(mineralogy) A common feldspar of igneous, plutonic, and metamorphic rocks. Orthoclase is the main feldspar of pegmatite occurrences, where it is most commonly flesh-colored. Orthoclase is used in the ceramic and glass industries and as a decorative gravel.
Chemical composition: Potassium aluminum silicate, <math>KAlSi?_3O_8</math>
Moh's Hardness: 6.0
Specific gravity: 2.6
Color: white, flesh, yellow, brown, occasionally colorless
Cleavage: two good at 90Âº
- Habit: Monoclinic - prismatic. Well developed crystal faces are at 90Âº to each other. Occasional twinned crystals are found. Crystal faces typically look polished, and are not striated.
Etymology: ortho (from Greek orthos, straight, perpendicular) + clase (from Greek klastos, broken, to break).
- Dutch: orthoklaas
- German: Orthoklas
- Spanish: ortoclasa
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