GOLD AND SILVER. 447 



hepatic ore. Cinnabar is easily volatilized, and possesses high specific 

 gravity. The Californian mines are very rich. Spain also produces a large 

 quantity. It is opaque, and carmine in colour. 



SILVER occurs native, or in ores. The latter are as follows : The 

 sulphide, or the vitreous silver (argentite) ; antimonial silver ; and the com- 

 bined sulphides, of antimony and silver. There are many silver minerals, 

 such as the chloride (horn silver, or kerargyrite), bromide, and carbonate of 

 silver, bismuthic silver, etc. The bromide and iodide are bromargyrite and 

 iodargyrite. Silver occurs most frequently associated with gold ; natural 

 alloys of these two metals are found, containing from O'i6 to 38*7 per 

 cent, of silver, which causes considerable variations both of colour and 

 density. In addition to this alloy, we may mention sylvanite (graphic tel- 

 lurium), which contains, besides gold and silver, one of the rarer metals viz., 

 tellurium. 



Fig. 474. Gold crystals. 



GOLD is our most precious mineral, and is generally found native. It 

 exists in sand and in certain rocks. It crystallizes in various forms, and in 

 Mexico it is found in companionship with silver and copper sulphides. 

 Australia and California render the most valuable supplies of the metal. 



PLATINUM is also found native, and rarely is crystals. It is often 

 alloyed with other metals, chiefly with iron or gold ; also with diamonds. We 

 have already considered it as a metal. Little remains to be said about salts and 

 resins, for with the exception of those we have referred to under Chemistry, 

 they are of little value. The bitumens, rock oil, etc., which exude from the 

 earth, are very useful, and as asphalt and petroleum play an important part 

 in the civilized world, but scarcely come under the strict rule of minerals 

 as we consider them, and with this reference we close our sketch of 

 Mineralogy. 



