144 EEPOET UNITED STATES GEOLOGICAL SURVEY. 



GosLARiTE.— On the dumps of the Wood lode, Leavenworth Gulch, 

 near Central. 



Graphic granite. — See Pegmatite. 



Graphite. — Trinidad Mine, Las Animas County. Brad lode, San Juan 

 district. 



Greenockite. — On sphalerite of the Dallas Mine, Black Hawk, Run- 

 ning Lode, Quartz Hill, Nevada. In mine of galena, on South Boulder. 



Gypsum. — Occurs at numerous localities. 



Gypsum. — Compact in the Triassic and Cretaceous, sometimes Car- 

 boniferous formations. 



Selenite. — Good crystals are rare. This form is more frequently 

 found than the compact. Occurs in the Upper Carboniferous beds of 

 Western and the Tertiary beds of Southern Colorado. In the Juras- 

 sic formation along the Front Range. On Eagle River, along the 

 Lower White and Grand. Table Mountain, Golden. 

 Alabaster. — Occurs at Mount Vernon. 



Halite. — Salt-works of South Park, along some parts of the Platte 

 River, in springs. Found at salt-licks in various parts of the Terri- 

 tory. Canon City, Siubad's Valley, Greenhorn Mountains. 



Hematite. — 



Specular. — Rhombs on quartz crystals. Topaz Buttes ; Procer Hill, 

 near Central ; Phillip's Mine, Silver Hills ; in the mines of Elk Mount- 

 ain district, Bear Creek, Jefferson County, TJnaweep Canon. Fine 

 crystals, iridescent, Safi Juan. 



Micaceous. — Caribou, Ralston Creek, Unaweep Canon, Sopris Peak, 

 single crystals on quartz and some inclosed in amethyst at the Lit- 

 tle Giant mines, near Silverton. 

 Fibrous. — Phillips Mine, Silver Hills. 



Henryite. — Found first at the Red Cloud and Cold Spring mines ; later 

 in all the telluride mines of Gold Hill, Ward, Sugar Loaf, and Sun- 

 shine districts. . Fine crystals are very rare ; minute ones are found, 

 but rather imperfect. An analysis* furnished the following result : 



Pb 53.19 



Fe 5.05 



Ag 0.31 



All trace. 



Te 41.45 



Specific gravity 8. 5253 



(Compare altaite.) 

 Hessite. — Gold Hill, Boulder County ; a telluride that may be hessite 

 has been found in the Hodgkiss lode, on the divide between Uncom- 

 pahgre and Animas Rivers. A similar one is reported from the vicin- 

 ity of Parrott City, on the La Plata. Prof. B. Silliman examined a 

 specimen from the Red Cloud Mine,t and found : Au, 7.131 per cent. ; 

 Ag., 51.061 per cent. A specimen of hessite from the Red Cloud 

 Mine, analyzed by Genth,| showed the following composition: 



Per cent. 



Gold 0.22 



Silver 59.91 



Copper 0.17 



Lead 0.45 



Zinc trace. 



Iron 1.35 



Tellurium 37.86 



' * Eep. U. S. Geol. Surv., 1873, p. 353. ~~ 



t Rep. U. S. Geol. Surv., 1873, p. 689. 

 t Proc. Am. Phil. Soc, Phila., vol. xiv., p. 227, 1876. 



