igneous
Pegmatite
Igneous Pegmatite (Quartz, Feldspar, Micas)
Hardness typically 6-7 on Mohs scale; mixed white, gray, and dark green/black coloration; vitreous to pearly luster; phaneritic texture with very large, interlocking crystals; specific gravity around 2.5-2.8.
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Physical properties
Hardness typically 6-7 on Mohs scale; mixed white, gray, and dark green/black coloration; vitreous to pearly luster; phaneritic texture with very large, interlocking crystals; specific gravity around 2.5-2.8.
Formation & geological history
Formed from the water-rich, late-stage crystallization of magma deep within the Earth's crust, often taking millions of years to cool, allowing exceptionally large crystals to grow.
Uses & applications
Source of rare-earth elements, industrial minerals like quartz and feldspar, and gemstone mining (tourmaline, beryl, topaz).
Geological facts
Pegmatites are famous for containing some of the largest individual crystals ever found on Earth, sometimes measuring several meters in length.
Field identification & locations
Identified by its extremely coarse-grained texture (crystals significantly larger than surrounding rocks), commonly found associated with large granitic plutons worldwide.
