Alunite: Hydrous Sulphate of Aluminium and Potassium. Sulphur 38.6%,
Alumina 37%, Potash 11.4%. Sometimes called "Alum Stone" because after
repeated roasting, alum is obtained from it. It is a comparatively rare
mineral but is of considerable interest because of its utilization as
a source of potash. The compact varieties from Hungary are so hard they
are used for millstones.
It
occurs in hexagonal crystals, also massive with fibrous, granular or
porcelain-like structure. It is white, pink, gray or red, and has a
white streak; is transparent or translucent with a nearly pearly
luster. It is found in Italy, Wales, France, Greece, and in the United
States.
Amalgam: A
compound of Mercury and Silver. Silver 35%, Mercury 65%. It occurs in
crystals, in plates, coatings, and embedded grains; also massive. Color
and streak silver-white. It is opaque and gives a distinct silver
streak when rubbed on copper. When heated in tubes it yields a
sublimate of mercury and a residue of silver. On charcoal the mercury
volatilizes, leaving a silver globule. It is found in mines in which
veins of copper and silv/er cross each other.
Amazonite or: A variety of Feldspar found at Pikes Peak, Colo-
Amazonstone rado.
An apple-green Microcline which takes its name from the Amazon River,
though it is also found in Siberia, and in Colorado. It is used for
ornamental purposes and is manufactured into watch charms, umbrella
handles, etc.
Amber: Oxygenated
Hydrocarbon. In early times it was considered a simple resin, but it
is now fully ascertained that Amber and similar resins are of
vegetable origin, altered by fossilization. This is inferred by the
occurrence of insects incased in it, some of which appear to have
struggled after being entangled for in some specimens legs or
wings are found some distance from the body. Specimens with brilliant
colored bugs enclosed, are polished and used as charms.
The
darker shades of Amber are the most valuable, and while this substance
is outside the classification of gem materials, it is used for beads,
pendants, and small ornaments. Its greatest commercial value is in the
manufacture of mouthpieces for pipes, cigar and cigarette holders, etc.
Amber was known to the ancients and by them called Electrum on account of its electrical properties.
