GOLD. 109 



filled to the level of the entrance with this gas. It is a com- 

 mon amusement for the traveler to witness its effect upon a 

 clog kept for that purpose. He is held in the gas awhile and 

 is then thrown out apparently lifeless ; in a few minutes he 

 recovers himself, picks up his reward, a bit of meat, and runs 

 off as lively as ever. If continued in the carbonic acid gas a 

 ■short time longer, life would have been extinct. 



Carbonic acid, under high pressure, becomes a liquid, and, 

 with pressure and cold, a white snow-like solid. In the liquid 

 state it is often found in microscopic globules in the inte- 

 rior of crystallized quartz, topaz, and some other minerals ; 

 and when this is true, calcite (calcium carbonate) is often 

 present in the same or an adjoining rock. 



Besides the calcium carbonate in nature, there are also 

 carbonates of ammonium, sodium, barium, strontium, mag- 

 nesium, iron, manganese, zinc, copper, lead, nickel, cobalt, 

 bismuth, uranium, cerium, and lanthanum. 



II. MINERALS CONSISTING OF THE BASIC 

 ELEMENTS WITH OR WITHOUT ACIDIC— 

 THE SILICATES EXCLUDED. 



I. GOLD. 



Gold occurs mostly native, being either pure, or alloyed 

 with silver and other metals. It is occasionally found min- 

 eralized by tellurium, making part of the valuable minerals 

 Sylvanite, Nagyagite and Petzite. It occurs often dissemi- 

 nated through pyrite and galenite in auriferous regions, 

 rendering these minerals valuable sources of gold. 



Native Gold. 



Isometric. In octahedrons, dodecahedrons ; without cleav- 

 age. Also in arborescent forms, consisting of strings of 

 crystals, filiform, reticulated, in grains, thin laminae and 

 masses. 



Color various shades of gold-yellow, becoming pale from 

 alloy with silver ; occasionally nearly silver-white from 

 the silver present. Eminently ductile and malleable. H. = 

 2*5-3. G. =12-20, varying according to the metals alloyed 

 with the gold. Fuses at 2,016° F. (1,102° C.) 



