126 The Topaz.
deep
brownish-yellow hue, and are found in a soft loose sandy clay, which
renders the search for them an easy task. The crystals are usually not
large, seldom exceeding two or three inches in length; the terminal
pyramids are often beautifully modified, and the crystals are mostly
well defined. They are more or less striated longitudinally down the
prism. Associated with the topaz in this locality is sometimes found a
very rare mineral called euclase, which is of a pale blue or green
colour, somewhat similar to aquamarine.
Another
locality in the Brazils whence they come, is the district of Minas
Geraes; these topazes, found in rounded pebbles, are perfectly pure and
colourless, and are called "pingas d'agoa" or "gouttes d'eau;" they are
also termed Nova Minas; the Portuguese call them "slave diamonds."
These stones bear a much higher degree of polish than rock-crystal.
A
precisely similar topaz has been found in Tasmania, where some blue and
green ones have been discovered, but more water-worn than those of
other localities. Topazes of a fine pale blue colour are found in
Siberia, at Alabascka, near Murinsk, also at Odentochelong and Miask,
associated with quartz and beryl. They are found in tolerable plenty at
Altenburg, in Saxony, generally of a pure yellow colour; also in
Ceylon, Connecticut, U. S., Peru, Asia Minor, in England, Scotland,
Ireland, and the Hebrides.
Topazes are cut on a leaden wheel with emery, and polished with tripoli. The best form of cutting is the
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