REFERENCE LIST OF THE MORE COMMON MINERALS.
Actinolite—a magnesium-calcium-iron amphibole (q.v.); commonly bright green to grayish green; crystals usually slender or fibrous.
Agate—a banded or variegated chalcedony (quartz, q.v.).
Alabaster—a fine-grained variety of gypsum (q.v.), either white or delicately colored.
Albite—a soda feldspar (q.v.), an aluminum-sodium silicate; H. 5–6; cleavage perfect in two planes; luster vitreous or pearly white; occasionally bluish gray, reddish, greenish; sometimes opalescent.
Amethyst—a variety of quartz of purple or bluish-violet color, due probably to manganese.
Amphibole—the type of an important group of rock-forming minerals known as the amphibole or hornblende group; a ferromagnesian silicate, monoclinic, H. 5–6; luster vitreous to pearly; fibrous varieties often silky; black, ranging through various shades of green to light colors; embraces the magnesium-calcium varieties, tremolite and nephrite; the magnesium-calcium-iron variety actinolite; the aluminous-magnesium-iron-calcium variety hornblende, and others.
Analcite—analcine, one of the zeolites; a hydrous aluminum-sodium silicate; luster vitreous, colorless, white; occasionally grayish, greenish, yellowish, reddish, transparent to opaque.
Andesine—a plagioclase feldspar (q.v.); a sodium-calcium-aluminum silicate, intermediate in composition between albite and anorthite; H. 5–6; white, gray, grayish, yellowish, flesh red; luster subvitreous, inclining to pearly.
Andalusite—an aluminum silicate; luster vitreous; whitish, rose red, flesh red, variety pearly gray, reddish brown, olive-green; H. 7.5, infusible; impurities sometimes so arranged in the interior as to exhibit a colored, crossed, or tesselated appearance in cross-section (chiastolite).