Spinel: Magnesium
Aluminate. This mineral is chiefly valuable for furnishing the gem
stones cut from the transparent crystals, which afford as wide a range
of colors as is found in
any one mineral gem species. It is best known for the deep red gems
which are called "Spinel Rubies," which are of less value than
corundum rubies.
Stones
other than rubies are classed under the general name, Spinel, and may
be violet, rose, yellow, orange, green, or dull indigo-blue. The best
stones come from Ceylon, Burma and Siam.
Spodumene: Silicate
of Lithium and Aluminium. Silica 64%, Lithia 9%, Alumina 27%. This
mineral belongs to the Pyroxene group, occurring in prismatic crystals
and sometimes in massive form, greenish-white, grayish-white,
yellowish-green, emerald-green, and amethystine-purple in color.
Transparent to translucent.
Spodumene
is a rare semi-precious stone and is better known in its gem varieties,
Kunzite and Hiddenite. Kunzite is the light lilac-red variety from
California, and Hiddenite the emerald-green variety occurring at Stony
Point, North Carolina.
Steatite or This mineral usually occurs in flaky, foliated or mas-Talc: sive
forms, and in plates that appear to be tabular crystals. It also forms,
with chlorite and a few other substances, the rock called Soapstone,
which is a white, greenish yellowish, red or brown massive form. All
varieties are soft and all have a soapy feeling.
Ground
talc is used extensively as a lubricant, and as a toilet powder.
Soapstone, in slabs, is used to line acid vats and laundry tubs, also
for table tops, sinks, etc., in laboratories. It is also used in
electric switch Loards on account of its infusibility. Steatite is the
principal source of talc and soapstone and occurs in Virginia, New York
and Vermont-
Stephanite: Sulphide
of Silver and Antimony. Silver 68.5%, Sulphur 16 3%, Antimony 15.2%.
This comparatively rare mineral is an important ore of silver in some
camps, occurring massive, granular and as aggregates of small
crystals, color and streak iron-black. It is found in Saxony, Bohemia,
Hungary, Norway. England, Mexico and Chile; also in Nevada, Idaho and
Colorado, and is mined as an ore of silver.
