feldspars
121loess — loessial, loessal, adj. /loh es, les, lus/, n. a loamy deposit formed by wind, usually yellowish and calcareous, common in the Mississippi Valley and in Europe and Asia. [1825 35; < G Löss < Swiss G lösch loose, slack (sch taken as a dial.… …
122mica — micalike, adj. /muy keuh/, n. any member of a group of minerals, hydrous silicates of aluminum with other bases, chiefly potassium, magnesium, iron, and lithium, that separate readily into thin, tough, often transparent, and usually elastic… …
123microcline — /muy kreuh kluyn /, n. a mineral of the feldspar group, potassium aluminum silicate, KAlSi3O8, identical in composition with orthoclase but having triclinic instead of monoclinic crystals, used in making porcelain. [1840 50; MICRO + cline < Gk… …
124mining — /muy ning/, n. 1. the act, process, or industry of extracting ores, coal, etc., from mines. 2. the laying of explosive mines. [1250 1300; ME: undermining (walls in an attack); see MINE2, ING1] * * * I Excavation of materials from the Earth s… …
125norite — noritic /naw rit ik/, adj. /nawr uyt/, n. a granular igneous rock consisting of a mix of light and dark minerals, the former being calcic plagioclase feldspars, and the latter orthorhombic pyroxenes. [1875 80; < Norw norit. See NORWAY, ITE1] * *… …
126opal — /oh peuhl/, n. 1. a mineral, an amorphous form of silica, SiO2 with some water of hydration, found in many varieties and colors, including a form that is milky white. 2. an iridescent variety of this that is used as a gem. 3. a gem of this. [1350 …
127Opal — /oh peuhl/, n. a female given name. * * * A hydrated, noncrystalline silica mineral used extensively as a gemstone. Its chemical composition is similar to that of quartz but generally with a variable water content. Pure opal is colourless, but… …
128orthoclase — /awr theuh klays , klayz /, n. a common white or pink mineral of the feldspar group, KAlSi3O8, having two good cleavages at right angles, and found in silica rich igneous rocks: used in the manufacture of porcelain. [1840 50; ORTHO + clase < Gk… …
