fibres
spun from a bead of molten Quartz are used to suspend the magnets in
delicate galvanometers, since they allow the magnets to return very
readily to the position of rest when no current is passing. The Chinese
make buttons of it.
In
ancient times it was highly valued, especially perhaps by the Romans,
for the production of vases and cups, some of which were of remarkable
size, for it is recorded by Ben Mansur that at the capture of Ghasna in
1159 four vases made of Rock Crystal were found, each of which would
hold two skinfuls of water. Pliny records that the material then used
came from the Alps, and at that time it was believed to be water frozen
so hard that it could not be thawed at ordinary temperature; this is
said to have led the Romans to only use it for cold liquids. One of the
most beautiful pieces of work in this material was a vase belonging to
the French Kings ; it was 9 inches high and 9-1/2 inches in diameter, and was carved with figures illustrating the intoxication of Noah. It cost some £4,000.
The
Indians used the material also in the production of imitations of the
rarer gems, for this purpose staining it in various ways; but though
these methods seem to have been known to Pliny, he declines to record
them, on the ground that they were fraudulent. Dutens ("Pierres
Precieuses") states that the methods were as follows : The Rock Crystal
was made red hot and then plunged into various coloured solutions. By
this means innumerable minute cracks were produced, into which the
coloured liquid penetrated. The colours used were: for Ruby, tincture
of cochineal; for Topaz, tincture of saffron; for Sapphire, tincture of
Turnesol; for Amethyst, the juice of Nerprum ; by using both Turnesol
and saffron, an emerald-green was produced.
