mineral
Orthoclase Feldspar
K(AlSi3O8)
Hardness: 6 on Mohs scale; Color: typically pinkish-orange, peach, or white; Luster: vitreous to pearly; Crystal structure: Monoclinic; Cleavage: two planes at nearly 90 degrees; Specific gravity: 2.55-2.63
- Hardness
- 6 on Mohs scale
- Color
- typically pinkish-orange, peach, or white
- Luster
- vitreous to pearly
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Physical properties
Hardness: 6 on Mohs scale; Color: typically pinkish-orange, peach, or white; Luster: vitreous to pearly; Crystal structure: Monoclinic; Cleavage: two planes at nearly 90 degrees; Specific gravity: 2.55-2.63
Formation & geological history
Commonly formed in igneous rocks such as granite and syenite, as well as in metamorphic rocks like gneiss. It crystallizes from magma or forms through hydrothermal processes in pegmatites.
Uses & applications
Used in the manufacturing of ceramics and glass (as a flux), in abrasive cleansers, and occasionally as a gemstone (sunstone or moonstone varieties).
Geological facts
Orthoclase is one of the most common minerals in the Earth's continental crust. The name comes from the Greek 'orthos' (straight) and 'klasis' (fracture), referring to its two cleavage planes at right angles.
Field identification & locations
Identify in the field by its blocky shape, pinkish-peach color, and pearly luster on cleavage surfaces. Commonly found in mountainous regions with granitic outcrops worldwide.
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Schist
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Metamorphic
Epidote
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metamorphic
Gypsum (variety Selenite or Alabaster)
Calcium sulfate dihydrate (CaSO4·2H2O)
Mineral
Nephrite Jade
Nephrite
Mineral/Rock
Granite
Granite (Phaneritic intrusive igneous rock)
igneous