SOLUTION OF SULPHIDES. 1107 



At Sulphur Bank boric acid is also present." Hydrogen sulphide has also 

 been observed by Lindgren in the ascending waters of the Federal Loan 

 mine of the Sierra Nevada. He says that at the Federal Loan mine "an 

 unmistakable odor of sulphureted hydrogen was noted in the vicinity of 

 the spring." b 



Finally, Doelter has shown tnat the sulphides are soluble in pure 

 water, to some extent. He has thus dissolved measureable quantities of 

 pyrite, galena, stibnite, sphalerite, chalcopyrite, arsenopyrite, and bour- 

 nonite. c 



Since sodic carbonate, sodic sulphide, and hydrogen sulphide s,re prob- 

 ably so important in the transportation of the sulphides of the metals, it is 

 advisable to consider the possible sources of these compounds. This sub- 

 ject is of further importance, because it will be seen that hydrogen sulphide 

 is also an important precipitating agent. 



It has been fully explained in other places (pp. 176-177, 609-610, 

 677-679) that carbon dioxide is liberated on a great scale in the zone of 

 anamorphism, and that most of this carbon dioxide joins the deep circulation. 

 It has been seen also that the process of carboiiation of the silicates is 

 perhaps the most fundamental reaction of the zone of katamorphism — that 

 in which aqueous ore deposits occur. Of the elements which the silicates 

 contain, the most easily carbonated is sodium. It should follow that sodium 

 carbonate is an abundant salt in the ground water. This theoretical 

 conclusion is fully confirmed by observation. 



We shall now see that abundant sodium carbonate results in the for- 

 mation of the other compound most frequently present where sulphides of 

 the valuable metals are in solution. 



Stokes has shown recently that by the reaction of sodic carbonate 

 alone upon pyrite or marcasite sodic sulphide is produced. His reaction is 

 as follows: 



8FeS 2 +15Na 2 C0 3 =4Fe 2 3 +14Na 2 S+Na 2 S 2 3 +15C0 2 



«Le Conte, Joseph, and Rising, W. B., The phenomena of metalliferous vein formation now in 

 progress at Sulphur Bank, California: Am. Jour. Sci., 3d ser., vol. 24, 1882, pp. 23-33. Le Conte, 

 Joseph, On the mineral vein formation now in progress at Steamboat Springs, compared with the 

 same at Sulphur Bank: Am. Jour. Sci., 3d ser., vol. 25, 1883, pp. 424-428. 



6 Lindgren, Waldemar, The gold-quartz veins of Nevada City and Grass Valley districts, California: 

 Seventeenth Ann. Rept. U. S. Geol. Survey, pt. 2, 1896, pp. 12i-122. 



<• Doelter, cit, pp. 321-323. 



