110 



DESCRIPTIONS OF MINERALS. 



Composition. Native gold usually contains silver, and in 

 very various proportions ; and the color becomes paler with 

 the increase of silver. The finest native gold from Eussia 



2. 



yielded gold 98-96, silver 0*16, copper 0*35, iron 0*05 ; 

 G. =19-099. A gold from Marmato afforded only 73-45 per 

 cent, of gold, with 26-18 per cent, of silver; G. = 12*666. 

 This last is in the proportion of 3 of gold to 2 of silver. The 

 following proportions also have been observed : 3 J to 2 ; 5 

 to 2 ; 3 to 1 ; 4 to 1, and this the most common ; 6 to 1 is 

 also of frequent occurrence. Average of California native 

 gold is 88 per cent, gold, and the range mostly between 87 

 and 89; the range of the Canadian, mostly between 85 and 

 90 ; of Australian, between 90 and 96 per cent., and the 

 average 93 J. The Chilian gold afforded Dome)ko 84 to 96 

 per cent, of gold, and 15 to 3 per cent, of silver. The more 

 argentiferous gold has been called Electrum; the atomic pro- 

 portion of 1 : 1 between the gold and silver corresponds to 

 35-5 per cent, of silver, and that of 2 : 1, to 21 '6 per cent. 



Copper is occasionally found in alloy with gold, and some- 

 times also iron, bismuth, palladium and rhodium. A rliodium- 

 gold from Mexico gave the specific gravity 15"5-16-8, and 

 contained 34 to 43 per cent, of rhodium. A bismuth gold 

 has been called Maldonite. 



Dijf. Iron and copper pyrites are often mistaken for gold 

 by those inexperienced in ores ; but these are brittle minerals, 

 while gold may be cut in slices, and flattens under a hammer. 

 Pyrite is too hard to yield at all to a knife, and copper 

 pyrites affords a dull "greenish powder. Moreover pyrite 

 gives off sulphur when strongly heated, while gold melts 

 without, odor. 



