some having 
 moss-like markings, on Badger Creek, South Park. 
 
 FLUORITE (p. 10). In veins with quartz in Poughkeepsie 
 gulch, San Juan county. On Kelso mountain, Clear Creek 
 county. 
 
 CHRYSOCOLLA (p. 29). In the Sangre de Christo moun- 
 tains, Custer and Saguache counties. 
 
68 APPENDIX. 
 
 Penjield, Am. Jr. Sc. t July, 1888. 
 Monoclinic ; crystals generally tabular in habit, transparent, colorless or 
 slightly yellowish. Lustre vitreous. H. 6 7. G. 2'598. Analysis of 
 Colorado mineral gave : 
 
 Silica .................... ............. 51.8 
 
 Glucina ... ........................... 39.6 
 
 Lime ................................. 1.0 
 
 Water ................................ 8.4100.8 
 
 Found on Mt. Antero, Chaffee county, with phenacite, or- 
 thoclase, beryl, muscovite and fluorite. Occurs in small thin 
 rectangular blades attached to quartz, and having the shape of 
 a thin slice cut from the side of a cylinder parallel to its axis. 
 
 PYRR.HOXIXE. Magnetic Iron Pyrites. 
 
 Hexagonal ; commonly massive and amorphous ; structure granular. Lus- 
 tre metallic. Color between bronze-yellow and copper- red, and subject to 
 speedy tarnish. Streak dark grayish-black. Brittle. Magnetic, being 
 attractable in fine powder by a magnet, eyen when not affecting an ordi- 
 nary needle. H. 3'5 4'5. G. 4'4 4.68. Composition : 
 Sulphur .............................. 39'5 
 
 Iron ................................... 60-5 100-0 
 
 Occurs in small quantity in the lodes of Needle mountains, 
 San Juan county. 
 
 SPHBROSIDBRITB. Concretionary Siderite. Carbonate of Iron. 
 
 In globnlar concretions, either solid or concentric scaly, with usually a 
 
 fibrous structure. Composition : 
 
 Carbonic Acid ....................... 37'9 
 
 Protoxyd of Iron.- ................ 62'1 lOO'O 
 
 A thin seam of spherosiderite occurs above the coal of the 
 Laramie formation in many parts of the state. In some places 
 it has weathered out in nodules, which are found upon the 
 plains in great quantity. It is found near Trinidad and El 
 Moro in Las Animas county, Walsenburgh in Huerfano coun- 
 ty, and Marshall in Boulder county. 
 
 H VmtOPIIAXK. Variety of Opal. 
 
 Massive, amorphous. Lustre vitreous, frequently subvitreous. Translu- 
 cent. Color whitish, or light colored. Adheres to the tongue and becomes 
 more translucent or transparent in water. Composition : 
 Silica .......................................... 93.00 
 
 Alumina ...................................... 2.00 
 
 Water ......................................... 5.00100.00 
 
 A white and nearly opaque variety of hydrophane, in 
 rounded lumps, with a white chalky or glazed coating, is 
 found in the State, but the locality is a secret. When water 
 is dropped upon it, it first becomes very white and chalky, 
 and then gradually perfectly transparent. This property is 
 developed so strikingly that the name u Magic Stone" has 
 been proposed for it, and its use suggested in rings, lockets, 
 charms, etc., to conceal photographs, hair or other objects 
 which the wearer wishes to reveal only when his caprice 
 dictates (Kunz\ 
 
APPENDIX. 69 
 
 SAMARSKIXB. Hillebrand, Proc. Col Sc. Soc,, 1888. 
 
 Orthorhornbic. Lustre of surface of fracture shining and submetallic. 
 
 Color velvet-black. Streak dark reddish-brown. Opaque. Fracture sub- 
 
 conchoidal. H. 5.56. G. 5.6145.69. 
 
 Occurs in granitic debris on Devil's Head Mountain, Dong- 
 las County, in fragments of all sizes up to that of a chestnut, 
 without crystal form. The following analysis by Hillebrand 
 shows the composition: 
 
 Tantalic Acid 27.03 
 
 Columbic Acid 27.77 
 
 Tungstic Acid 2.25 
 
 Oxide of Tin 0.95 
 
 Zifconia 2.29 
 
 Protoxyd of Uranium 4.02 
 
 Thoria 3.64 
 
 Protoxyd of Cerium 0.54 
 
 Oxide of Didymium and Lanthanum... 1.80 
 
 Oxide of Erbium 10.71 
 
 Yttria 6.41 
 
 Sesquloxyd of Iron 8.77 
 
 Protoxyd of Iron 0.32 
 
 Protoxyd of Manganese 0.78 
 
 Zirconia 0.05 
 
 Oxide of Lead 0.72 
 
 Lime 0.27 
 
 Potassa 0.17 
 
 S'-da and Lithia 0.25 
 
 Water 1.58 
 
 100.31 
 MEGABASITE. Tungstate of Manganese. 
 
 Orthorhombic ; usually occurs in fine needles. Lustre vitreous, a little 
 adamantine. Color brownish-red, clover- brown to yellowish-brown, with 
 a reddish-brown to hyacinth-red translucency. Streak pale yellowish- 
 brown to ochre-yellow. H. 3.5 4. G. 6.45. 
 
