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Its
specific gravity, greater than that of the jacinth of Ceylon, is from
4'38. In spite of its brightness, its light is more resinous than the
other. Under the action of the blow-pipe it does not melt, but loses
colour and becomes white.
Jacinths
have very often a defect which diminishes their beauty and value, viz.,
bubbles in the interior, of which no satisfactoiy explanation can be
given.
Some of an inferior quality, yellowish white, are found in Bohemia, Silesia, and Spain.
The
essonite and idocrasio were also called jacinth, but we cannot see the
reason, as they do not in any respect resemble that stone.
The
gem named by the ancients hyacinthus is a corundum, and not our jacinth
; we may rather believe that the latter was by them called lyncurium.
They
frequently used the lyncurium, pale and dark colour equalty, for
engravings and carnei ; but for this work they preferred the dark kind,
which, perhaps, was that which was called morio, on account of its mulberry colour, and of which Pliny says : ad ectypas seulpturas faciendas.
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