Chlorite—the type of an important group of secondary minerals usually characterized by a green color, softness and smoothness or unctuousness of feeling; they are usually aluminum-magnesium-iron silicates, with chemically combined water; derived from several other species, as pyroxene, amphibole, biotite, garnet, etc.; embraces a number of species, among which are clinochlore, penninite, prochlorite, and delessite.
Chromite—chromic iron; essentially an iron chromate; isometric; luster submetallic; iron black to brownish black; opaque; sometimes magnetic; resembles magnetite.
Chrysolite—olivine; essentially a magnesium-iron silicate; orthorhombic; H. 6–7; luster vitreous; green, commonly olive-green, sometimes yellow, brownish, grayish green; highly infusible; a common constituent of certain basic igneous rocks; the name olivine is more commonly used by geologists.
Chrysotile—a delicately fibrous variety of serpentine (q.v.).
Corundum—alumina; an oxide of aluminum; H. 9; rhombohedral; large crystals usually rough; luster vitreous; color blue, red, yellow, gray, and nearly white; purer forms of fine colors are sapphires; the red variety is ruby, the yellow, oriental topaz, the green, emerald, and the purple, amethyst; dark colors, with iron oxide, emery.
Delessite—a ferruginous chlorite, usually olive-green or blackish green; occurring commonly in the cavities of amygdaloids.
Diallage—a variety of pyroxene (q.v.); H. 4; characterized by thin foliæ; usually grayish green to grass-green, or deep green; luster on cleavage surface pearly, sometimes metalloid or brassy; an essential mineral in the gabbros, as sometimes defined.
Elæolite—a variety of nephelite (q.v.); occurring in large coarse crystals or massive, with greasy luster, from which the name is derived; a characteristic constituent of elæolite syenite.
Enstatite—one of the pyroxenes; essentially a magnesium silicate; orthorhombic; H. 5.5; luster a little pearly on cleavage surface; metalloidal in the bronze variety (bronzite); grayish white, yellowish white, greenish white to olive-green and brown; very infusible; a common mineral in certain basic crystalline rocks.
Epidote—a complex aluminum-calcium-iron silicate of varying composition; monoclinic; H. 6–7; luster vitreous, pearly, or resinous; color usually pistachio-green, or yellowish green to brownish green; can usually be detected by its peculiar pistachio hue, which is seldom found in other minerals; common in many crystalline rocks, usually as a secondary product.