386 GEOLOGY OF THE COMSTOCK LODE. 



leached out of the diabase is comparable with tliat which the Lode must 

 have contained at its discovery. There are also relations between the 

 inclosing- rocks and the ore deposits not found in contact with diabase. 



The gangue of the Comstock is almost exclusively quartz, though cal- 

 cite also occurs in limited areas. The ore minerals elude investigation for 

 the most part because they are so finely disseminated as merely to stain 

 the quartz, but it is fairly certain that they are principally argentite, and 

 native silver and gold, accompanied in some cases by sulph-antimonides, 

 etc. The chloride has rarely been identified. Where ore is found in dio- 

 rite, or in contact with it, it is usually of low grade, and its value is chiefly 

 in gold. The notably productive ore bodies have been found in contact 

 with diabase, and they have yielded by weight about twenty times as much 

 silver as gold. 



Reagents. — It would pcrhaps be legitimate to infer from the chemical 

 phenomena enumerated and the association of minerals that waters charged 

 with carbonic acid and h}-drogen sulphide had played a considerable part 

 on the Comstock. This is not, however, a mere inference, for an advance 

 boring on the 3,000-foot level of the Yellow Jacket struck a powerful stream 

 of water at 3,080 feet (in the west country), which was heavilv charged with 

 h3-drogen sulphide and had a temperature of 1 70° F , and there is equal 

 evidence of the presence of carbonic acid in the water of the lower levels. 

 A spring on the 2,700-foot level of the Yello/r Jacket, which showed a tem- 

 perature of above l."" 0° F., Avas found to be depositing a sinter largely com- 

 posed of carbonates. 



Baron v. Richthofen was of opinion that fluorine and chlorine had 

 played a large part in the ore deposition on the Comstock, and that this 

 is possible cannot be denied; but, on the other hand, it is plain that most 

 of the phenomena are sufficiently accounted for on the supposition that tiie 

 agents have been merely solutions of carbonic and hydrosulphuric acids. 

 These reagents will attack the bisilicates and feldspars. The result would 

 be carbonates and sulphides of metals, earths and alkalies, and free quartz; 

 but quartz and the sulphides of the metals are soluble in solutions of car- 

 bonates and sulphides of the earths and alkalies, and the essential constitu- 

 ents of the ore might, therefore, readily be conveyed to openings in the 



