1096 A TREATISE ON METAMORPHISM. 



and suggests that the original solution and deposition of native gold and 

 the sulphides are frequently connected; therefore it is reasonable to infer 

 that the conditions which produced sulphides may also have resulted in . 

 the precipitation of gold." 



Liversidge has shown experimentally that pyrite, galena, arsenopyrite, 

 and nearly all other sulphide minerals will precipitate gold completely from 

 solutions of auric chloride? The frequency with which gold occurs associ- 

 ated with or inclosed by pyrite suggests that this is a very important 

 reaction. This relation is well illustrated by the gold-quartz veins of the 

 Sierra Nevada described by Lindgren, where in the deeper parts of the lodes 

 beyond the belt of surface oxidation the pyrite and the gold are intimately 

 associated. Lindgren says that the intimate connection of the gold with 

 the sulphides was very likely caused by the tendency of gold solutions to 

 be precipitated by particles of sulphides." 



In certain cases gold occurs associated with both carbonaceous material 

 and the base sulphides. This is well illustrated by the argillite of the 

 gold-quartz veins of the Banner mine described by Lindgren/' and by the 

 Bendigo reefs of Australia." In such cases the question may arise as to 

 which of the two is the precipitating agent; but the more intimate 

 association of the gold with the pyrite suggests that the pyrite is the 

 precipitating agent for the gold (see PI. XI, A), and this agrees with the 

 experimental work of Liversidge, which shows that the metallic sulphides 

 precipitate gold from solutions more readily than organic matter/ 



Recently Lenher and Hall- have shown that the natural tellurides of 

 gold, silver, and mercury are capable of rapidly and completely precipitat- 

 ing metallic gold from its solutions. This they have accomplished with 

 calaverite (AuAgTe 2 ; Au 39.5, Ag 3.1, Te 57.4) (Au 41.76, Ag .80, Te 56.64, 



"Lindgren, cit. , p. 184. 



''Lindgren, Waldemar, Gold-quartz veins of Nevada City and Grass Valley: Seventeenth Ann. 

 Rept. U. S. Geo!. Survey, pt 2, 1896, p. 182. Liversidge, A., On the origin of gold nuggets: Proc. 

 Roy. Soc. New South Wales, vol., 27, 1893, p. 303. 



' c Lindgren, cit, p. 1S4, PI. VII, p. 138, and PI. VIII, p. 140. 



(I Lindgren, cit., PI. VIII, fig. c, p. 140, and p. 156. 



'■ Rickard, T. A., Origin of gold-bearing quartz of Bendigo reefs, Australia: Trans. Am. Inst. 

 Min. Eng., vol. 22, 1894, pp. 314-317. 



/Liversidge, A., On the origin of moss gold: Proc. Roy. Soc. New South AVales, vol. 27, 1893, 

 p. 287. 



<J Lenher, Victor, Naturally occurring telluride of gold: Jour. Am. Chem. Soc, vol. 24, 1902, pp. 

 355-360. Lenher, Victor, and Hall, R. D., Action of tellurium and selenium on gold and silver salts: 

 Ibid., pp. 918-927. 



