Uses
The
yellow and colourless precious topaz is most often used as a gem. It is
cut in brilliant form in Mogok and is called 'Mogok diamond'. In India
it has been called ' Pushparagam'. The step cut is used at times—all
specimens sufficiently transparent, finely coloured and free from
faults are used as gems. Inferior stones are crushed and powdered for
use as grinding material.
Occurrence
Gem topaz is largely obtained from Brazil. It is found in the Ural mountains and Miask, the Ilmen mountains.
Blue topaz has been obtained from Caingorm, Banffshire, Scotland and a
few other places. Good crystals also occur in the tin mines of Saxony
and Cornwall; and in Ceylon, Japan, Mexico and Tasmania. , It usually
occurs in gneisses, schists, granites and pegmatites, and is usually
the product of pneumatolysis by the action of gases containing fluorine
and watery vapour from igneous intrusions, often accompanied by beryl
and cassiterite. Topaz as a gem-stone was known in India from very
ancient times. It is found in the Tavoy district, Burma along with tin
and wolfram in mines. At times pellucid water-worn crystals of topaz
are found in the gem-gravels of Mogok. Very fine specimens of topaz
were obtained from the great pegmatite dyke of Sakangyi in the Mogok
Stone tract. There was extensive mining in this area about 1923 for
rock crystals; along with it the topaz crystals were also obtained.
Exceptionally large crystals were obtained here. In Mogok it forms a
cheap stone, and is sold as Mogok diamonds. Its usual associates are
tourmaline, quartz, fluorite, apatite, beryl and other ores of
tungsten. It also occurs in placer deposits. In Ceylon it forms
colourless water-worn pebbles.
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