PRECIOUS STONES 131
AMETHYST
So called on account of its supposed preservative powers against intoxication.
It is crystallized quartz, or a colored rock crystal, found in Siberia, India, Brazil, Uruguay, and the United States.
Crystallization hexagonal, occurring in six-sided prisms more or less modified and terminating in pyramids.
Hardness, 7; specific gravity, 2.6 to 2.J.
Lustre vitreous; transparent to translucent.
Cleavage
none or very indistinct; it may sometimes be discovered by heating the
crystal and plunging it in cold water. Fracture conchoidal, glassy.
Doubly refractive (index, 1.55 and 1.54); twin colors, reddish and bluish purple.
Sections at right angles to optic axis show circular polarization.
It is composed of silica, colored probably by oxide of manganese.
Heat
changes color to a more or less yellowish tinge, turning to greenish at
high temperature, and colorless at 250° F., and sometimes makes it
opalescent. It is infusible before the blow-pipe, but dissolves if
heated with carbonate of soda. It is not attacked in any way by the
three acids.
Color,
pale to deep violet and purple, some shades of the latter being
especially rich and beautiful. The color is often distributed very
unevenly through the stone. Sometimes another color—yellow or green—is
found in connection with the natural purple in the crystal.
Usually cut step; often cut brilliant in the finer qualities.
The name is used in heraldry to designate the purple color on escutcheons of noblemen.
Symbolizes deep and pure love, February, Matthew the Apostle.
