GOLD. 169 
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 
dog 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 asever. Ifcontinued 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 hquid 
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. 
Il. MINERALS CONSISTING OF THE BASIC 
ELEMENTS WITH OR WITHOUT gh CI DIC— 
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 minerais valuable sources of gold. 
Native Goid. 
Isometric. In octahedrons, dodecahedrons ; without.cleav- 
age. Also in arborescent forms, consisting of strings of 
erystals, filiform, reticulated, in grains, thin lamine and 
masses. 
Color various shades of gold-yellow, becoming pale from 
alloy with silver; occasionally nearly silver-white from 
the silver present. Eminently ductileand malleable. H.= 
25-3. G.=12-20, varying according to the metals alloyed 
with the gold. Fuses at 2,016° F. (1,102° C.) 
