62 SILVER-LEAD DEPOSITS OF EUREKA, NEVADA. 



occurs in the form of blende (sulphide), calamine" (silicate), and prob- 

 ably as smithsonite (carbonate). It is most common in the form of cala- 

 mine. Manganese occurs mostly as wad. Arsenic is almost entirely com- 

 bined with lead as arsenic acid, and the same is most likely the case with 

 the small percentage of antimony which the ore contains. 



In the above analysis it will be seen that the sulphur has been esti- 

 mated almost entirely as sulphuric acid, although it is partly combined with 

 lead in the form of galena. Most of the sulphuric acid is combined with 

 lead, though to some extent it is no doubt combined with calcium. Silica 

 is present in the form of quartz principally and combined with iron and 

 aluminium. The calcium and magnesium are present, combined for the most 

 part with carbonic acid. 



The silver is found in the form of chloride and sulphide, and the gold 

 exists in all probability in a finely divided metallic state. In this analysis 

 no account has been taken of the chlorine, and for some unaccountable 

 reason molybdic acid has been omitted. It must have been present in the 

 ore analyzed, as wulfenite is a common mineral in the Ruby Hill ores. The 

 footing of the different elements in this analysis amounts to 100.52, but it 

 would be considerably less if a portion of the sulphuric acid had been esti- 

 mated as sulphur, which would leave room for several substances which are 

 unquestionably present. 



In a qualitative analysis of the Ruby Hill ores, Dr. Melville, of the 

 United States Geological Survey, detected the following elements: 



Relative value of the ores of Prospect Mountain and Ruby Hill. The Ol'eS of PrOSDeCt Moun- 

 tain are very similar to those of Ruby Hill, though perhaps there is a greater 



"In this report the word calamine will ho used to designate the silicate of zinc, and smithsonite 

 for carhonate of zinc, this being the nomenclature adopted by Dana. These terms have been used by 

 various writers in a promiscuous manner, some nsing smithsonite to designate the silicate, and calamine 

 the carbonate. Brogniart used calamine for silicate and smithsouite for carbonate. Brooks and Miller 

 in 18M2 reversed these names. Qneustedt. called the carbouate calamine and the silicate willemite. 