 H. F. Keller gives the following analysis of megabasite 
 from Bonita Mountain, near Silverton: 
 
 Tungstic Acid 74.24 
 
 Oxide of Manganese 21.09 
 
 Protoxyd of Iron 2.06 
 
 Oxide of Copper 0.11 
 
 Oxide of Manganese trace. 
 
 Silica 2.13 
 
 99.63 
 
 Lime-Aluminagarnet. 
 A cinnamon-colored variety of garnet. Composition : 
 
 Silica 41 
 
 Alumina 23 
 
 Oxide of Iron 4 
 
 Lime 32100 
 
 Longfellow gulch, ChafFee county, in dark rhombic dodeca- 
 hedrons, disseminated through chloritic schist. In metamor- 
 phosed limestone near Calumet. They have finely polished 
 faces and beautiful clear color. 
 
70 APPENDIX. 
 
 WARREBJIXE. (New.) Sulphantimonate of Lead. L. G. Eakins, Proc- 
 
 Col. Sc. Soc., 1888. 
 
 Small acicular crystals forming matted wooly-like masses. Color grayish- 
 
 black, occasionally iridescent. Analysis by Eakins: 
 
 Lead ............................................ 39.33 
 
 Antimony ...................................... 36.34 
 
 Iron ............................................. 1.77 
 
 Silver, Copper, Manganese .- ............. trace. 
 
 Sulphur .............. .......................... 21.19 
 
 Insoluble gangue .............................. 52 
 
 99.15 
 
 Found in the Domingo lode, on the ridge between Canon 
 and Baxter Basin, Gunnison county. Named after E. R. 
 Warren of Crested Butte. 
 
 Sulphuret of Silver and Antimony. Eakins, 
 Proc. Col. Sc. Soc., 1888. 
 
 Monoclinic; occurs in small, deeply striated prisms. Lustre metallic. 
 Color and streak light steel gray, inclining to silver white, also blackish 
 lead gray. Yields easily to the knife, and is rather brittle. Fracture sub- 
 conchoidal uneven. H. 2 2.5. G. 6 6.4. Comp.: Sulphur 18.6, anti- 
 mony 25.9, lead 31.2, silver 24.3. 100. Silver often replaced by lead. 
 
 Occurs in a mine on Augusta Mountain, Gunnison Co. , in 
 silicious gangue together with pyrite and sphalerite, and 
 forms groups of acicular crystals which are elongated prisms, 
 deeply striated, but too small to be measured. The analysis 
 is as follows: 
 
 Silver....: ...................................... . trace. 
 
 Lead ............................................. 55.52 
 
 Iron ............................................. trace. 
 
 Antimony ................. . .................... 25.99 
 
 Sulphur (calculated) ........................ J8.98 
 
 100.40 
 
 ENARGITE (p. 13). In the mines of Summit district, Rio 
 Grande county. 
 
 JET (p. 45). On the Trinchera mesa, southeast Colorado. 
 
 Moss AGATE (p. 18). In nodules on Badger Creek, South 
 Park. 
 
 ORTHOCLASE (p. 12). Excellent crystals are found in the 
 slide rock just above the river on Crested Butte Mountain, 
 Gunnison County. 
 
 AMETHYST (p. 23). Pale colored amethyst is found on Car- 
 nero Creek, Saguache County. In form they are quite re- 
 markable, the prismatic faces being enormously large, while 
 the terminal pyramidal faces are very minute. "Phantom 
 crystals" are often enclosed, and occasionally liquid inclu- 
 sions with movable bubbles. 
 
CLEAR CREEK COUNTY MINERALS. 
 
 Clear Creek County is pre-eminently mineral-bearing, the 
 only tillable land being a few rods in width along the streams. 
 The southeastern portion of the county, however, is valuable 
 only for timber, as mineral veins in that region either do not 
 exist or have not been discovered. The formation is archean, 
 veined with dikes of eruptive rocks, in which porphyry pre- 
 dominates. Heavy-bedded and thinly-laminated gneiss, red 
 and gray granite, schist, syenite, felsitic and hornblendic 
 rocks pass by imperceptible phases from one to the other in 
 inextricable confusion, and the dip of the rocks are as variable 
 as their structural character. 
 
 It is somewhat remarkable that so few accessory minerals 
 have been found in the granite and kindred rocks, and equal- 
 ly remarkable that the minerals found in the veins are locally 
 few in variety and seldom crystallized. Taken as a whole, 
 however, Colorado is probably the richest in variety of min- 
 erals of any known region. But the number of local miner- 
 als might be materially increased were the finders as much 
 interested in learning the nature of the minerals that pass 
 through their hands as in determining their gold and silver 
 value. The following minerals are found in Clear Creek 
 Coiinty : 
 
 Acanthite (orthorhombic silver glance). A few small 
 crystals were found in a lot of polybasite crystals from the 
 Emma mine. 
 
 Albite (soda feldspar). A constituent of some of the gran- 
 itic rocks, particularly on Fall River. 
 
 Amethyst. r-A few specimens of good color have been 
 found in a lode near Dumont and on Chicago Creek. 
 
 Anglesite (sulphate of lead). Aggregations of small crys- 
 tals in the Freeland mine. Small crystalline masses in the 
 Troy mine, Georgetown, intimately associated with cerussite. 
 
