142 REPORT UNITED STATES GEOLOGICAL SURVEY. 



A total average prepared from thirty-four analyses of Colorado bitu- 

 minous coal will furnish an idea as to its position in mineralogical classi- 

 fication. 



Water 6.436 



Fixed carbons 5'2, 617 



Volatile combustible matter 1 34. 096 



Ash 6.835 



Specific gravity 1. 325 



CoLORADOiTE. — Occurs in Boulder County, in the Keystone Mine; in 

 the Smuggler Mine, Ballerat district, Professor Genth furnishes sev- 

 eral analyses.* 1, Keystone Mine ; 2 and 3, Smuggler Mine. 



(1) (2) (3) 



Per cent. Per cent. Per cent. 



Hg 52.28 Quartz 2.90 3.05 



Te = 42.95 Au 3.46 7.67 



AloOgFe^Os 2.44 Ag 2.42 7.18 



V2O3 0.70 Hg... 55.80 48.74 



Mg 0.11 Cu trace. 0.16 



CaO 0.84 Zq trace. 0.50 



Fe 1.35 0.92 



99.32 Te 36.24 34.49 



99. 27 99. 66 



CoLUMBTTE. — Found occurring in prismatic needles piercing the Zir- 

 kon of Pike's Peak. . 



Copper. — Native; arborescent in the Gregory lode. "Ward district, 

 Boulder County ; Bergen's ranch. Arborescent on Jones's Moun- 

 tain ; in almond-shaped nuggets in placiers of Eio San Miguel. 



COPPERASITE. — See Jarosite. 



CovELLiTE.— Mosquito, Central City, Canon City. (Loew.) 



Cuprite. — In crystals, from Sacramento Gulch and from the Sweet 

 Home Mine, Malachite lode. Bear Creek, Gendhemas lode, Tucker's 

 Gulch ; massive on the Rio Dolores. 



Dolomite. — From the Four-Mile Creek. Occurs as rock in a number 

 of the formations of the State. Very rarely crystalized. Small geodes 

 in Middle Cretaceous shales are sometimes lined with dolorite crys- 

 tals. 



Dyscrasite. — Eeported from the head of the Uncompahgre. 



Embolite. — Peru district ; Snake River ; Gold Hill. 



Enargite. — Near Black Hawk. Found in the Powers Mine, Russell 

 district, Gilpin County. 



Epidote. — Crystals associated with garnet on Gunnell Hill, Central. 

 Throughout the metamorphics of the Front Range in minute crystals ; 

 crystals in the Sangre de Cristo Range ; a large number of the horn- 

 blendic dikes contain massive epidote together with quartz. On the 

 summit of Mount Bross ; LaKC Creek Canon ; Elk Mountain Range ; 

 on Trail Creek. 



Fahlerz. — Terrible, Colorado Central, Pelican, and other mines of 

 Georgetown ; No-Name, Caribou, aud others at Caribou ; Mount 

 Princeton. Argentiferous, mostly antimouial, sometimes arsenical in 

 the silver mines of the San Juan region. Crystals are very rare. 



Feldspar. — See Andesite, Labradorite, Oligoclase, Orthoclase, 

 and Sanidite. 



Fire clay. — Golden, Ralston, Boulder, &c. Good fireclay is obtained 

 from the Animas coal-bearing beds. 



Float-stone. — See Pumice. 



Flos Feeri. — See Aragonite. 



Fluorite. — Terrible mine, Georgetown, in light-green cubes; in small 

 crystals and massive, of violet color, on Mount McClellan and Gray's 



(*Z eitschr. fur Kryst. und Min. P. Groth, \ol. 11, No. 1, 1877.) 



