white,
pink, reddish, yellowish, gray, bluish or green. Some specimens show a
bluish-white shimmer (Moonstone) and others a reddish sparkle
(Sunstone) due to enclosures of other metals. A large percentage of
the clays, is derived from decomposition of feldspars, including
Kaolin, an important material in the manufacture of pottery and
porcelain. Feldspars are used in the manufacture of fertilizers, as
fluxes to bind together grains of emery and carborundum in the making
of grinding and cutting wheels; in the manufacture of artificial teeth,
scouring soaps, and is a source of potash.
Fergusonite: An
ore of a brownish-black color, consisting of col-umbic acid and yttria,
with some oxide of cerium and zirconia. Occurs in pyramidal crystals,
and is sub-translucent to opaque. Named after Robert Ferguson of
Scotland.
Flint: TTiis
is more properly a rock than mineral. It is a very fine grained
crystalline aggregate of gray, red or black opal, chalcedony and
quartz. It is very hard, strikes fire with steel, and was extensively
used in prehistoric times for cutting implements.
Flos Ferri: A Calcium Carbonate variety of Aragonite in beautiful coralloidal form. The name is from the Latin, meaning "Flower of Iron."'
Fluorite Calcium
Fluoride. Fluorine 49%, Calcium 51%. TTiis is the principal source of
Fluorine, which when treated with sulphuric acid, gives fumes of
hydro-fluoric acid with which glass is etched. Fluorite usually occurs
transparent and is characterized by its fine color and handsome
crystals. Perhaps there is no other mineral known that can compare in
the beauty of its crystal groups. It may also be granular, massive and
fibrous, its color yellow, white, green, red, blue or purple. This
mineral occurs in beds, veins, and as crystals on the walls of cavities
in certain rocks. Handsome specimens come from Cumberland, England;
from Wales; from Norway and Saxony. In the United States the mineral
forms veins on Long Island, in Maine, Vermont, Connecticut and
Virginia. Beautiful crystal groups occur in Nova Scotia and Thunder
Bay. This mineral is used extensively as a flux in smelting iron and
other ores; in the manufacture of opalescent glass and enamelled ware.
The bright colored varieties are used for vases and cheap gems, the
transparent, colorless kind for lenses in optical instruments.
Fowlerite: A
zinciferous variety of Rhodonite, named after Dr. Samuel Fowler, of New
Jersey. It occurs as crystals in metamorphosed limestone associated
with zinc ores
at Sterling Hill and Franklin, N. J.
