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266 PRECIOUS STONES.
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Topaz
is of very wide distribution ; in England it is found with Cassiterite
at St. Michael's Mount; in Scotland water-worn crystals of the pale
blue (eau de nil) colour are found in gravels in Aberdeenshire ; and
bright though small crystals occur in the Mourne Mountain granite in
Ireland. Some of the Scottish specimens have been cut into very
beautiful stones, but these British occurrences are insignificant when
compared to some of the foreign ones. In the Ural Mountains near
Musinka blue crystals are found : these are sometimes known as Siberian
or Tauridan Topaz. Colourless specimens are found near Miask in the
Ilmen Mountains ; while in the district of Nerchinsk, in the
Adun-Chalon Mountains, very fine blue-green Topaz occurs ; and on the
Urulga River blue and yellow crystals are found, some of them of large
size, one in the Russian Imperial collection weighing 22-1/2 lbs. The
Urulga specimens are very prone to change colour on exposure to a
strong light. Topaz of various colours has been found in Kamshatka.
Brazil
is perhaps the most important locality. Here, in the State of Minas
Geraes, in the north-east, the gravels near Novas Minas afford
colourless and variously coloured specimens; of these the richer blue
ones are known as Brazilian Sapphire, and the deeper red ones, which
are very rare, as Brazilian Ruby. In the south-west of Minas Geraes,
near Curo Preto (Villa Rica), various shades of yellow are found in a
clay slate. The golden yellow crystals are known as Brazilian Topaz
from their abundant occurrence here.
In
Ceylon the gem gravels yield very fine Topaz in various shades of
yellow, and some colourless. The clear saffron yellow stones are known
as Indian Topaz,
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