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become
colourless and due to their lustre, they are known as ' Matura
diamonds' from Ceylon. Zircon is also used for the manufacture of
zirconium oxide, a highly refractive material suitable for crucibles',
etc., and for preparation of metallic zirconium.
Gem varieties
1. Hyacinth and jacinth—clear, transparent, yellow, orange, red and brown—formerly also applied to blue stones.
2. Jargon includes other colours.
3.
Matura diamond is zircon from Matura, Ceylon. It is naturally
colourless or rendered colourless by heat treatment.
4. Blue zircon is getting popular in recent times.
OCCURRENCE
Zircon
is a common accessory mineral occurring in many granites and gneisses.
It occurs in Travancore in some coastal sands (zircon sand). Gem
quality stones are found as pebbles and water-worn crystals in alluvial
deposits in Ceylon, Siam and Indo-China. Ceylon and Indo-China are the
most important localities for gem zircon, which also occurs in
Tasmania, New South Wales and New Zealand. Blue zircon is found in
Indo-China.
The
Ruby Mines of Burma also produce some transparent brown zircons. Pale
or straw-yellow and colourless zircons come from Ceylon and are cut as
gems. It's also occurs in small quantities in nepheline syenite near
Kangayam, Coimbatore district, and in Travancore in pegmatite veins
associated with chamockite in Eraniel taluk, in pegmatites in Kadavur,
Trichinopoly district; and in the Seitur graphite mine, Ramnad, Madras
Presidency; and near Domchanch, Hazaribagh district. Some dark brown
crystals were also obtained from Abraki Pahar, Gaya district, Bihar.
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