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diopside, malacolite, salite, coccolite, augite, etc. They are all silicates of lime and magnesia with sometimes alumina and iron. Pyroxene is an essential constituent of many rocks, especially basic igneous rocks, as basalt, gabbro, etc.

and micaceous structure, belonging to the chlorite group; a hydrous silicate of alumina, magnesia, and iron; -- called also clinochlore.

A hydrous silicate of magnesia and aluminia. It occurs in soft, soapy, amorphous masses, filling veins in serpentine and cavities in trap rock.

An antacid, as magnesia, used to correct acidity of the stomach.

A mineral or rock consisting chiefly of the hydrous silicate of magnesia. It is usually of an obscure green color, often with a spotted or mottled appearance resembling a serpent's skin. Precious, or noble, serpentine is translucent and of a rich oil-green color.

To convert (a magnesian silicate) into serpentine. -- Ser`pen*tin`i*za"tion, n.

d black, the red variety being the gem spinel ruby. It consist essentially of alumina and magnesia, but commonly contains iron and sometimes also chromium.

A crystalline mineral found in guano. It is a hydrous phosphate of magnesia and ammonia.

hitish, or grayish color, usually occurring in foliated masses. It is hydrous silicate of magnesia. Steatite, or soapstone, is a compact granular variety. Indurated talc, an impure, slaty talc, with a nearly compact texture, and greater hardness than common talc; -- called also talc slate.

e consisting of burnt gypsum, aluminium silicate (kaolin), or some similar ingredient, as magnesia. It is sometimes used to adulterate certain foods, spices, candies, paints, etc. -- Terra cotta. Etym: [It., fr. terra earth + cotta, fem. of cotto cooked, L. coctus, p.p. of coquere to cook. See Cook, n.] Baked clay; a…

olor, rarely sulphur yellow and blue. It is a silicate of alumina and lime with some iron magnesia, and is common at Vesuvius. Also called idocrase.

A fluophosphate of magnesia, occurring in yellowish crystals, and also in massive forms.

s imbedded in limestone near Warwick, New York. It consists of the borate and titanate of magnesia and iron.

The upper division of the Permian (Dyas) of Europe. The prevailing rock is a magnesian limestone.