435 
Geology. 
be considered as reaching to the oldest rock of the primi- 
tive class. The gr^at quantities -of native copper found 
in the mines on the eastern side of the Uraiian mountains, 
and the masses in Brazil and Canada, originated from 
mica* slate, or more particularly from granular limestone 
that occurs in mica-slate ; hence, if my conjecture re- 
specting the granite of Cornwall be correct, these masses 
are of an older formation than the copper found in that 
granite. It occurs also in veins that traverse gneiss, mi- 
ca-slate, clay -slate, and grey-wacke ; and small portions 
have been noticed in serpentine-porphyry, and rocks be- 
longing to the newest fieetz-trap formation. 
a. Variegated Copper -ore, which is copper combined 
with sulphur and oxygen, occurs, in beds, in mica-slate 
at Rudolstadt in Silesia, Dognatska and Saska in the Ban- 
nat of Temeswar, and Roraas in Norway, It has also 
been observed in veins traversing gneiss, mica-slate, grey- 
Ivacke, and bituminous marl- slate. 
b . Copper-Pyrites . — It occurs in all the great classes 
of rocks, and sometimes in veins, sometimes in beds ; 
which latter are often of great thickness. The oldest 
formation of copper- pyrites, and indeed of copper in ge- 
neral, is that which occurs in beds in gneiss. It occurs 
also in beds in mica- slate, clay-slate, transition-rocks, and 
the oldest floetz-limestone. Very small portions of this 
ore appear in still newer formations : it occurs also in 
veins in primitive, transition, and old floetz-rocks, but is 
far more abundant in primitive than any of the other clas- 
ses of rocks. As it is the principal ore of copper, it fol- 
lows, that what we have stated respecting its age, is per- 
fectly expressive of the age of copper in general. 
15. Gold.— -Gold-yellow native gold occurs in masses, 
or in the form of sand, in the beds of many rivers. It 
would appear, that this alluvial gold is not derived from 
beds or veins, but from rocks through which it has b$ejt 
Vol. III. 5H 
