ceives various forms, such as the step and table cut. If of a pure color, it is set d jour, otherwise
with a foil corresponding to its color; but the electric schorl is
sometimes set so that it can be removed from its mounting to be used in
performing experiments. The value of tourmaline depends upon its
color, purity, and size. The siberite and rubellite stand highest in
estimation. A siberite, as large as"five lines, is worth about one
hundred and fifty dollars; and one of four to twelve lines, good color
and pure, is worth about fifteen hundred dollars. The rubellite from
Paris, Maine, has become very rare, and it is much to be regretted that
no more attention is paid to obtaining a fresh supply, as the crystals
are of an exceedingly fine purple color, and perfectly transparent. I
have a few polished rubellites and green tourmalines in my cabinet,
which I value equally as high as any gems.
The
dark-green tourmalines, six. lines long and four broad, are sold in
Paris for eighty francs, and the light-green, of the same size, for
forty francs. The most splendid siberite is at the British Museum,
having been presented by the King of Ava to Colonel Symes; it is
valued at one thousand pounds sterling.
Tourmalines
may be readily distinguished from other gems or pastes, which are
sometimes substituted for them, by their property of assuming polaric
electricity after being heated.
QUARTZ,
This
mineral is diffused all over the globe. Its varieties are very
numerous, and many of them are employed in jewelry and for divers
ornamental purposes. It occurs massive, in concretions, in confused
crystalline masses, and in crystals, of which the form is the six-sided
prism, terminated by six-sided pyramids; also the dodecahedron, or
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