QUARTZ AND ITS VARIETIES.
Crystalline system—Hexagonal when crystallized.
Hardness—7.
Specific gravity—2'5—2'8.
Lustre—Vitreous.
Composition—Silica, SiOg. Silicon or Silicium = 46'67, oxygen = 53'33 per cent.
The
most transparent and vitreous varieties of the quartz family are known
as rock crystal, and have been used very largely for many purposes in
all ages. Bock crystal was considered of great importance for
ornamental purposes during the cinque-cento period. At the present time
its greatest value is for optical purposes, administering to the
comfort of a large number of the human race. It is also largely used in
the cheaper kinds of jewellery, and is known by the various names of
Bristol, Welsh, Irish, Cornish, and Californian diamonds. It is also
known and employed in jewellery under the name of " white stone."
Its
original name of crystal was given to it because of its supposed origin
from ice. Claudianus, one of the writers of antiquity, calls it " ice
hardened into stone." Orpheus calls it " the translucent image of the
Eternal Light," and suggesfs its use as a burning glass to light the
sacrificial flame. The natives of India believed it to the mother or
husk of the diamond, and called the diamond the ripe and the crystal
the unripe diamond.
Sir Thomas Browne, in his work on Vulgar Errors, 1G1G,
says that the opinion was then prevalent that the crystal was congealed
ice. The word crystal, by being derived from the Greek Krustallos, meaning ice, stamps the fact indelibly upon the history of this stone.
The
Romans were particularly partial to rock crystal, and employed it
largely for articles of household use, as well as for personal
adornment. They paid large sums for vessels made of it, and the art of
forming these from such a material reached at that time a very high
state of perfection. Of the patient labour necessary to the delicate
task of hollowing out vessels of such a character, it is difficult to
form an estimate.
The
various museums of Europe contain valuable collections of crystal cups,
vases, goblets, &c, showing that at one time these articles were
brought into extensive use. A crystal ewer in the South Kensington
Museum, and for which £450 was paid, is 8-1/2 inches high, and has a
diameter of 5-1/2 inches. It belongs to the 9th or 10th century, and is
carved in low relief, with birds, animals, and foliage. By an inventory
made in Paris in 1791, the crown jewels of France contained crystal
goblets, vases, &c, some of which were beautifully
engraved, and were altogether valued at one million francs. One urn,
measuring 9^ inches in diameter, and 9 inches high, was engraved with
the figure of Noah asleep, his children holding a covering. This urn
cost £1,000.
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