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QUARTZ.
The quartz group, with all its divisions and ramifications, is so
large as to appall one. While so widely distributed over the earth's
surface as to seem a mineral of the most common kind, at its highest
and best its crystals rank as semi-precious stones, and even in its
various opaque forms it was greatly valued by the ancients, not only
as an ideal medium for their camei and intagli, but as a personal
decoration.
Quartz is 7 in hardness, specific gravity 2.6 to 2.7, and lustre
vitreous to resinous. Therefore its "gem" forms, cairngorm, smoky
quartz, citrine, frequently metamorphosed by heat into the so-called
Spanish topaz ; amethyst, rose quartz and rock crystal are in reality
harder than the opal, turquoise, peridot, to say nothing of coral
and pearl, classed with precious stones.
Under the head of compact quartz, succeeding the crystalline,
comes chrysoprase, translucent but not transparent, and always cut
en cabochon. It is of a lovely apple green color which, like the rose
quartz, upon long exposure to the light, is apt to fade.
After the compact quartz, of which chrysoprase is the star,
though "there are others," comes the long chalcedony group, with
its pretty spots and interesting bands, including onyx, agate, the
bloodstone and carnelian. Chalcedony might be said to be a pictorial
quartz, with markings for beauty instead of bright lustre. The
carnelian, a brownish-red variety of chalcedony, was called by the
ancients sard, and in its soft color and polish, exactly what such a
stone requires, was lovelier far than with the hard shine of to-day,
when it goes through all sorts of unnatural experiences at Oberstein.
Sardonyx is carnelian or sard in three distinct layers,
white and brown.
usually red,
The carnelian, or sardonyx, is the birthstone for August, in-
suring conjugal love. It gives courage and according to Marbodus :
Fate has with virtues great its nature graced.
Tied round the neck or on the finger placed,
Its friendly influence checks the rising fray,
And chases spites and quarrels far away :
That where the colour of raw flesh is found
Will staunch the blood, fast issuing from the wound :
Whether from mangled limbs the torrents flow
Or inward issues, source of deadly woe.
The mocha-stone of India, as well as our moss-agate, is of the
chalcedony group. Both are hard, tough and beautiful, and contain
green or brown mineral matter (oxide of iron) having an appearance
of vegetable growth, branches, leaves and moss, against the
water-white background of pure chalcedony. In a different way
it is as pleasing as jade, and even more durable, for jade is brittle.
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