mineral

Potassium Feldspar (Orthoclase)

Orthoclase (KAlSi3O8)

Presents a blocky, sub-rectangular shape with two cleavage planes meeting at nearly 90 degrees. Hardness 6 on the Mohs scale. Color is typically pink, flesh-colored, or tan. Luster is vitreous to pearly on cleavage faces. Crystal system is monoclinic.

Identified July 13, 2026More mineral →

Explore Potassium Feldspar (Orthoclase) in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Forms primarily in igneous rocks like granite and syenite through the crystallization of cooling magma. It is also found in metamorphic rocks such as gneiss and in some sedimentary sandstones (arkose). This specimen likely originated from the Pan-African basement complex common in southern Nigeria.

Uses & applications

Extensively used in the manufacture of glass and ceramics (porcelain, tiles). High-quality crystals (Moonstone) are used in jewelry. It is also a key component in scouring powders.

Geological facts

Orthoclase is one of the ten index minerals in the Mohs scale of mineral hardness. It belongs to the most abundant group of minerals in the Earth's crust, making up about 60% of terrestrial rocks.

Field identification & locations

Identified in the field by its distinct pinkish color, 90-degree cleavage, and hardness (cannot be scratched by a steel knife, but can be scratched by quartz). Very common in the granitic outcrops of South-South and South-East Nigeria.

Other mineral specimens

See all

Sandstone (with potential mineral staining/concretions)

Arenite (SiO2 based)

sedimentary

Sandstone with Mineral Veining or Crust

Sedimentary Sandstone (mostly SiO2 with Fe2O3 tinting)

sedimentary

Schist

Metamorphic

Gypsum (variety Selenite or Alabaster)

Calcium sulfate dihydrate (CaSO4·2H2O)

Mineral

Epidote

Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)

metamorphic

Nephrite Jade

Nephrite

Mineral/Rock