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THE TOPAZ
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North.
America, and elsewhere. The cat's-eye of this is very similar to the
quartz cat's-eye, but a comparison will make the difference so clear
that they could never be mistaken, apart from the fact that the quartz
has a specific gravity considerably lower than the ehrysoberyl
cat's-eye, which latter is the true cat's-eye, and the one usually
understood when allusion is made to the stone without any
distinguishing prefix, such as the ruby, sapphire, quartz, etc., cat's
eye. It should, however, be mentioned that this stone is referred to
when the names Ceylonese and Oriental cat's-eye are given, which names
are used in the trade as well as the simple appellation, "cat's eye.'"
One peculiarity of some of these stones is that the "fire "' or "glow "
is usually altered in colour by the colour of the light under which it
is seen, the change of colour being generally the complementary. Thus,
a stone which in one light shows red, in another will be green : the "
eye " showing blue in one light will become orange in another : whilst
the yellow of another stone may show a decided jjurple or amethyst in a
different light.
A
good test for this, and indeed most precious stones, is that they
conduct heat more quickly than does glass, and with such rapidity that
on breathing upon a stone the wannth is conducted instantly, so that,
though the stone is dimmed the dimness vanishes at once, whereas with
glass the film of moisture fades but slowly in comparison.
The Topaz.
The name topnz is derived from the Greek topazes, which is the name of a small island situated in the Gulf
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