1114 A TREATISE ON METAMORPH1SM. 



tions at temperatures of 100° or somewhat higher, has actually succeeded 

 in producing artificially the following sulphide minerals: Pyrite, chalcopy- 

 rite, bornite, chalcocite, covellite, galena, bournonite, miargyrite, jamesonite, 

 and pyrrhotite." 



Doubtless in many instances the precipitation of the oxidized salts is 

 accomplished by an alkaline sulphide instead of by hydrogen sulphide. 

 It has already been pointed out that the action of alkaline carbonates upon 

 salts such as iron sulphide produces alkaline sulphides. For instance, 

 sodium carbonate reacts upon iron sulphide, producing- -sodium sulphide. 

 Where this sulphide comes into contact with any of the oxidized salts, or 

 other soluble sulphates, the metals may be thrown down as sulphides. 



A particularly good case of precipitation due to mingling of solutions 

 is that of the lead and zinc deposits of the Missouri-Kansas district, described 

 by Bain, 6 where waters rise through the Carboniferous limestone and come 

 into contact with precipitating solutions derived from it. It is uncertain 

 whether the precipitating solutions are alkaline sulphides, hydrogen sul- 

 phide, or reducing agents derived from organic matter, but probably 

 hydrogen sulphide produced by reactions upon base sulphides is the more 

 important precipitating agent. 



Of the greatest importance in the precipitation of sulphides from 

 ascending waters, the metals of which have been transported in the form of 

 oxidized salts, is the reaction upon the solutions of previously precipitated 

 sulphides. The sulphides of the less valuable but more abundant metals 

 are important agents in the precipitation of the sulphides of the more valu- 

 able metals from the solutions of their oxidized salts. That such precipitation 

 occurs was shown by Anthon in 1837? In 1888 the same subject was inves- 

 tigated by Schiirmann, whose results are but slightly different from those of 

 Anthon. Schurmann d gives the following series of metals, the order being 

 increasing strength of affinity for sulphur: Manganese, thallium, arsenic, 

 iron, cobalt, nickel, zinc, lead, tin, antimony, cadmium, bismuth, copper, 

 silver, mercury, palladium. He shows that the sulphide of the first mem- 



«Tschermaks Min. u. Petrog. Mitth. vol. 7, 1886, p. 535 et seq. 



b Bain, H. F., Van Hise, C. R., and Adams, G. I., Preliminary report on the lead and zinc deposits 

 of the Ozark region: Twenty-second Ann. Kept. U. S. Geol. Survey, pt. 2, 1901, pp. 212-214. 



c Anthon, E. F., Ueber die Anwendung der auf nassem wege dargestellten Schwefelmetalle bei der 

 chemischen Analyse: Journ. f. Prak. Chemie, 1st series, vol. 10, 1837, p. 353. 



''Schiirmann, Liebig's Annalen der Chemie, vol. 249, 1888, p. 342. 



