GOLD. 55 



when protochloride of tin is added to the solution ; or a dark 

 brown powder (really pure gold) will be precipitated when a 

 solution of sulphate of iron (copperas) is added. 



Gold, nearly invariably in a native state, is very widely 

 distributed over the globe, and is obtained from the gravel, 

 sand, clay, "drift beds," washed down from gold-bearing 

 strata (sometimes the rich part of the deposits has brown 

 ferruginous matter associated with it), or else from quartz 

 lodes traversing the older slaty and metamorphic rocks and 

 less abundantly in granite. It is also found scattered about 

 in rocks of a granular nature.* The ordinary gold-bearing 

 lodes and deposits occur as represented in Fig. 37, which 

 represents the structure of the Ural Mountains. Iron pyrites, 

 copper pyrites, magnetic iron, blende, galena, &c., are some 

 of the metallic minerals often very commonly associated 

 with gold in a lode, the iron pyrites in veins of a gold- 

 bearing district nearly, if not always, containing a certain 

 amount of the precious metal. On the surface of a lode 

 the gold specks may perchance be noticed, by the eye or 

 lens, in the cavities of the brown Honeycombed quartz rock, 

 although free gold may be invisible in the pyrites rock 

 deeper in the lode and unexposed to atmospheric and other 

 changes affecting the surface portions. 



Taking for granted that gold is found under the usual 

 circumstances heretofore mentioned, one must remember it 

 has been payably obtained in unexpected ways : for example, 

 in sinter, in trachyte, in very peculiar conglomerates, &c. 

 Usually the discovery of alluvial gold leads to that of lodes 

 in the neighbourhood ; but oecause gold deposits are not 

 found, it does not follow that the country is non-auriferous. 

 So, too, because gold is not noticed in the outcrop of a lode, 

 it does not follow that the lode is necessarily an unprofit- 

 able one. 



It would be out of place here to discuss the theory of how 

 gold in veins was originally formed. In alluvial deposits 

 the grains are usually worn into shape, and so in some other 

 deposits. But it may be remarked that in certain con- 

 glomerates the gold is found in thin plates, a fact which 

 suggests that the law of gravity does not apply to the dis- 

 * Such as granite, diorite, gabbro, &o. 



