Microcline is one of the most common feldspar minerals. It can be colorless, white, cream to pale yellow, salmon pink to red, or bright green to blue-green. Microcline forms short prismatic or tabular crystals that are often of considerable size: single crystals can weigh several tons and reach yards in length. Crystals are often multiply twinned, with two sets of fine lines at right angles to each other. This gives a “plaid” effect that is unique to microcline among the feldspars. Microcline can also be massive. The mineral occurs in feldspar-rich rocks, such as granite, syenite, and granodiorite. It is found in granite pegmatites and in metamorphic rocks, such as gneisses and schists.
Polymorphism & Series: Dimorphous with orthoclase.
Mineral Group: Feldspar (alkali) group; (Si,Al) is completely ordered in low microcline.
Chemical Properties of Microcline
Physical Properties of Microcline
|Color||White, grey, greyish yellow, yellowish, tan, salmon-pink, bluish green, green.|
|Cleavage||Perfect on , good on |
|Mohs Hardness||6 – 6½ on Mohs scale|
|Specific Gravity||2.54 – 2.57|
|Density||2.54 – 2.57 g/cm3 (Measured) 2.56 g/cm3 (Calculated)|
Optical Properties of Microcline
|Optical Extinction||Inclined extinction to cleavage|
|Twinning||Carlsbad, Baveno, Manebach, polysynthetic on albite and pericline laws.|
|Optic Sign||Biaxial (-)|
|Birefringence||δ = 0.007 – 0.010|
Common in plutonic felsic rocks, as granites, granite pegmatites, syenites; in metamorphic rocks of the greenschist and amphibolite facies; in hydrothermal veins. A detrital component in sedimentary rocks and as authigenic overgrowths.
- The most important place of use is the production of porcelain.
- Microcline is used industrially in the production of glass and ceramic products.
- It is used as ornamental lapidary material with Amazonite in green color.
- Sometimes feldspar is also used in the manufacture of glass.
Quartz, sodic plagioclase, muscovite, biotite, hornblende.
A widespread mineral. Notable occurrences include:
- at FredriksvÄarn, Arendal, and Larvik, Norway.
- In the Ilmen Mountains, Ural Mountains, and on the Kola Peninsula, Russia.
- At St. Gotthard, Ticino, Switzerland.
- On Mt. Greiner, Zillertal, Tirol, Austria.
- At Baveno, Piedmont, Italy.
- In the USA, at Amelia, Amelia Co., Virginia; Haddam, Middlesex Co., Connecticut; and Magnet Cove, Hot Spring Co., Arkansas.
- In Colorado, in the Pikes Peak area, El Paso Co., Crystal Peak, Teller Co., with large crystals from the Devil’s Hole beryl mine, Fremont Co.; in the Black Hills, Pennington and Custer Cos., South Dakota.
- At Bancroft, Ontario, Canada.
- From Klein Spitzkopje, Namibia.
- In Brazil, from Minas Gerais, at Fazenda do Bananal, Salinas, Urucum, and Capelinha.
- At Ambositra, Madagascar.
- From Kimpusan, Yamanshi Prefecture, and Tanakamiyama, Otsu, Shiga Prefecture, Japan.
- At Broken Hill, New South Wales, Australia.
- Bonewitz, R. (2012). Rocks and minerals. 2nd ed. London: DK Publishing.
- Handbookofmineralogy.org. (2019). Handbook of Mineralogy. [online] Available at: http://www.handbookofmineralogy.org [Accessed 4 Mar. 2019].
- Mindat.org. (2019). Microcline: Mineral information, data and localities.. [online] Available at: https://www.mindat.org