mineral

Orthoclase Feldspar

KAlSi3O8 (Potassium Aluminum Silicate)

AI-generated identification · may be incorrect

Hardness: 6 on Mohs scale; Color: typically pink, salmon, or peach-colored; Luster: vitreous to pearly; Crystal structure: Monoclinic; Cleavage: perfect in two directions at 90 degrees.

Hardness: 6 on Mohs scale
Color: typically pink, salmon, or peach-colored
Luster: vitreous to pearly

Identified July 12, 2026More mineral →

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Physical properties

Hardness: 6 on Mohs scale; Color: typically pink, salmon, or peach-colored; Luster: vitreous to pearly; Crystal structure: Monoclinic; Cleavage: perfect in two directions at 90 degrees.

Formation & geological history

Orthoclase is a major rock-forming mineral found primarily in igneous rocks like granite and pegmatites, as well as some metamorphic rocks. It forms from the cooling of magma or lava.

Uses & applications

Used in the manufacture of glass, ceramics, and enamels. Sometimes used as a gemstone (sunstone or moonstone varieties) and collected as a mineral specimen.

Geological facts

Orthoclase is the defining mineral for level 6 on the Mohs scale of mineral hardness. It is one of the most common minerals in the Earth's continental crust.

Field identification & locations

Identify in the field by its distinct pinkish/tan color, glassy luster, and 'step-like' 90-degree cleavage planes. Found globally in granitic terrains and riverbeds near igneous source rocks.