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Ch. 6: Ruby, Sapphire, Spinel etc.

Ch. 6: Ruby, Sapphire, Spinel etc. Page of 295 Ch. 6: Ruby, Sapphire, Spinel etc. Text size:minus plus Restore normal size   Mail page  Print this page
The Zircon, Hyacinth, or Jacinth. 139
in Egyptian mummy-pits, and the Greeks employed the stone for intaglios more than two thousand years ago.
THE ZIRCON, HYACINTH, OR JACINTH.
This gem belongs to the dimetric system of crystalli­zation, and is very imperfectly cleavable. Its specific gravity is 4.07 to 4.75 ; in lustre it is nearly adamantine,
although in the opaque varieties it is vitreous. It varies in colour from red to yellow, brown, green, grey, and white. Its fracture is conchoidal and brilliant. When heated it becomes phosphorescent, and loses its colour, and at the same time increases in specific gravity. If allowed to cool, however, when reheated the phos­phorescence does not reappear. This gem is unaffected by any acids except sulphuric after long maceration. Before the blowpipe it is infusible alone, but melts with borax into a transparent glass. Its chemical composition is—
The zircon or hyacinth is found in imbedded and attached crystals in granite, syenite, and gneiss, and also in beds of rivers associated with garnets in Ceylon,
Ch. 6: Ruby, Sapphire, Spinel etc. Page of 295 Ch. 6: Ruby, Sapphire, Spinel etc.
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