Microcline-Feldspar Mineral Specimen
HISTORY, NAME, LOCALITIES: Microcline was recognized as a mineral species in 1830. Its name stems from the Greek micros, meaning “small,” and klinein, or “slope,” and refers to a small inclination from 90 degrees between its cleavage angles. Microcline is abundant, with fine specimens coming from Malawi, Namibia, Pakistan, Italy, Argentina, and the United States (New York, New Hampshire, Pennsylvania, Colorado, and Oregon).
MINERALOGY, PROPERTIES, OCCURRENCE: Microcline [potassium aluminum silicate, KALSi3O8], pronounced MY-crow-kline, is a rock-forming mineral and the most common potassium feldspar. It is a tectosilicate or framework silicate that crystallizes in the triclinic system as frequently twinned, equant crystals with square cross sections. It has a Mohs hardness of 6.0, perfect cleavage in one direction, and a specific gravity of 2.56. Microcline is usually opaque to translucent, white to pale-yellow in color, and has a vitreous-to-dull luster. Most microline is formed at high temperatures during crystallization of magma or by deep metamorphism. It is a component of all silica-rich igneous and metamorphic rocks. Microcline also occurs in carbonatites, hornfels of contact metamorphic rocks, and granite pegmatites in association with albite and quartz.
METAPHYSICAL PROPERTIES, LORE, USES: Metaphysical practitioners believe that microcline stimulates clarity of thought, enhances general understanding, and improves one’s ability to cooperate with others. Microcline is mined for use in the manufacture of glass and ceramics. A rare, translucent, orange, gem variety that is included with hematite is known as “sunstone.”
COLLECTORS’ INFORMATION: Collectors value microcline for its rarity of well-formed and frequently twinned crystals.