 Aragonite (carbonate of lime). Large beautiful specimens 
 of coralloidal form were found in the Marshall tunnel a num- 
 ber of years ago. A shaft near the Argentine lode, on Leav- 
 enworth Mountain, furnishes yellow tinted specimens. 
 
2 Clear Creek County Minerals. 
 
 Argentite (silver glance). In small quantities in nearly 
 all the silver mines. Masses weighing two to three pounds 
 have been found in the Colorado Central and Saxon mines. 
 Crystals rare and quite .small. 
 
 Arsenopyrite (arsenical pyrites). Occasionally found in 
 the veins about Empire, Idaho and in Geneva District. 
 
 Autunite (phosphate of uranium and lime). Small green- 
 ish-yellow tabular crystals in the Peabody lode, near George- 
 town, and in a lode on Chicago Creek. 
 
 Azurite (blue carbonate of copper.) Occurs as an incrus- 
 tation near the surface of many of the lodes. 
 
 Barite (heavy spar). Of frequent occurrence in some of 
 the veins. Clusters of amber-colored crystals in the 7:30 
 mine. In the Little Giant mine in thin white crystals. Small 
 tabular crystals in the Oneida and many other lodes. 
 
 Biotite (black mica). A constituent of much of the gran- 
 ite and eruptive rocks. 
 
 Bornite (purple copper ore). Of frequent occurrence in the 
 gold mines. Handsome specimens in the Neath. 
 
 Calcite (carbonate of lime). Occurs in small quantities 
 in many of the mines. Nail-head crystals in the Terrible. 
 
 Cerargyrite (horn silver, chloride of silver.) Thin crusts 
 on the surface ores from some of the lodes on Democrat and 
 Lincoln Mountains. 
 
 Chalcanthite (blue vitriol). Forms on the walls of the 
 Whale Tunnel, near Idaho. 
 
 Chalcedony. Beautiful botryoidal specimens have been 
 found in the mines at Idaho. Occasionally met with in the 
 Little Giant and other veins. 
 
 Chalcopyrite (copper pyrites). Of general occurrence but 
 in less quantity than pyrite, and carries more gold and 
 silver. A few fine crystals., usually studded with minute crys- 
 tals of tennantite, have been found in the Freeland mine. 
 
 Chrysocolla (silicate of copper). In the Champion lode, 
 near Idaho. 
 
 Dolomite (magnesian limestone). Of frequent occurrence 
 in the veins in Ohio District. Occasionally found in other 
 lodes. 
 
 Enargite (arsenical sulphide of copper). A small amount 
 is found in the surface ores of the Centennial mine, associated 
 with native copper. 
 
Clear Creek County Minerals. j 
 
 Epidote. Massive and crystallized in the granitic rocks 
 between Georgetown and Green Lake. Very good crystal on 
 Floyd Hill. 
 
 Fibrolite. Inferior fibrolite of a grayish-green color oc- 
 curs in the granite on Sherman Mountain. 
 
 Fire Opal. A very handsome opal showing bluish and 
 yellowish flames, and greatly resembling sofhe Mexican opals, 
 is found in a felsite rock in Gilson Gulch, near Idaho. 
 
 Fluorite (fluor spar). Impure massive fluorite of deep 
 purple color is found in some of the lodes on McCJellan Mt. 
 
 Galenite. The most abundant mineral in the silver mines. 
 Good crystals in the Dunderberg, Terrible and Little Giant 
 mines. In many of the mines it occurs in all grades from 
 coarse cubes to extremely fine granular, and sometimes lam- 
 ellar. The percentage of silver it carries varies from a few 
 ounces to several hundred ounces per ton. 
 
 Garnet. Large brown garnets are occasionally found im- 
 beded in granite on Griffith Mountain. 
 
 Gibralter Rock. A ledge of this variety of limestone is 
 located near Idaho Springs. When polished it is quite hand- 
 some. 
 
 Hematite. Ocherous hematite is found near the surface 
 of many of the veins. 
 
 Hornblende. Of general occurrence in the granitic rocks. 
 An essential constituent of syenite, and is frequently found 
 massive. No good crystals have been found. 
 
 Hornstone. Of frequent occurrence in the mines, forming 
 part of the gangue rock. 
 
 Kaolinite (porcelain clay). Masses showing crystalline 
 structure in the Silver Mountain lode, near Empire. Occurs 
 in many other lodes in small quantity. 
 
 Linarite (cupreous anglesite). A mineral having the gen- 
 eral characteristics of linarite is found at the surface of some 
 of the lodes on Red Elephant Mountain. 
 
 Magnetite (magnetic iron). Crystals of magnetite are of 
 frequent occurrence in granite. The granite quarried at 
 Brownville is liberally sprinkled with crystals of this mineral. 
 
 Malachite (green carbonate of copper). Occurs as a stain 
 or incrustation at the surface of man of the veins. 
 
 . Found in small quantities at the surface, of the 
 Colorado Central vein. 
 
 
 
 1 /I 
 
4 Clear Creek County Minerals: 
 
 Micaceous Iron (hematite). Quite abundant between Clear 
 Creek and Mill Creek. 
 
 Molybdenite. Small masses in the Louisiana lode, Sher- 
 man Mt. , in the. Colorado Central mine, in the Moline Tun- 
 nel, in several localities on Red Elephant Mt. , and in Daily 
 District. 
 
