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MALACHITE.
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143
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Corsi states, though with hesitation, that the molo-chites was
our malachite;* whilst King affirms, that under the same name the
ancients understood a kind of plasma, and not the carbonate of copper,
which he says the Romans called chryso-colla, from its use in soldering
gold.j
If
the chryso-colla is really the stone now known as malachite, it must
have heen very common in the time of Nero, who once caused the arena of
the circus to be strewn with the powder of the chryso-colla, wishing
thus to show favour to the green party.
The
principal beauty of the malachite consists in the brightness of its
colours. It is an oxygenized carbonate of natural copper.
It
is divided into two kinds : the fibrous and the compact. The fibrous
malachite is of a uniform colour of perfect emerald green. It is found
in crystals of acute-angled prisms of three faces. Its crystals are
needle-pointed and very thin. Its specific weight is 3-66.
It presents, with diversified veining, beautiful spots in deep but
brilliant green. When polished, it has a delicate, hut, generally,
resinous light. Its breakage is rough and bright. It decomposes in
acetic acid, and communicates to it a dark green colour. It blackens
only over burning coals, but crackles, becomes quite black, and at last
leaves a button of pure copper under the irresistible action of the
blow-pipe, having lost much of its weight.
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