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GEMS.
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XII.
IVORY.
Although ivory
is an organic substance, and not mineral, yet writers on precious
stones do not fail to speak of it as an article which at all times was
largely used in works of art, and chiefly in ornaments of every kind.
Ivory
is well known to be the teeth of the elephant, among which some are so
large as to weigh two hunÂdred kilogrammes, to be about three metres
long, and to have at the base a circumference of almost seven hundred
and fifty millimetres. They are procured from Africa and the Indies.
The negroes wage a war of extermination against elephants for the sole
purpose of sending ivory to the Europeans.
In
art, ivory is divided into green and dry, exactly as in speaking of
timber for workmen. Articles in green ivory please the eye most,
because they are of a white but slightly greenish tint. Yellow ivory is
inferior in value to the white, because it shows the beginning of
decomposition : oxygenized muriatic acid and the steam and water of
slaked lime nearly restore yellow ivory to its original whiteness.
The ivory of the hippopotamus' teeth is very much valued, because it never loses colour.
Ornaments of most beautiful design in ivory have been obtained from the ancient tombs, but, on account
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