Rhodolite: A
variety of Garnet consisting of two parts Pyrope and one part
Almandite. It is pale rose or purple in color and used as a gem stone.
Occurs in Macon County,
Georgia
Rhodonite: Pure
Manganese Silicate. Silica 46%, Manganese 54%. It occurs in crystals
possessing many habits of which the cubical, tabular and columnar are
the most common though it also occurs as structureless or granular
masses. Color light brownish-red, flesh-red and rose-pink; sometimes
greenish, yellowish or even black when impure and from exposure. Fine
crystals of Rhodonite are found in Sweden, and associated with zinc
ores at Franklin, N. J.
The
attractive rose-pink color imparted by the manganese, has led to the
utilization of this mineral as an ornamental stone. Much of its beauty
depends on the matrix effects brought out by the contrast of the deep
rose-red Rhodonite with its accompanying minerals. It is essentially a
Russian ornamental stone, the raw material being derived from Siberia.
The transparent red varieties are used to some extent as a gem stone,
the gem material occurring in California and Montana.
Riebeckite: Iron-Sodium
Amphibole. This mineral occurs only in embedded prisms showing no
terminations. It is black, vitreous and very pleochroic in green or dark
blue tints, that is, exhibiting different colors when viewed in different
directions. It occurs on the Island of Socotra in the Indian Ocean,
also in Corsica and Scotland.
Rock Crystal: A
pure, colorless, transparent variety of Quartz, forming distinct
crystals, including the variety called "Lake George Diamonds" found in
Herkimer County, New York.
Before
glass manufacturing was discovered, Rock Crystal was much used for the
carving of transparent objects such as cups, vases, and small
ornaments. This art is still practiced in Japan, where the native
lapidaries fashion wonderfully symmetrical polished spheres. Rock
Crystal is also cut into brilliants, which when set in cheap jewelry
are more durable and brilliant than glass-imitation diamonds. It is
also made into faceted beads and pendants.
Roepperite: Iron-Manganese-Zinc
Chrysolite. It occurs in large coarse crystals, orthorhombic in habit.
Color when fresh, pale yellow; when weathered, dark green to
black. Slightly magnetic. Occurs with Willemite, Franklinite, and
Spinel at Sterling Hill and FranLlin Furnace, N. J.
FIFTY-NINE
