GEOLOGICAL SURVEY OF THE TERRITORIES. 203 



iferoLis galena, brittle silver ore, fahlerz, specular iron, hematite and 

 magnetic pyrites, cernssite and anglesite, native gold and silver, horn 

 silver, embolite, (confined cliiefly to the neighborhoods of Georgetown 

 and Snake Eiver, 1 believe, as far as yet ascertained,) titanic iron ore, 

 micaceous iron ore, spathic iron ore, Smithsonite, cojjper glance, coal 

 and Albertine coal. These comprise the principal ores which I have 

 observcJ, but time and more thorough search will undoubtedly disclose 

 to the mineralogist, if not to the metallurgist and miner, many as yet 

 hidden treasures. 



Gilpin County and the region about Empire are rated as gold fields, 

 and the values of ores from these and some other districts are given in 

 ounces of gold per ton; whereas the adjacent country around George- 

 town, abounding as it does in argentiferous galena and silver glance, 

 (called simply "snlphuret,") has the number of ounces silver per ton as 

 its standard. In some few veins, as the Whale Lode near Idaho City, 

 the values of the gold and silver present in the ore are nearly equal. 



A more detailed specification of the ores follows: 



Iron pyrites^ (FeSa.) — Almost universal in the mines. Occurs in 

 cubes from the size of a pin's head to those of an inch on the sides. Also 

 in pentagonal dodecahedra. 



Copper pyrites^ (CuaS+FeS^.) — Is only second to iron pyrites in the 

 frequency of its occurrence.* 



Zincblen.fle^ (ZiiS.) — Is also very common, especially in the Georgetown 

 region. Fine specimens Avere obtained from the Baker Lode, West Ar- 

 gentine and the Grifiith Lode, close by Georgetown. Also from Gilbert's 

 (Ibrraerly Common wealth Mining Company) Lode, near Nevada City. 



Galena^ (PbS.) — Usually argentiferous. In all the lodes in the vicin- 

 ity of Georgetown. Contains from one hundred to six hundred ounces 

 silver per ton.t 



Brittle silver ore^ (Stephauite .5AgS+Sb2S3.) — Occurs in the silver mines 

 of Georgetown. (Terrible and Brown lodes.) 



Fahlerz, [(4RS-f ^CugS) QS3.E=Fe, Cu, Zn and often some Ag and 

 Hg= Q=Sb and As. J — Also in the region around Georgetown. The 

 formulai liere given are from Naumann's Mineralogy. I am not aware 

 that Hghas been discovered in this ore, but as it coincides in its phys- 

 ical i)roperties with the ordinary fahlerz, I ax)pend the above formula. 



Light ritby silver, [Proustite,) (SAgS.AsSg); Bark ruby silver, {Py- 

 rargyrite,) (3AgS. SbSo.) — Handsome specimens of these two ores were 

 observed intermixed with the galena from the Brown Lode. Also from 

 Snake Eiver. 



Silver glance, (AgS.) — From the Georgetown neighborhood. Equator 

 and Terrible lodes. A ton of galena, containing much of this ore, 

 was recently sold by a gentleman of Central City to Professor Hill for 

 $1,900 cash, and the latter realized a profit of $700 from it. 



^ Both iron and copper pyrites of this region contain gold in indefinitely line particles. 

 The former is, iu fact, the gold ore. Where these minerals have been exposed to the 

 action of the Aveather, they have been decomposed and the gold set free. The valne of 

 the gold ill a ton A^aries from nothing to five hundred dollars, and even more. I have 

 obserA^ed small oetahedra of gold on the crystal faces of iron pyrites from the Pleasant 

 View mine near Central City. 



t It is somewhat remarkable that these veins of galena generally " pinch np " or grow 

 snialler as the depth increases. I take this general statement from the best authority I 

 could obtain on the subject. A gentleman well acciuainted Avith the Georgetown ores 

 informed me that all attempts hitherto to produce lead for the market had failed from 

 deficiency in the supply of galena. This statement, which I give for Avhat it is worth, 

 appears all the more remarkable when one compares it Avith the experience of miners in 

 Freiberg, Przibram, and Clausthal. 



