Minerals and Cut Stones
Acadialite: An ordinary variety of Chabazite with a reddish color. In some specimens the coloring matter is arranged in a tasselated manner or in layers, with the angles almost
colorless. The best specimens are found in Nova Scotia.
Achroite: A colorless, transparent variety of Tourmaline occurring in the Island of Elba, Switzerland and Siberia.
Actinolite: A
Calcium-Magnesium-Iron Amphibole. This mineral is nearly always in long
acicular crystals without terminations. Color bright green or
grayish-green. Asbestos is a fibrous variety of Actinolite and occurs
principally in rocks that have been crushed and sheared under great
pressure. The Actinolite asbestos is used for the same purpose as the
Chrysotile variety but is regarded as less valuable. It is found in
Georgia and Idaho, (see Asbestos)
Adularia: A nearly pure Orthoclase. It is almost transparent and when polished is the Moonstone of the jewelers.
Agate:
A variegated Chalcedony, consisting of layers of Quartz, in which
slight amounts of impurities produce different colors in distinctly
defined layers. In the commonest Agates the colors are arranged in
bands. In others the colors are irregularly distributed, while in other
varieties the variation of colors is due to visible inclusions, as in
the Moss Agate.
Onyx
is a very evenly banded agate in which there is marked contrast in
colors. Cameos are onyxes, in one band of which figures are cut,
leaving another band to form the background. Agate is used for
ornamental and decorative purposes and also has a fluctuating popularity as a gem for artistic jewelry.
Alabaster: Hydrous
Sulphate. A variety of Gypsum that is white, colorless and transparent,
when pure; gray, red, yellow, blue or black when impure. Its crystals
occur around volcanic beds where they are produced by the action
