mineral

Microcline Feldspar

KAlSi3O8

Hardness: 6 on the Mohs scale. Color: Green, white, gray, yellow, or pink. Luster: Vitreous to pearly. Crystal structure: Triclinic. Cleavage: Perfect in two directions at nearly right angles (90 degrees). Specific gravity: 2.56-2.58.

Hardness: 6 on the Mohs scale
Color: Green, white, gray, yellow, or pink
Luster: Vitreous to pearly

Identified July 31, 2026More mineral →

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Physical properties

Formation & geological history

Forms primarily in felsic igneous rocks such as granites, granitic pegmatites, and syenites, as well as in metamorphic gneisses. Crystallizes directly from cooling magma or through hydrothermal processes.

Uses & applications

Used in the manufacture of ceramics, porcelain, glass, and as a dimension stone or decorative gemstone (especially the variety Amazonite).

Geological facts

Microcline is the low-temperature polymorph of potassium feldspar. It often exhibits cross-hatch twinning, which is a diagnostic microscopic feature distinguishing it from other feldspars.

Field identification & locations

Commonly identified by its blocky crystal habit, two cleavage directions meeting near 90 degrees, and its hardness. Found worldwide in pegmatite veins and granite intrusions.