MALACHITE
(Green Carbonate of Copper)
Is
a hydrated carbonate of copper, found in the upper parts of copper-ore
deposits in the Urals, South Australia, and the United States.
Crystallization monoclinic; usually botryoidal or stalag-mitic; structure finely and firmly fibrous.
Hardness, 3.5 to 4; specific gravity, 3.7 to 4.
Lustre adamantine to vitreous; crystals translucent.
Composition: copper oxide, 71.9; carbon dioxide, 19.9; water, 8.2.
It
dissolves with effervescence in nitric acid, blackens under the
blow-pipe, fusing with borax to a deep green globule, and ultimately
affords a bead of copper.
Color,
a bright green with lines of a darker shade, showing, by its
concentric structure, evidence of deposition from a solution in water,
of successive layers.
When used for jewelry it is usually cut flat or en cabochon, or
pear shape for pendants. It is seldom used for gem purposes in the
United States, except in connection with azurite, with which it is
sometimes found in combination. Cut en cabochon across these
alternate layers, a beautiful mottled effect is produced. But little of
this combined form of the mineral is to be had now, as most of it was
melted for copper before it came into vogue for jewelry.
