5. Uvarovite.—It is emerald green due to chromium and forms small crystals with chromite. The crystals are too small to be of value as gems.
6. Andradite.—It has a varying composition and a variety of colours, (a) Topazolite
is transparent yellow and resembles topaz. (6) Demantoid is
grass-green. It has a high refractive index and dispersion greater than
that of diamond, and a facetted stone flashes brilliant prismatic
colours, (c) Melanite is the black variety. It has a very high
refractive index.
OCCURRENCE
Grossularite
occurs in metamorphosed impure limestone, and hessonite comes from
Ceylon in gravels associated with zircon. Pyrope occurs in the
diamondiferous rock in South Africa, and usually occurs in basic rocks,
such as peridotite and in serpentine. Spessartite occurs in granite,
quartzite, etc., in Ceylon, Madagascar and some other places and is
also associated with manganese ores. Almandine occurs in gneisses,
schists and a variety of rocks. The gem quality is found in India, and
Ceylon in gravels; South Australia; Minas Geraes, Brazil; Uruguay;
various parts of U.S.A., etc. Uvarovite is obtained principally from
the Ural mountains and in Quebec. Andradite occurs in
nepheline-syenite, serpentine, chlorite-schist, crystalline limestone
and stream beds.
In
India, garnet is found in a large number of places, but gem garnets
occur only in a few localities. In Bihar and Orissa, garnet is found in
the sands of the Mahanadi river. In Hazaribagh large garnets are found
in the mica, pegmatites and small ones in schists which are not of gem
quality. In Hyderabad, near Warangal, garnet occurs in gneiss. Some gem
quality garnet is also obtained which is largely used in Madras for
jewellery. In Madras garnet is found at Kondapalli in Kistna district
at Bezwada on the banks of the Kistna river; red garnets are obtained
in the
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