igneous
Pegmatite
Igneous Pegmatite
Hardness: 6-7 on Mohs scale; Color: Varies widely, often white, gray, pink, or black due to constituent minerals; Luster: Vitreous to pearly; Crystal structure: Extremely coarse-grained with crystals often larger than 2.5 cm; Cleavage: Dependent on specific minerals present (e.g., feldspar, quartz);…
- Hardness
- 6-7 on Mohs scale
- Luster
- Vitreous to pearly
Identified More igneous →
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Varies widely, often white, gray, pink, or black due to constituent minerals; Luster: Vitreous to pearly; Crystal structure: Extremely coarse-grained with crystals often larger than 2.5 cm; Cleavage: Dependent on specific minerals present (e.g., feldspar, quartz); Specific gravity: ~2.6 - 2.8.
Formation & geological history
Formed from the water-rich, late-stage crystallization of a magma chamber, often cooling very slowly deep within the Earth's crust to produce exceptionally large crystals.
Uses & applications
Source of rare earth elements, gemstone mining (tourmaline, beryl, topaz), and industrial minerals like quartz, feldspar, and mica.
Geological facts
Pegmatites are famous for hosting the largest individual mineral crystals ever found, sometimes measuring many meters in length.
Field identification & locations
Easily identified by its extremely coarse and variable grain size, often contrasting large light-colored quartz or feldspar with dark minerals like tourmaline or biotite mica. Commonly found in ancient shields and mountain-building belts worldwide.
