Tourmaline
as a gem stone is more valuable than Amethyst, and less than Topaz and
Aquamarine. It occurs in many localities among which are Brazil, the
Urals, Isle of Elba and Australia; also Maine, New York, Connecticut
and California.
Tremolite: Calcium-Magnesium
Amphibole. Silica 58%, Magnesia 29%. Occurs in crystals; often like
flax, or fibrous; also granular and massive, with color white to
dark gray. Its principal use is as a source of asbestos, (see Asbestos
and Actinolite).
Tridymite: Pure
Silica like quartz. A triclinic form of silica occurring in hexagonal
tables and presenting a pseudo-hexagonal aspect through the twinning of
three individuals. It also occurs in fan-shaped groups and spherical
rosettes. ,Is transparent, and colorless to white.
The
name is from the Greek, meaning "three-fold," in allusion to the common
occurrence of trillings It occurs in France, Transylvania, at Vesuvius;
and also in the Obsidian Cliff, Yellowstone Park.
Triphylite: A Phosphate of Iron, Manganese and Lithium, vary-Lithiophilite:
ing from the bluish-gray, Triphylite, with little manganese, to the
salmon-pink or clove-brown, Lithiophi-iite, with little iron. These
minerals occur in rounded crystals, massive and compact They are both
transparent to translucent and occur at various points associated with
other lithium compounds in the U. S. at Peru, Maine, in New Hampshire,
Massachusetts and Connecticut. At present these minerals possess small
commercial value.
Trogerite: Hydrous
Uranium Arsenate Arsenic Pentoxide 17.6%. Uranium Trioxide 65.9%.
Occurs in thin, lemon-yellow tabular crystals resembling gypsum
(crystals united in druses) with other uranium minerals near
Schneeberg, Saxony, and has been reported with Uraninite from the Bald
Mountain district, Black Hills, S. Dakota. It is interesting, as all
minerals containing uranium are, since the discovery of Radium.
Troostite: Zinc
Orthosilicate. An opaque, flesh-red or gray variety of Willemite. It
may also be honey-yellow, apple-green or brown, in color and occurs in
simple
crystals, massive, and in grains, at Sterling Hill and Franklin, New
Jersey, where it is mined as an ore of zinc.
Tungstite: Tungsten
Trioxide. Tungsten 79.3%, Oxygen 20.7%. Occurs rarely in crystals,
usually pulverant and earthy, with color from bright yellow to
yellowish-green. It is an important source of tungsten.
