mineral
Orthoclase Feldspar
KAlSi3O8 (Potassium Aluminum Silicate)
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
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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.
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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
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