The rich copper-ore of the Ural, which occurs in veins or masses,
amid metamorphic strata associated with igneous rocks, and even in
the hollows between the eruptive rocks, is worked in shafts. At the
bottom of one of these, 280 feet deep, has been found an enormous
irregularly-shaped botryoidal mass of _Malachite_ (Greek _malache_,
mountain-green), sending off strings of green copper-ore. The upper
surface of it is about 18 feet long and 9 wide; and it was estimated
to contain 15,000 poods, or half a million pounds, of pure and compact
malachite. Sir Roderick Murchison is of opinion that this wonderful
subterraneous incrustation has been produced in the stalagmitic form,
during a series of ages, by copper solutions emanating from the
surrounding loose and sporous mass, and trickling through it to the
lowest cavity upon the subjacent solid rock. Malachite is brought
chiefly from one mine in Siberia; its value as raw material is nearly
one-fourth that of the same weight of pure silver, or in a manufactured
state three guineas per pound avoirdupois.[33]