Class : Silicates
    Subclass : Tectosilicates
    Crystal system : Triclinic
    Chemistry : KAlSi₃O₈
    Rarity : Ubiquitous

Microcline is a potassium feldspar dimorphic from orthoclase, with a perfectly ordered structure, which crystallizes at lower temperatures than this one. It is an essential mineral because it is very widespread as a major constituent of plutonic rocks (granites, syenites, granodiorites) and especially of their pegmatites, in which it is the most common feldspar. It is also the feldspar of metamorphic rocks (gneiss, anatexites, etc...). On the other hand, it is absent or very rare in volcanic rocks. Its name comes from the Greek mikros (small) and klinein (to incline) because of the slight deviation formed by the intersection of its cleavages in relation to 90°. Transparent to opaque, with a vitreous luster, microcline is colorless or white, yellowish, sometimes green to blue-green (amazonite variety). It forms crystals similar to those of orthoclase in their shapes and their twins, very often perthitic (exsolution of albite). The distinction between microcline and orthoclase is very difficult and almost always requires the use of X-ray diffraction. Microcline is a feldspar of interest in the porcelain industry. Mixed with clay and potash, ground microcline is the base of the glaze of porcelain and enamels. It is also used as an aluminous additive in the glass industry. A minor part goes into the manufacture of "soft" abrasives. The amazonite variety is used in ornamentation and jewelry.

Main photo : Microcline from Mas Sever Quarry, Catalonia, Spain © Jordy Fabre

Many twins are known for this mineral species such as the Carlsbad, Baveno, Manebach, and pericline twins without forgetting the polysynthetic twins.

No fakes recorded for this mineral species.