46 MINERALOGY. 



most common ore of mercury, the sulphuret, was noticed 

 in 56. 



90. Silver. This metal is found pure, in alloy, and in 

 chemical combination with sulphur, arsenic, chlorine, va- 

 rious acids, etc. When it is found native it is not usu- 

 ally alone, but is alloyed with copper, and sometimes 

 with gold. The copper in the alloy sometimes amounts 

 to 10 per cent. The chief ores of silver, the sulphur ets, 

 were noticed in 53. 



91. Gold. This metal has no disposition to unite with 

 oxygen or with other elements, and therefore is found 

 in nature either pure, or alloyed with some other metals, 

 chiefly silver and copper. The only chemical compound 

 formed by gold in nature is with tellurium, termed a tel- 

 lurid of gold, and this is quite rare. As you have al- 

 ready learned, iron and copper pyrites have often been 

 supposed to be gold by those who are ignorant in regard 

 to minerals. But the distinction is easily made, for gold 

 flattens out on being hammered, and is readily cut, while 

 the pyrites break in pieces on being hammered, and nei- 

 ther of them can be cut in slices, no impression even be- 

 ing made by the knife on the iron pyrites. Besides, the 

 pyrites, on being exposed to a strong heat, emit a sul- 

 phureous odor, while the melting gold is odorless. Gold 

 is commonly found in grains or rounded masses of vari- 

 ous sizes, but sometimes it is crystallized in the form of 

 the cube or octahedron. Sometimes large lumps have 

 been found. The largest lump that has yet been ob- 

 tained was from California. It furnished 109 pounds 

 and 4 ounces of pure gold. Gold is diffused in most 

 countries in small quantities ; but there are some locali- 

 ties where it abounds, as the Urals, Hungary, Spain, va- 

 rious parts of South America and Africa, but especially 

 Australia and California. In these two last localities it 

 was discovered but recently in California in 1848, and 

 in Australia in 1851. A locality along the coast of Afri- 

 ca, opposite Madagascar, has been supposed to be the 



