igneous
Pegmatite (Granitic Pegmatite with Quartz and Feldspar)
Intrusive Igneous Rock (Granitic Pegmatite)
Hardness: 6-7 on Mohs scale. Color: Off-white, pale pink, clear to smoky grey quartz pockets, with dark mica/tourmaline spots. Luster: Vitreous to pearly on feldspar faces. Crystal Structure: Coarse-grained phaneritic/pegmatitic, featuring interlocking crystals of quartz, feldspar, and mica.…
- Hardness
- 6-7 on Mohs scale
- Luster
- Vitreous to pearly on feldspar faces
Identified More igneous →
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Physical properties
Hardness: 6-7 on Mohs scale. Color: Off-white, pale pink, clear to smoky grey quartz pockets, with dark mica/tourmaline spots. Luster: Vitreous to pearly on feldspar faces. Crystal Structure: Coarse-grained phaneritic/pegmatitic, featuring interlocking crystals of quartz, feldspar, and mica. Specific Gravity: ~2.6 - 2.7.
Formation & geological history
Formed during the final stages of a magma body's crystallization, where water-rich fluid residual magma allows exceptionally large crystals to grow rapidly. Found in plutonic environments worldwide, often within continental crusts.
Uses & applications
Major source of industrial feldspar, quartz, and mica. Pegmatites are also the primary economic source for rare metals (lithium, tantalum, beryllium) and gem minerals (beryl, tourmaline, topaz, aquamarine).
Geological facts
Pegmatites can produce some of the largest crystals on Earth, sometimes reaching several meters in length! Small cavity pockets inside pegmatites, like the one visible in this specimen, often contain gem-quality smoky quartz or topaz crystals.
Field identification & locations
Identified by its extremely coarse grain size (crystals larger than 1 cm) dominated by quartz and feldspar, often with small pockets or vugs. Common in granitic shield areas, metamorphic terranes, and ancient mountain belts.
