Igneous
Granitic Pegmatite
Pegmatite (Quartz: SiO2, Feldspar: KAlSi3O8, Mica: KAl2(AlSi3O10)(OH)2)
Hardness: 6-7 (Mohs scale); Color: White, cream, tan with dark inclusions; Luster: Vitreous to pearly; Structure: Phaneritic (very large crystals); Cleavage: Perfect in feldspar and mica constituents.
- Hardness
- 6-7 (Mohs scale)
- Color
- White, cream, tan with dark inclusions
- Luster
- Vitreous to pearly
Identified More igneous →
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Physical properties
Hardness: 6-7 (Mohs scale); Color: White, cream, tan with dark inclusions; Luster: Vitreous to pearly; Structure: Phaneritic (very large crystals); Cleavage: Perfect in feldspar and mica constituents.
Formation & geological history
Formed during the final stage of a magma's crystallization. Highly water-rich magma allows for rapid ion migration, resulting in exceptionally large crystals. Most common in Precambrian and Paleozoic terrains.
Uses & applications
Source of industrial minerals like quartz and feldspar, or rare metals like lithium and niobium. Decorative stone for landscaping or architectural facades.
Geological facts
Pegmatites are known as the 'nature's giant crystal factory.' Individual crystals in some pegmatite deposits have been known to reach over 10 meters in length.
Field identification & locations
Identify by exceptionally large crystal grains (over 1 cm) compared to standard granite. Often found in mountainous regions or shield areas. Collectors look for specific accessory minerals like tourmaline or beryl within the matrix.
