Chlorastolite
is a pink fibrous variety, occurring as pebbles on the shores of Lake
Superior, and is used as an ornamental stone. Ozar-kite is a white,
massive variety found in Arkansas, in the Ozark Mountains. It also
occurs in Scotland, Sicily, Bohemia, and in Iceland as straw-yellow
needles, called Carphostilbite.
Thulite:
A rose-red, fragile variety of Zoisite, one of the Epidote group of
minerals. It is named after "Thule," ancient name in Norway, where it
occurs.
Tiger-Eye: A
delicate, fibrous, yellow to brown variety of Croci-dolite. It occurs
in South Africa, is used as a semiprecious stone in jewelry, and is
made into paperweights, paper-cutters and ornaments.
Tin: A
metal of brilliant white color, occurring mostly as an oxide and not
very abundant. It is used chiefly in coating other metals, especially
iron, in the manufacture of tin-plate. The
mineral, Cassiterite, containing 79% tin, is the chief source of this
metal.
Titanite or Silica 30.6%, Titanium Dioxide 40.8%, Lime 28.6%. Sphene: Iron is present in varying amounts and sometimes man-
ganese.
Occurs usually in crystals, but in some places in granular and compact
masses. The crystals are wedge-shaped, envelope-shaped, prismatic and
tabular. This mineral is brown, gray, yellow, green, black, rose or
white, being pleochroic in yellow and pinkish tints.
Titanite
is opaque, in black or brown color, and Sphene is translucent, yellow
or green. The rose-red variety is called Greenovite.
The
green varieties, when transparent, are used as a gem stone, the index
of refraction being higher than that of any other gem stone except the
diamond, lending great brilliancy to the cut gem. The gem material,
however, is very difficult to obtain. Particularly fine crystals are
found in Piedmont, Italy; in Tyrol; also in Maine, New York, and North
Carolina.
Topaz: Silicate
of Aluminium containing Fluorine. A semi- precious stone that occurs
in nature in distinct and handsome crystals, and in a massive form, is
pyro-electric and frequently exhibits optical phenomena. This mineral
is honey-yellow, yellowish-red, rose and bluish-green in color,
although the yellow shades are generally accepted as the typical Topaz
colors.
When
cut it exhibits much brilliancy, which together with its hardness,
gives it value as a gem stone. Topaz is obtained from many localities,
but the best colored stones come from Brazil.
