/ 



12 ME.TALS. 



2. GOLD. 



Gold occurs mostly native, being either pure or alloyed 

 with silver and other metals. It is occasially found miner- 

 alized by tellurium. 



NATIVE GOLD. 



Monometric. In cubes, without cleavage. Also in grains, 

 thin laminae and masses ; sometimes filiform or reticulated. 



Color various shades of gold-yellow ; occasionally nearly 

 silver- white, from the silver present. Very ductile and mal- 

 leable. H = 2*5 — 3. Gr=12 — 20, varying according to 

 the metals alloyed with the gold. 



Composition, Native gold usually contains silver, and in 

 very various proportions. ^ The finest native gold from Rus- 

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

 Gr= 19-099. A gold from Marmato afforded only 73*45 

 per cent, of gold, with 26*48 percent, of silver ; Gr=12-666. 

 This last is in the proportion of 3 of gold to 1 of silver. The 

 following proportions also have been observed : 3^ to 1 ; 5 

 to 1 ; 6 to 1 ; 8 to 1, and this is the most common ; 12 to 1, 

 also of frequent occurrence. y 



r Copper is often found in alloy with goldAand also palla- 

 dium and rhodium. A rhodium-gold fromjVLexico gave the 

 specific gravity 15*5 — 16*8, and contained 34 to 43 per cent, 

 of rhodium. 



Dif, Iron and copper pyrites are often mistaken for gold 

 by those inexperienced in ores. Gold is at once distinguished 

 by being easily cut in slices and flattening under a hammer. 

 The pyrites when pounded are reduced to powder ; iron 

 pyrites is too hard to yield at all to a knife, and copper pyr- 

 ites affords a dull greenish ppwder. Moreover, the pyrites 

 give off sulphur when strongly heated, while gold melts with- 

 out any such odor. 



Obs. Native gold is mostly confined to those suDcrys- 

 alline slaty or schistose rocks that abound in quartz veins, 

 and mofe especially to talcose and chloritic slates. It occurs 



In what condition does gold occur in nature ? What is the crystal- 

 lization of native gold 1 What are its common forms in the rocks 1 

 Mention its characters. With what is it alloyed 1 How is gold dis- 

 tinguished from iron and copper pyrites? From what rocks is gold o 

 ained 1 



