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Mountains Of Kernhausen Whence It Is Sometimes Called Hungary Green

It is prepared from malachite, a beautiful copper ore employed by
jewellers, and is a hydrated dicarbonate of copper, combined with a
white earth, and often striated with veins of mountain blue, to which it
bears the same relation that green verditer bears to blue verditer. The
colour, which may be extracted from the stone by the process followed
for native ultramarine, varies from emerald-green to grass-green, and
inclines to grey. It has been held in great esteem by some, and
considered strictly stable, on the assumption, probably, that a pigment
obtained from a stone like ultramarine, and by the same method, could
not be otherwise than permanent. That it is so, with respect to light
and air, there is no denying; but the green, when separated from the ore
and purified for artistic use, is merely a carbonate of copper, and
therefore subject to the influence of damp and impure air, in common
with other non-arsenical copper colours. As a pigment, native malachite
green has the same composition, or very nearly the same, as that which
can be artificially produced, and answers to the same tests. Water-rubs
of the two varieties which we exposed to an atmosphere of sulphuretted
hydrogen became equally blackened by the gas. Practically, there is
little or no difference between them: both preserve their colour if kept
from damp and foul air, both are injured by those agents, and both are
liable to darken in time, especially when secluded from light. The
artificial, however, can be obtained of a much finer colour than the
natural, which it may be made to resemble by admixture with mineral
gray. On the whole, they can scarcely be recommended for the palette,
and are certainly inferior in durability to Scheele's and Schweinfurt
greens. In fresco painting they have been pronounced admissible; but,
apart from the question of damp, we should deem the conjunction of lime
with carbonate of copper not favourable to permanence. By the action of
alkalies, even the native green malachite may be converted into blue;
and it becomes a question whether the dingy greenish-blue on some
ancient monuments was not originally malachite green.


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