434 
Geology . 
d. Silver- giant This is one of the most common 
and abundant of the silver-ores, and there are but few sil- 
ver formations in which it does not occur in greater or 
less quantity. It occurs however, only in primitive 
mountains, and always in veins that principally traverse 
gneiss, mica-slate, and clay-slate, more seldom porphyry, 
and still more rarely granite. 
e. Red Silver-ore .-—This beautiful ore occurs in veins 
that traverse gneiss, porphyry, and grey- wacke. 
f. White Silver-ore. — It occurs in veins that traverse 
gneiss, and it continues to the greatest depths in these 
veins. 
g. Black Silver -ore, —It occurs in veins that traverse 
gneiss, porphyry, sienite, and grey- wacke. 
General Remarks. — The ores of silver are in general 
accompanied with calcspar and heavy-spar ; and from 
the preceding details, appear to occur principally in veins 
that traverse primitive and transition mountains. The 
greatest portion of the silver of commerce, however, is ob^ 
tained from argentiferous lead-glance, an ore that occurs 
more abundantly in the ficctz than the primitive moun- 
tains ; hence it is somewhat doubtful, whether or not sik 
ver may not be considered as a newer metal than its ores 
seem to intimate. 
14. Copper.— This metal is more widely distributed, 
and occurs in a greater variety of formations, than any of 
the preceding. Thus, it occurs in small quantities in a 
native state, disseminated through the granite of Corn- 
wall. The granite of that country, however appears to 
me, from the observations of Professor Playfair, to belong 
to the newest formation ; hence this native copper cannot 
wan and others, is silver-glance, — a mineral that does not possess the 
glassy aspect which so remarkably characterizes the conchoida! 
corneous silver-ore. 