 Muscovite (corfUnon mica). Common in archean rocks. 
 Sometimes found in large masses. Very good crystals are 
 found in a mica claim near Graymont. 
 
 Native Copper. Small dendritic scales in the Centennial 
 and McClellan mines ; wires and small masses in the Pitts- 
 burg mine, Empire. Loose masses have been found in the 
 soil about Idaho. 
 
 Native Gold. -In placers and in Veins along the creek 
 from Idaho to Empire, on Fall River and in Argentine Dis- 
 trict. Many of the silver mines also carry an appreciable 
 amount of gold. 
 
 Native Silver. In leaf and wire form in many of the mines 
 throughout the county. Nuggets in the talc bed on Fall 
 River. 
 
 Niccolite (arsenical nickel). Occurs sparingly in the Rosa 
 lode, Dumont. 
 
 Orthoclase (common feldspar). One of the most common 
 rocks throughout the county and occurs in immense masses 
 as well as a constituent of nearly all country rock. 
 
 Polybasite. Next to gray copper polybasite is the most 
 abundant rich silver ore found in the county. Crystals are 
 quite abundant in the Emma mine, and some have been 
 found more than an inch in their longest diameter. A few 
 crystals are met with in the Colorado Central. It usually 
 occurs massive, when it is difficult to distinguish from gray 
 copper. 
 
 Proustite (light ruby silver ore). Small masses and mi- 
 nute translucent crystals in the Colorado Central mine. 
 
 Pyrargyrite (dark ruby silver ore). Of general occurrence 
 in the silver mines but usually in small quantity. Probably 
 more is found in the Colorado Central than in any other 
 mine. Crystals have never been noticed. 
 
 Pyrite. Almost universally in the mines. Particularly 
 abundant at Empire and Idaho, and in the "gold belt" lodes 
 at Georgetown. Usually massive ; crystals quite small and 
 rarely vary from the cube. Carries gold and a little silver. 
 
Clear Creek County Minerals. 5 
 
 Pyromorphite (phosphate of lead). Sparingly in some of 
 the mines on Democrat Mountain. 
 
 Quarts. In large masses at the eastern end of the county. 
 Forms part of the gangue rock of the mines. Crystals fre- 
 quent but usually small. 
 
 Rhodochrosite (carbonate of manganese). Some very pretty 
 crystals are found in the Danube lode, near Idaho Springs. 
 
 Rose Quarts. Beautiful rose-tinted masses on Floyd Hill. 
 Crystals in the Little Giant mine. 
 
 Schirmerite (bismuth silver ore). In small masses in the 
 mines of Geneva District. 
 
 Siderite (carbonate of iron). Of frequent occurrence, both 
 massive and crystallized, in the mines in the Trail Creek re- 
 gion. Occasionally in other mines. 
 
 Sphalerite (zinc blende). Abundant, especially in the 
 Georgetown and Silver Plume district. Varies in color from 
 amber to black. Large clusters of black crystals in the Maine 
 mine, some crystals three inches in diameter. Usually car- 
 ries but littje silver. 
 
 Stromeyerite. A variety carrying a little more than one 
 per cent of silver is found in small quantities in the Algon- 
 quin, Silent Friend and other lodes on Saxon Mountain. 
 In large quantities in the Plutus mine, mixed with bornite, 
 and carrying 25 per cent of silver. In small acicular crystals 
 in the Little Giant mine, and carrying about 50 per cent of 
 silver. 
 
 Talc. An extensive bed near the head of Fall River which 
 is being sluiced by the Alice company for the gold it contains. 
 
 Tennantite (arsenical sulphide of copper). Clusters of 
 highly polished crystals from microscopic size to ^ of an inch 
 in diameter in the Freeland mine. 
 
 Tourmaline. Inferior tourmaline is found on Baker Moun- 
 tain and near Green Lake. 
 
 Tetrahedrite (gray copper). The most abundant rich silver 
 ore. Gray copper from 'the mines in the vicinity of George- 
 town and Silver Plume carries as high as 30 per cent of silver, 
 while that from the mines east of Georgetown and in the 
 vicinity of Idaho Springs, and in Geneva District rarely con- 
 tains more than one per cent of silver. A few coarse crystals 
 have been found in the Geneva District mines. 
 
 Uraninite (pitchblende). Small masses have been found 
 in the Jo Reynolds mines. 
 
Gilpin County Minerals, 
 GILPIN COUNTY MINERALS. 
 
 Albite (soda feldspar). A constituent of some of the arch - 
 ean rocks. 
 
 Amethyst. Small beautiful crystals of good color have 
 been found in the gravel in Nevada. 
 
 Arsenopyrite (arsenical pyrites). Occasionally found in 
 small masses in the Kansas, Illinois, Burroughs, California 
 and other mines. 
 
 Azurite (blue carbonate of copper.) Occurs as an incrus- 
 tation or stain at the surface of many of the mines. 
 
 Barite (heavy spar). Of frequent occurrence in some of 
 the mines, and occasionally crystallized. 
 
 v Biotite (black mica). A constituent of much of the gran- 
 ite and eruptive rocks. 
 
 Bornite (purple copper ore). Of general occurrence in the 
 mines in greater or less quantities. Crystals rare. . 
 
