GLOSSARY - Archaeological Chemistry - page 496

maturity (of clay) The appropriate conditions created by the complex of tempera-
ture and time at which a clay mixture acquires specific properties such as plastic-
ity , hardness , and color .
medium A physical environment as, for example, a solid or liquid .
melting The physical process of a solid becoming a liquid ; see melting point .
melting point The temperature at which a solid liquefies; see freezing point .
mercaptan Generic name for foul-smelling organic substances consisting of, among
other components, a sulfur-containing group of atoms .
messenger RNA See RNA, messenger .
metabolism The whole range of physical and chemical processes by which living
organisms convert food into energy .
metal One of a large group of elements that are mostly solid at ambient tempera-
tures, have a shiny surface, and are good conductors of electricity and heat; only
eight metals were known in antiquity.
metal, base (1) The major component of an alloy; (2) the opposite of noble metal ,
that is, a metal such as iron, which is easily corroded .
metal, coinage Generic name for such metals as copper, silver, and gold, and alloys
of these metals, as for example bronze and electrum , whose chemical, physical, and
economic qualities make them suitable for coinmakings.
metal concentrate A metallic ore that has been dressed .
metal, native A metal that occurs naturally in irregularly shaped masses, uncom-
bined with other elements and can be worked by hammering, cutting, and/or
annealing ; see nugget.
metal, noble Generic name for the metals that are not corroded under any environ-
mental conditions as, for example, gold and platinum; see base metal .
metal, precious See noble metal .
metal, virgin See native metal .
metal leaf An extremely thin plate or leaf of a malleable, precious metal such as gold.
metallic materials Generic name for metals and alloys .
metalliferous Bearing or producing a metal .
metallography The study of the composition, structure, and properties of metals
and alloys , as revealed by the microscopic examination of their polished and etched
surfaces.
metalloid From the Greek words metallon (metal) and eidos (sort), an element whose
properties are intermediate between those of the metals and the nonmetals ; anti-
mony, arsenic, boron, germanium, polonium, silicon, and tellurium are metalloids.
metallurgy The science and technology of metals and alloys , including their extrac-
tion from mineral ores , working, and use.
metamorphic rock See rock , metamorphic.

metastable An apparently stable condition that may be perturbed to become

unstable.