ORES OF LEADYILLE MINES. 617 



Higliland Chief. — Sand. Masses of indistinct crystals of cerussite, not cemented. 



Homestalie. — Hard. Masses of galena and pyrites in small crystals, cemented with 

 dolomite and siderite. 



Hibernia. — Sand. Soft clay, with indistinct cerargyrite, but no cerussite. 



Iron. — Hard. Crystalline masses of distinct and indistinct crystals of cerussite, 

 cemented witlj oxide of iron; part of the carbonate of lead colorless, part with a 

 blackish tinge (in examining the lanarkite of the Florence mine it was found that this 

 tinge is due to sulphuret of silver) ; also hard masses of pure galena in large crystals, 

 cemented by small ones; also masses of large and small distinct crystals of cerussite, 

 cemented by manganiferous oxide of irou ; also masses of hematite and occasionally 

 red and yellow ocher ; also nodules of cerussite, cemented with ocher. 



La Plata. — Sand. Bluish -black and yellow masses of small crystals of cerussite. 



Matchless. — Sand. Soft silicious masses impregnated with cerussite. 



Horning Star. — Hard. Hard carbonate. 



Eocl-. — Hard. Masses of crystalline cerussite, with yellow spots of ocher and 

 greenish spots of embolite; also most varieties previouslj' described. 



Robert E. Lee. — Sand. Chloride ore, ocherous yellow (a qualitative examination 

 of this ore showed that the ocher contains a considerable quantity of antimouiate of 

 iron); the silver exists in the state of embolite, containing a very small quantity of 

 iodide of silver. 



Virginius. — Hard. Uniform masses impregnated with cerussite. 



It must be noticed that the principal varieties described here are to be found in 

 most mines, although the bismuth ores are confined to the Florence mine, and those 

 free from lead, or dry ores, are found mainly in the Lee and Hibernia mines. A glance 

 at the assays of ores made at different smelters will give a correct idea of the relative 

 contents of the ores in lead and silver, and also in gangue and iron, so that these 

 assays have a mineralogical and geological signification, as well as a commercial one 



COMPOSITION OF ORES. 



A complete examination of the ores from every mine would have formed a 

 most interesting chapter, but the field of investigation opened in Leadville was so 

 vast that its accomplishment would have involved a far greater time than could 

 be given to this study, which has therefore been jierforce restricted to the most impor- 

 tant points. 



Carbonate ores — The interesting observation was made that when cerussite is tinged 

 with black this color is due to sulphuret of silver, so that to some extent the richness 

 of the ore in silver can be ascertained by the eye. The following exhaustive analyses 

 of the carbonate ore of two of the principal mines of Leadville were made by Dr. W. 

 F. Hillebrand in the laboratory of the Survey at Denver: 



Analysis I. — Adelaide ore. Sand in lumps, formed of masses of small crystals of 

 colorless cerussite, cemented by cerussite, clay, and oxide of iron. 



Analysis JJ.— Little Chief ore (sand in lumps). Formed of masses of distinct and 

 indistinct small crystals of cerussite with a bluish-black tinge, full of whitish and yel- 

 lowish spots and cavities. 



