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Morgenthau Minerals and Cut Stones

Book Name: Minerals and Cut Stones

Author: Morgenthau

published: 1923

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Morgenthau 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.

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.