SPINEL, GARNET, TOURMALINE, TURQUOISE, LAPIS-LAZULI, ZIRCON, CHRYSOLITE, CHRYSOBERYL, IOLITE, KYANITE,
APOPHYLLITE.
Spinel.—The name spinel is said to mean "spark," and is
so called, probably, from its pointed crystals in the form of
octahedrons. It has frequently passed for oriental ruby, but it
differs from that gem in its chemical nature, having for its
constituents alumina and magnesia with traces of certain
oxides in the colored varieties.
This precious stone affords a wider range of color than
almost any other, including all the prismatic hues with their
different shades and combinations, besides the colorless and
the black varieties; crystals occur from perfectly transparent
to nearly opaque. The kinds used for jewelry are spinel-ruby,
of pure red or crimson, tinged with blue or brown ; balas-ruby,
exhibiting a ruby-red diluted with rose or lilac ; rubicelle, yellow
or orange-red ; alntandine, of a violet hue ; and Ceylonite, or
pleonast, green and dark brown to black, steel-gray, or slate.
All these colors afford numerous gradations in shades.
Before its composition was understood, there was no distinction made between the spinel and the corundum ruby,
which accounts for the fact that so many of the celebrated
rubies, so regarded, have proved to be what are called by
modern mineralogists spinels. De Lisle, in 1783, was the
first scientist to distinguish between these different gems.
Both the spinel and the balas receive the name of ruby among
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