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gem, ornamental mineral or organic substance

(Encyclopedia)gem, commonly, a mineral or organic substance, cut and polished and used as an ornament. Gems also are used as seals (items of assurance) and as talismans (good-luck charms). For birthstones, see mont...

malachite

(Encyclopedia)malachite mălˈəkīt [key], a mineral, the green basic carbonate of copper occurring in crystals of the monoclinic system or (more usually) in masses. It is translucent or opaque; the luster is silk...

substance

(Encyclopedia)substance, in philosophy, term used to denote the changeless substratum presumed in some philosophies to be present in all being. Aristotle defined substance as that which possesses attributes but is ...

mineral

(Encyclopedia)mineral, inorganic substance occurring in nature, having a characteristic and homogeneous chemical composition, definite physical properties, and, usually, a definite crystalline form. A few of the mi...

feldspar

(Encyclopedia)feldspar fĕlˈspär [key], an abundant group of rock-forming minerals which constitute 60% of the earth's crust. Chemically the feldspars are silicates of aluminum, containing sodium, potassium, iron...

seal, stamp

(Encyclopedia)seal, stamp made from a die or matrix of metal, a gem, or other hard substance that yields an impression on wax or other soft substance. The use of seals is very ancient, examples of great antiquity o...

ironwork, ornamental

(Encyclopedia)ironwork, ornamental. The shaping of wrought iron, used almost exclusively until the 16th cent., is primarily an art of the blacksmith, who must work with the metal while it is at the desired stage of...

brasses, ornamental

(Encyclopedia)brasses, ornamental. Brass, a copper-zinc alloy produced since imperial Roman times, is closely associated in art with bronze, a copper-tin alloy (see bronze sculpture). Brass was generally fashioned ...

pearl, gem

(Encyclopedia)pearl, hard, rounded secretion formed inside the shell of certain mollusks, used as a gem. It is secreted by the epithelial cells of the mantle, a curtain of tissue between the shell and body mass, an...

pitch, substance

(Encyclopedia)pitch: see tar and pitch.