MINERAL(S), a substance having a definite chemical composition and atomic structure and formed by the inorganic processes of nature. Minerals exhibit various properties, such as color, luster, crystal form, cleavage, fracture, hardness and density, which are used for identification and which exercise control on the commercial and industrial uses of the particular mineral. Small impurities in some minerals can result in varieties showing vastly different colors, e.g. varieties of corundum (aluminum oxide) include ruby (red), sapphire (blue), and oriental emerald (green). However, the possession of a definite chemical composition does not in every case suffice to fix a mineral species. Two (or more) minerals, such as diamond and graphite, which are carbon, can have the same chemical composition, but very different physical properties. This results from the way in which the constituent atoms are arranged. Where this internal atomic structure is expressed in the external form, the mineral is bounded by flat surfaces and is referred to as a crystal. From earliest times some minerals which occur as crystals have been sought after for their beauty, particularly their form and striking color (e.g. sapphire), or variegated colors (e.g. agate). Such precious or semi-precious stones (jewels and precious stones q.v.) were prized from earliest times (cf. Gen 2:12), used for ecclesiastical vestments and regalia (e.g. Exod 28), for trade (cf. Job 28:15-19) and to portray the nature of things to be (e.g. Rev 21:18-20). Other materials of the mineral kingdom were, and are, used by man in his everyday life—e.g. clay (Jer 18:4) and copper (Ezra 8:27) for liquid containers, iron for tools (2 Sam 12:31) and for vehicles (Judg 4:3) and the soil (Matt 13:8) for growing crops.

Bibliography H. H. Read, Rutley’s Elements of Mineralogy, 26th ed. (1970), 1-5.