 Calcite (carbonate of lime). Occurs in small quantities 
 in many of the mines. 
 
 Chalcanthite (blue vitriol). Near Black Hawk, in a de- 
 posit. In many of the old mine dumps about Central. 
 
 Chalcedony. Small masses occasionally met with in many 
 of the mines. 
 
 Chalcopyrite (copper pyrites). Of general occurrence and 
 one of the principal ores of gold. Crystals frequent. 
 
 Covellite (indigo copper). In grains and as a powder in- 
 Pewabic, Gunnell, Sapp and other lodes near Central. 
 
 Enargite (arsenical sulphide of copper). Massive and finely 
 crystallized in the Powers mine, Russell District. 
 
 Epidote. Massive and crystallized in the granitic rocks 
 throughout the county. 
 
 Float Stone. Snow-white masses showing gold have been 
 taken from the Mammoth mine, Central. 
 
 Fluorite (fluor spar). Met with occasionally in some of 
 the veins. 
 
 Galenite. Abundant in many of the mines. Fine crystal- 
 lized specimens have been found in the Glennan and Running 
 mines, Black Hawk, the Delaware and Calhoun lodes, Rus- 
 sell District, the Mount Desert and Forks lodes at Nevada. 
 Crystal two inches across have been found in the Glennan. 
 
Gilpin County Minerals. j 
 
 Garnet. Iron garnets are quite abundant in the vicinity 
 of Central. 
 
 Hornblende.- Of general occurrence in the archean rocks. 
 
 Hornstone. Of frequent occurrence in the mines, forming 
 part of the gangue rock. 
 
 Kaolinite (porcelain clay). In greater or less abundance 
 in all the mines. 
 
 Magnetite (magnetic iron). Crystals of magnetite are of 
 frequent occurrence in granite. Octahedral crystals on Gun- 
 nell Hill. 
 
 Malachite (green carbonate of copper). Occurs as a stain 
 or incrustation at the surface of many of the veins. 
 
 Melanterite (copperas, green vitriol). In the dumps of 
 many of the old mines. 
 
 Molybdenite. Small masses in the Leavitt lode. 
 
 Muscovite (common mica). Common in archean rocks. 
 Sometimes found in large masses. 
 
 Oligoclase (aveuturine feldspar). A constituent of much of 
 the archean rocks. 
 
 Native Copper. Small dendritic coatings in a number of 
 the lodes. Masses weighing several pounds have been found 
 in the Narraganset and Gregory mines. 
 
 Native Gold. In placers and in the veins. Beautiful mi- 
 crosopic crystals in the Gunnell, Gregory, Bates and other 
 mines. Strings of minute crystals, forming chain-like wires, 
 are frequently found. 
 
 Native Silver. In leaf and wire form in the Coaley and 
 other mines. 
 
 Orthoclase (common feldspar). One of the most common 
 rocks throughout the county and occurs in immense masses 
 as well as a constituent of nearly all of the rocks. Crystals 
 in porphyry on Gregory Hill. 
 
 Pyrite (iron pyrites). Abundant, massive and crystallized, 
 in all the lodes, and composes the greater part of the gold 
 ore. Beautiful crystallized specimens and radiated and bo- 
 tryoidal masses common in many of the mines. Cubes from 
 one to three inches across have been taken from the King- 
 ston, Hill House and S. P. Chase lodes in Russell District. 
 A lode near the head of Virginia Canon has furnished a great 
 many modified crystals. 
 
 Rose Quarts. In small masses in the vicinity of Central 
 and other localities. 
 
8 Gilpin County Minerals. 
 
 Quartz. Common in large masses. Forms part of the 
 gangue rock in the mines. Crystals frequent but usually 
 small. An essential constituent of granitic rocks. 
 
 Siderite (carbonate of iron). Of frequent occurrence, both 
 massive and crystallized, in the mines. 
 
 Rock Crystal. Doubly terminated limpid crystals common 
 in the gravel on Quartz Hill. The crystals are small but 
 quite perfect. 
 
 Sphalerite (zinc blende). Abundant in many of the lodes. 
 Clusters of tetrahedral crystals in the Coaley lode, Black 
 Hawk. Crystallized in the Delaware and Calhoun lodes. 
 
 Talc. In small quantities in nearly all the mines. 
 
 Tourmaline. Black crystals near Nevada. 
 
 Tetrahedrite (gray copper). Not unfrequently found in a 
 number of mines, sometimes crystallized. 
 
 Uraninite (pitchblende). Abundant at one time in the 
 Wood lode, L/eavenworth Gulch. A few imperfect crystals. 
 
 Uraconite. Occurs as a yellow coating on pitchblende in 
 the Wood lode. 
 
 Cerussite (carbonate of lead). Of rare occurrence at the 
 surface of some of the veins. 
 
 Lepidomelane (iron potash mica). A constituent of some of 
 the granite. 
 
 NEEDS VERIFICATION. 
 
 Aurichalcite. Jones lode, near Nevada. 
 
 Allophane. Cincinnati lode. 
 
 Calamine. 
 
 Glockerite. On old dumps. 
 
 Goslarite. Wood lode, Leavenworth Gulch. 
 
 Greenockite. Jones and Dallas lodes. 
 
 Jarosite. Wood lode. 
 
