igneous
Granitic Pegmatite
Pegmatite containing Quartz, Feldspar, and Muscovite mica
Hardness: 6-7 (quartz/feldspar) and 2-2.5 (mica). Color: White, cream, smoky, and silver. Luster: Vitreous to pearly. Crystal structure: Large, interlocking phaneritic crystals. Cleavage: Perfect in mica, distinct in feldspar.
- Hardness
- 6-7 (quartz/feldspar) and 2-2
- Color
- White, cream, smoky, and silver
- Luster
- Vitreous to pearly
Identified More igneous →
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Physical properties
Hardness: 6-7 (quartz/feldspar) and 2-2.5 (mica). Color: White, cream, smoky, and silver. Luster: Vitreous to pearly. Crystal structure: Large, interlocking phaneritic crystals. Cleavage: Perfect in mica, distinct in feldspar.
Formation & geological history
Formed during the final stage of a magma's crystallization. Highly water-enriched residual fluids allow for the rapid growth of exceptionally large crystals, typically in intrusive dikes or veins.
Uses & applications
Major source of rare elements (lithium, tantalum) and industrial minerals like mica and quartz. Used in high-end construction slabs and as a source for gemstone-quality minerals.
Geological facts
Pegmatites are famous for holding the record for the largest individual crystals ever found on Earth, including spodumene crystals over 40 feet long.
Field identification & locations
Identified by the extremely large grain size compared to surrounding rock. Look for shiny, flaky mica books and glassy quartz masses in mountain belts and shield areas.
