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PRECIOUS STONES
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animal, after the shape of a weasel, called "marten," of the species the "beech" or "common"' marten (mastela foina), found
also in Britain to-day. It is also interesting to note that the
various superstitions existing with regard to the different varieties
and colours of cats also exist in an identical manner with the
correspondim: colours of the minerals known as " cat's eye."
Several
varieties of cat's-eye have already been described. Another important
variety is that of the chryso-beryl called " cymophane." This is
composed of glucina, which is glucinum oxide, or beryllia, BeO, of
which there is 19.8 per cent., and alumina, or aluminium oxide, Al2O3, of which there is 80.2 per cent. It has, therefore, the chemical formula, BeO,Al2O3.
This stone shows positive electricity when rubbed, and. unlike the
sapphires described in the last chapter, which lose their colour when
heated, this variety of chrysoberyl shows no change in colour, and any
electricity given to it, either by friction or heat, is retained for a
long time. When heated in the blow-pipe alone it remains unaltered,
that is, it is not fusible, and even with microcosmic salt it requires
a considerably long and fierce heat before it yields and fuses, and
acids do not act upon it. Jt crystallises in the 4th (rhombic) system,
and its lustre is vitreous.
The
cymophane shows a number of varieties, quite as many as the
chrysoberyl, of which it is itself a variety, and these go through the
gamut of greens, from a pale white green to the stronger green of
asparagus, and through both the grey and yellow greens to dark. It is
found in Ceylon, Moravia, the Ural Mountains, Brazil,
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