 Lievrite. Below Black Hawk. 
 
 Magnesite. Bobtail, Running and Pewabic lodes. 
 
 Marcasite. 
 
 Native Sulphur. Jones lode, Nevada. 
 
 Plumbogummite. \32ti\as lode, Black Hawk. 
 
 Pyrrhotite. 
 
 Smithsonite. Jones lode, Nevada. 
 
 Uranochalcite. Wood lode. 
 
 Willemite. Jones lode, Nevada. 
 
 Wulfenite. Gunnell Hill. 
 
 Zincite. Jones lode, Nevada. 
 
 Zippeite. Wood lode. 
 
Grand County Minerals. 
 GRAND COUNTY MINERALS. 
 
 Albite (soda feldspar). A constituent of some of the arch- 
 aean rocks. 
 
 Agate. Abundant along Williams River; on the ridge be- 
 tween Hot Sulphur Springs and Corral Creek ; on the moun- 
 tains at the mouth of Willow Creek. 
 
 Agatized Wood. Abundant on the ridges north of Willow 
 Creek. Also between Hot Springs and Corral Creek. 
 
 Argentite (silver glance). In small quantities in the min- 
 eral veins in Campbell district. 
 
 Azurite (blue carbonate of copper.) Occurs as an incrus- 
 tation in copper veins in the Park Range at the head of a fork 
 of the North Plate River. 
 
 Barite (heavy spar). Reported to occur in extensive beds 
 on Vasquez Creek. 
 
 Basanite (touch stone). Sparingly along Willow Creek. 
 
 Biotite (black mica). A constituent of much of the gran- 
 ite and dike rocks of the mountains and eruptive rocks of Mid- 
 dle Park. 
 
 Bismutite (carbonate of bismuth). Found near Cummuns 
 City, North Park. Needs verification. 
 
 Brown Coal (lignite). Extensive veins in North Park and 
 exists at various points on the divide between North and Mid- 
 dle Parks. 
 
 Byerite. A name given to the coal found in Middle Park. 
 It belongs to the class caking bituminous, and resembles al- 
 bertite in the large amount of gas and tarry oil yielded. It 
 melts and intumesces when heated. 
 
 Carnelian. Sparingly on the ridge south of Willow Creek. 
 
 Cerussite (carbonate of lead). Frequently found in small 
 masses near the surface of mineral veins. 
 
 Chalcedony. Abundant on the ridges on both sides of 
 Willow Creek. Common on the ridge between Hot Springs 
 and Corral Creek. 
 
 Chalcocite (copper glance, sulphuret of copper). In copper 
 veins in the Park Range. Bancroft Library 
 
 Chalcopyrite (copper pyrites). Of general occurrence in 
 small quantities in the mines. 
 
TO Grand County Minerals. 
 
 Chrysoprase. Sparingly in geodes on upper Grand River. 
 
 Cuprite (red oxide of copper). In copper veins in the Park 
 Range. 
 
 Cyanite. Occurs in the quartzite of Medicine Bow Peak. 
 Epidote. Massive and crystallized in the granitic rocks. 
 
 Galenite. Abundant in many of the mines. Massive veins 
 near the head of Troublesome Creek. 
 
 Heliotrope (bloodstone). Fine specimens occasionally met 
 with in the vein of green jasper on the hill at the junction of 
 Willow Creek and Grand River. 
 
 Hornblende. Of general occurrence in the archaean rocks. 
 
 Hypersthene. A constituent of the feldspar basalt from 
 Grand River, above Hot Springs. 
 
 Jasper. Veins of green, red and yellow jasper on the hill 
 at the junction of Willow Creek and Grand River. Ribbon 
 jasper is quite, common at this locality. Red and yellow jas- 
 per is more or less abundant on the ridges along Willow 
 Creek, in the vicinity of Hot Springs, and in the streams. 
 
 Lepidomelane (iron potash mica). A constituent of some of 
 the granite. 
 
 Magnetite (magnetic iron). An accessory mineral of much 
 of the granite. 
 
 Malachite (green carbonate of copper). Occurs as a stain 
 or incrustation at the surface of many of the copper veins in 
 the Park Range. 
 
 Moss Agate. Quite abundant on the south side of Williams 
 River, three or four miles from the Grand. 
 
 Mottled Agate. On Williams River; in the vicinity of 
 Hot Springs ; Willow Creek, and numerous other localities. 
 
 Muscovite (common mica). Common in archsean rocks > 
 frequently occurring in large masses. 
 
 Native Bismuth. Occurs in small particles in bismutite at 
 Cummuns City. The find is not satisfactorily verified. 
 
 Native Gold. In the alluvium of Willow Creek. 
 
 Native Silver. In leaf and wire form in some of the silver- 
 bearing veins. 
 
 Oligoclase (aventurine feldspar). A constituent of much of 
 the archsean rocks. 
 
 Onyx. Sparingly with chalcedony on the ridge south of 
 of Willow Creek. 
 
Jefferson County Minerals, ri 
 
 Orthoclase (common feldspar). The most abundant con- 
 stituent of the archsean rocks. 
 
 Plasma. Occurs in geodes found on upper Grand River. 
 
 Pyrargyrite (dark ruby silver ore). In small quantities in 
 the lodes of Campbell district. 
 
