Almandine, almandite, Syrian garnet, essonite, cinnamon-stone, pyrope,
Bohemian garnet, vermeille, Cape garnet, Cape ruby, Arizona ruby,
American ruby, carbuncle, uwarowite, demantoide, grossularite, and
Bobrowska garnet are some of the scientific and commercial names for
different species and colors of the garnet group.
The crystallization of the garnet is isometric, refraction single,
specific gravity 3.15 to 4.3, hardness 5 to 8, lustre vitreous,
fracture uneven, colors red, violet, brown, yellow, green, and white,
and the various shadings of these colors.
Most varieties fuse easily to a brown or black glass; the uwarowite
fuses with borax to a clear chrome-green glass.
Syrian, almandine, almandite, and carbuncle are different names for the
iron-alumina garnet.
In colors, these stones shade from deep-red to violet and brownish-red,
and are composed of:
Silica 36.01
Alumina 20.06
Protoxide of iron 43.03
The specific gravity is 4. to 4.2, and hardness 7.5.
This garnet, sometimes called the precious garnet, is found in Ceylon,
Pegu, Brazil, Greenland, Hindustan, Bohemia, Tyrol, Œtzthal, Carinthia,
Styria, Switzerland, Ariolo, Canaria, Maggia, Hungary, Sweden, Norway,
Scotland, Spain, and the United States.
Grossularite, or lime-alumina garnet, is known in commerce as essonite,
or cinnamon-stone. The color is yellow, of various shades; specific
gravity 3.5 to 3.65, and hardness 6.5.
These stones are sometimes sold for jacinths, but they are softer than
the jacinth, and melt easily before the blow-pipe. Essonites come
principally from Ceylon, but are also found in other places.
Pyrope or Bohemian garnet is the magnesia-alumina variety, and is of
a uniform dark blood-red color. This stone is found in Bohemia, and
although quantities of small pieces are found, large specimens are
rare, and a piece that will cut into a four- or five-carat stone is
seldom met with and commands a high price.
These garnets are found at Stiefelburg by Meronitz, Triblitz,
Podsedlitz, and Neupaka.
The pyrope turns black under the blow-pipe, then red again, and melts
with difficulty into a black glass. With borax it melts to an
emerald-green glass. The specific gravity of this garnet is 3.69 to
3.78, and hardness 7.5.
Vermeille is a name given to the orange-red almandine, Cape garnet to
the bright red-yellow variety, Cape ruby to the pyrope, and American
ruby to the blood-red kind found in New Mexico, Montana, and Arizona.
Carbuncle is a term applied _to all_ garnets cut with a smooth rounding
top, sometimes called, after the French, cabochon.
Uwarowite or lime-chrome garnet is one of the rarest and most beautiful
of the garnet group.
The color of this stone is emerald-green, hardness 7.5, and specific
gravity 3.41 to 3.52. Uwarowites are found near Bissersk in the Urals
of Russia, but rarely in specimens of sufficient size to cut into gems.
This garnet is heavier and harder than the true emerald.
Demantoide or Bobrowska garnet is a soft garnet, olive-green to brown
and blackish-green in color, sometimes light green. It is found in
the Bobrowska River in the Urals. The specific gravity is 3.85,
and hardness about 6, its softness making it undesirable for many
ornaments. Before the blow-pipe it fuses into a black bead.
These garnets are often sold as olivines; they are heavier than
olivines and softer.
Demantoide is composed of:
Silica 35.44
Lime 32.85
Sesquioxide of iron 32.85
Magnesia .20