Formula: K(AlSi3O8) tectosilicate (framework silicate)
Microcline is a K-feldspar.
Amazonite is a variety of microcline
Adularia is a more ordered low-temperature variety of orthoclase or partially disordered microcline.
Hyalophane is a barium-rich variety of microcline or orthoclase.
Properties of microcline:
Specific gravity: 2.54 to 2.57
Hardness: 6 to 6½
Colour: White, blue, green, pink, yellow
Solubility: Insoluble in water, hydrochloric, nitric and sulphuric acid
Microcline occurs mainly as a primary mineral in
schist and gneiss. K-feldspars are essential
granite, and microcline is the common
pegmatites. In sedimentary rocks microcline is present in
Microcline is characteristic of the granulite facies and it is also a mineral of the albite-epidote-hornfels, hornblende-hornfels and pyroxene-hornfels facies.
At Broken Hill, New South Wales, Australia, microcline variety hyalophane has been described from lenses and streaks in acid gneiss.
At the Kaso mine, Japan, microcline variety hyalophane occurs in veins with manganese-rich tremolite, rhodonite, rhodochrosite and spessartine.
In the manganese ores of Otjosondu, Namibia, hyalophane is found in a rock consisting mainly of calderite, and it also occurs as small veinlets in the calderite.
At Slyudyanka, Siberia, Russia, microcline variety hyalophane occurs in phlogopite-calcite veins in a pyroxene-amphibole gneiss.
At the Little Gem amethyst mine, Jefferson county, Montana, USA, microcline is ubiquitous, intergrown with other feldspars and quartz. Many of the microcline crystals are Baveno twins, and less commonly Manebach twins. Alteration products include muscovite variety sericite and kaolinite.
Common impurities in microcline: Fe,Ca,Na,Li,Cs,Rb,H2O,Pb
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