 Pyrile (iron pyrites). More or less abundant in the min- f 
 eral veins. 
 
 Pyroxene. Next to the feldspars, pyroxene is the most 
 universal constituent of the igneous rocks. 
 
 Quartz. Common, in crystal, small masses and a constitu- 
 ent of metamorphic and sedimentary rocks. 
 
 Sardonyx. Fine specimens occasionally met with on the 
 ridge south of Willow Creek, a mile or two from the Grand. 
 
 Stibnite (antimony glance). Float masses of stibnite and 
 quartz, two feet in thickness, are found between the head of 
 Troublesome Creek and Lost Lake. 
 
 Sphalerite (zinc blende). Abundant in many of the lodes. 
 
 Tetrahedrite (gray copper). Not unfrequently found in 
 the mines at Lulu. 
 
 JEFFERSON COUNTY MINERALS. 
 
 Actinolite. Columnar masses of green color near Bergen 
 ranch on Bear Creek, and at the entrance of Coal Creek canon. 
 
 Agate. Mottled agate common on Green Mountain. 
 
 Agatized Wood. Abundant on Table Mountains. 
 
 Alabaster. Massive white and mottled alabaster in Jurassic 
 shales near Morrison. 
 
 Albite (soda feldspar). A constituent of some of the arch- 
 sean rocks. 
 
 Allophanc. Forms a thin bluish crust on limonite in veins 
 near Bergen ranch, Bergen Park. 
 
 Amazonstonc. On Elk Creek and near the mouth of Tar- 
 ryall Creek, with smoky quartz and gothite. 
 
 Analdte. Pure white or transparent crystals in the basalt 
 of North Table Mountain, associated with other zeolite min- 
 erals. Specially abundant on the east side of the mountain. 
 Small crystals abundant on South Table Mountain. 
 
12 Jefferson Coimty Minerals. 
 
 Apophyllite. Well developed crystals of prismatic habit on 
 North Table Mountain. The larger crystals are usually ter- 
 minated by a number of small pyramids. 
 
 Aquamarine. Small inferior specimens on Tiffany ranch, 
 Bear Creek. 
 
 Aragonite. Occurs in a vein at Golden Gate. 
 
 Asphaltum (bitumen, mineral pitch). Forms crusts on 
 sandstone near Morrison. 
 
 Attgite. An essential constitiient of the augite-andesite 
 rocks of Green and Table Mountains. 
 
 Azurite (blue carbonate of copper.) Occurs as an incrus- 
 tation and minute crystals in the copper veins, Bear Creek. 
 
 Beryl. Abundant on Bear Creek and in Bergen Park. 
 Crystals vary in size from small ones to those two feet in di- 
 ameter. Translucent and good color specimens rare. 
 
 Biotite (black mica). A constituent of much of the gran- 
 ite and dike rocks. 
 
 Bismutite (carbonate of bismuth). In the Bismuth Queen 
 vein on Guy Hill. 
 
 Bismuthinite (sulphuret of bismuth). Associated with bis- 
 mutite in the Bismuth Queen lode, Guy Hill. 
 
 Bole (iron clay). Occurs as a dark brown clay on South 
 Table Mountain. 
 
 Brown Coal (lignite). Extensive veins at Golden, on Ral- 
 ston Creek, and other localities. 
 
 Calcite (carbonate of lime). Large masses of cleaveable 
 white calcite on Bear Creek. 
 
 Cairngorm (smoky quartz.) On Elk Creek and near the 
 mouth of Tarryall Creek, with amazonstone and gothite. 
 
 Carnelian. Small pieces of red and yellow carnelian on 
 Green Mountain. 
 
 Chabasite. Abundant in small crystals in the basalt of 
 North Table Mountain. 
 
 Chalcedony. Sparingly on Green Mountain and vicinity. 
 
 Chalcedony x. Sparingly between the mountains and Den- 
 ver. 
 
 Chalcocite (copper glance, sulphuret of copper). In copper 
 lodes on Bear Creek, in Bergen Park, and near Golden. 
 
 Chalcopyrite (copper pyrites). In the mineral veins on 
 Bear Creek and in Bergen Park. 
 
fefferson County Minerals. /j 
 
 Chlorophane (green fluor spar). Abundant in many veins 
 on Bear Creek. 
 
 Chrysocolla (silicate, of copper). Sparingly in the copper 
 veins on Bear Creek and in Bergen Park. 
 
 Cohimbite. In small masses 011 Turkey Creek. Analysis 
 shows the mineral to contain a small amount of tin and n 
 per cent of manganese. 
 
 Cuprite (red oxide of copper). In copper veins in Bergen 
 Park and on Bear Creek. 
 
 Enstatite. An accessory mineral of a -dike of diabase at 
 Morrison. 
 
 Epidote. Massive and crystallized in the granitic rocks. 
 Quite pretty crystals are found on Bear Creek. 
 
 Fluorite (fluor spar). Massive, purple, green and white, 
 in veins on Bear Creek. Purple near the mouth of Tarry all. 
 Massive on Cub Creek. 
 
 Galenite. Abundant in many of the veins on Bear Creek. 
 
 Garnet. Iron garnets are quite common in Bergen Park. 
 
 Gothite. On Elk Creek and near the mouth of Tarry all 
 Creek, with amazonstone and smoky quartz. 
 
