mineral
Orthoclase Feldspar
KAlSi3O8 (Potassium Aluminum Silicate)
Hardness: 6 on Mohs scale; Color: Pink, salmon, or peach; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Two directions at 90 degrees; Specific gravity: 2.55-2.63.
- Hardness
- 6 on Mohs scale
- Color
- Pink, salmon, or peach
- Luster
- Vitreous to pearly
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Physical properties
Hardness: 6 on Mohs scale; Color: Pink, salmon, or peach; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Two directions at 90 degrees; Specific gravity: 2.55-2.63.
Formation & geological history
Formed in igneous rocks like granite and syenite through slow cooling of magma, as well as in metamorphic rocks like gneiss. Found in pegmatites globally.
Uses & applications
Used primarily in the manufacture of glass and ceramics, as a filler in paint and rubber, and occasionally as a gemstone (moonstone variety).
Geological facts
Orthoclase is one of the ten defining minerals on the Mohs scale of mineral hardness. It was named from the Greek words for 'straight fracture,' referring to its two cleavage planes at right angles.
Field identification & locations
Identify in the field by its pinkish color, 90-degree cleavage, and hardness (it can scratch glass but is scratched by quartz). Commonly found in mountain ranges with high granite content.
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Other mineral specimens
Sandstone (with potential mineral staining/concretions)
Arenite (SiO2 based)
sedimentary
Schist
Schist
Metamorphic
Epidote
Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)
metamorphic
Gypsum (variety Selenite or Alabaster)
Calcium sulfate dihydrate (CaSO4·2H2O)
Mineral
Nephrite Jade
Nephrite
Mineral/Rock
Banded Gneiss (River Rock/Pebble)
Gneiss (specifically a banded variety often found as a river rock)
Metamorphic Rock