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Uses
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The
light coloured and flawless garnets are used as cheap gems and the rest
for abrasives. Garnet in the form of powder is a valuable grinding
agent for precious stones and is used in making emery paper. It is also
used for making pivot support of watches, etc.
Grades
1. Grossularite, hessonite
or cinnamon stone is the calcium garnet, which is reddish yellow in
colour and contains three to four per cent of iron oxide. It is lighter
coloured than the other varieties or may even be colourless. Various
shades of yellow and brown are met with. The terms 'hyacinth' and
'jacinth', applicable to a zircon have been wrongly used.
2. Pyrope.—It
is the best known of the gem garnets because of its beautiful ruby red
colour. It occurs with the diamond in South Africa, and is sold as Cape
ruby. It is cut in a faceted form and is sold as 'Bohemian garnet',
'Cape ruby', ' Elie ruby', etc. It occurs in grains and as stream
pebbles and not in good crystals. The colour varies from deep red to
black.
3. Spessartite.—It
is not much used in jewellery, as its colour (brown) is not popular.
The colour may also vary from brownish red to a dark red with a tinge
of violet.
4. Almandine.—It
was known to the ancients and called by them ' Carbunculus'. Its colour
varies from deep red to violet red and to black, but most of it is dark
and opaque and is used for abrasives. The transparent varieties are
used as gems. In artificial light it shows an orange hue. It can be
distinguished from red spinel by the pocket spectroscope. Facetted and
hollow cabochon forms are cut, which give a more attractive colour;
large quantities are being produced at Jaipur and Delhi. On some
carbuncles an interesting type of asterism may be noticed,
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