 Gypsum. Abundant in Jurassic shale near Morrison. 
 
 Hematite. An earthy red hematite at Morrison. 
 
 Henlandite. Small colorless tabular crystals in the augite- 
 andesite of Green Mountain. 
 
 Hornblende. Of general occurrence in the archsean rocks. 
 
 Iceland Spar. Small yellowish masses in the amygdaloid 
 of the Table Mountains. 
 
 Jasper. Red and yellow jasper in the Green Mountain 
 region. 
 
 Kaolinite (porcelain clay). Extensive beds at Golden. 
 
 Laumontite. Occurs as a reddish-yellow sand-like material 
 and in compact masses in the basalt of North Table Mt. 
 
 Lepidomelane (iron potash mica). A constituent of some of 
 the granite. 
 
 Levynite. Of rare occurrence in small white and colorless 
 crystals associated with other zeolites on North Table Mt. 
 
 Limonite. Small masses in the veins of Bergen Park. 
 
 Magnetite (magnetic iron). An accessory mineral of much 
 of the granite. Loose crystals in the soil on Bear Creek and 
 in Bergen Park. 
 
14 Jefferson onnty. Miner alsi ..-.:. 
 
 Malachite (green carbonate of copper). Occurs as a stain 
 or incrustation at the surface of many of the copper veins in 
 Bergen Park and on Bear Creek. 
 
 Mesolite. Occurs as exceedingly delicate needles in the 
 basalt of North Table Mountain. 
 
 Microcline. Near the mouth of Tarryall Creek, with ama- 
 zonstone, smoky quartz, gothite and fluorite. 
 
 Mineral Resin. Small specimens of an undetermined va- 
 riety of resin in the soil on South Table Mountain and in the 
 coal veins. 
 
 Molybdenite. Occurs as an associate of bismuth minerals 
 on Guy Hill. 
 
 Muscovite, (common mica). Common in archaean rocks, 
 Large deposits on Deer Creek, where some mica mining has 
 been done. 
 
 Native Alum. In Jurassic shale on Bear Creek near Mor- 
 rison, and between Morrison and Platte Canon. 
 
 Native Copper. In considerable quantities in copper lodes 
 near Golden. Small specimens in the lodes on Bear Creek 
 and in Bergen Park. 
 
 Native Gold. In the alluvium of Clear Creek. 
 
 Native Sulphur. In small crystals. Exact locality not 
 known. 
 
 Natron (carbonate of soda). As crusts and in solution in 
 the waters of the lakes between Turkey and Bear Creeks. 
 
 Natrolite.- Occurs as delicate prisms sparingly deposited 
 on analcite or associated with that mineral in the basalt of 
 South Table Mountain. Less frequently on North Table Mt. 
 
 Oligoclase (aventurine feldspar). A constituent of much of 
 the archaean rocks. 
 
 Orthoclase (common feldspar). The most abundant con- 
 stituent of the archaean rocks. 
 
 Petroleum. Oozes from Cretaceous sandstone at Morrison. 
 
 Plagioclase. An essential constituent of diabase from Mor- 
 rison, in which it occurs in narrow prisms. 
 
 Ptilolite (new). A new zeolite described by Whitman Cross. 
 Occurs in small white tufts in the augite-andesite of Green 
 Mountain. Sparingly with other zeolites on the Table Mts. 
 
 Pyrite (iron pyrites). Small quantities in the veins of 
 Bergen Park and on Bear Creek. 
 
Jefferson County Minerals. 75 
 
 Pyroxene. An essential constituent of diabase from a dike 
 near Morrison. 
 
 Quartz. Large veins and masses of white quartz in Bergen 
 Park, on Bear Creek, and in the Guy Hill region. 
 
 Rock Crystal. Colorless quartz in crystals abundant on 
 the divide between Deer and Elk Creeks. 
 
 Rose Quarts. In large masses in Bergen Park. 
 
 Satin Spar (var. gypsum). Abundant in Jurassic shales 
 near Morrison. 
 
 Scolecite. Occurs sparingly in spheres with a radiate struct- 
 ure in the basalt of North Table Mountain. 
 
 Selenite (gypsum). In Jurassic shale near Morrison. 
 
 Silicified Wood. On South Table Mountain. Silicified 
 palm wood abundant between Golden and Denver. 
 
 Stilbite. Sparingly in small clear crystals with other zeo- 
 lites on North Table Mountain. 
 
 Thenardite (sulphate of soda). Occurs in quantity at Burd- 
 sall's lake near Morrison. 
 
 Thomsonite. In the basalt of North Table Mountain in 
 minute rectangular blades which are placed like a closed fan, 
 and in spherical concretions having a radiate structure. 
 
 Tourmaline. Fine black crystals in quartz on Bear Creek. 
 Near the head of Ralston Creek. 
 
 Jefferson County is also accredited with the following min- 
 erals, btit their occurrence needs verification : 
 Aluminite, Mt. Vernon. 
 Antrimolite, Table Mountains. 
 Egeran, Gennessee ranch on Bear Creek. 
 Idocrase, Bear Creek. 
 Pyrrhotite. 
 
 Wavellite, Table Mountains. 
 Wheelerite, in the coal. 
 Topazolite, Malachite lode, Bear Creek.