igneous
Feldspar Pegmatite
Pegmatitic Potassium Feldspar (KAlSi3O8) with Quartz and Mica
Hardness: 6.0-6.5 (Mohs scale), Color: Pinkish-tan to fleshy red, Luster: Vitreous to pearly, Crystal structure: Monoclinic or Triclinic (granitic), Cleavage: Two directions at nearly 90 degrees
- Hardness
- 6
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Physical properties
Hardness: 6.0-6.5 (Mohs scale), Color: Pinkish-tan to fleshy red, Luster: Vitreous to pearly, Crystal structure: Monoclinic or Triclinic (granitic), Cleavage: Two directions at nearly 90 degrees
Formation & geological history
Formed during the final stages of magma crystallization where high water content allows for the growth of exceptionally large crystals. These are commonly found in plutonic igneous intrusions.
Uses & applications
Feldspar is used in the manufacture of glass and ceramics (as a flux), as a filler in paints and plastics, and occasionally as a gemstone (Sunstone or Moonstone) if high quality.
Geological facts
Pegmatites often contain the largest crystals found on Earth, sometimes reaching over 10 meters in length. They are also primary sources for rare elements like lithium, tantalum, and niobium.
Field identification & locations
Identify by the coarse, oversized crystal grains (larger than 1cm) and the characteristic pinkish hue of orthoclase. Commonly found in mountainous regions near granite batholiths.
