igneous
Granitic Pegmatite
Pegmatitic Granite
Hardness (Mohs): 6-7; Color: White, gray, pink with black and red accents; Luster: Vitreous to dull; Crystal structure: Phaneritic (large crystals); Cleavage: Perfect in feldspars, none in quartz; Specific Gravity: 2.6-2.7
- Color
- White, gray, pink with black and red accents
- Luster
- Vitreous to dull
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Physical properties
Hardness (Mohs): 6-7; Color: White, gray, pink with black and red accents; Luster: Vitreous to dull; Crystal structure: Phaneritic (large crystals); Cleavage: Perfect in feldspars, none in quartz; Specific Gravity: 2.6-2.7
Formation & geological history
Formed during the final stages of a magma's crystallization, where high water content allows for the growth of exceptionally large crystals. These are often found in plutons or as dikes and veins.
Uses & applications
Source of industrial minerals like quartz and feldspar; used in construction, high-end countertops, and as a source for rare earth elements or gemstones.
Geological facts
Pegmatites are famous for holding the largest crystals ever found on Earth, sometimes reaching several meters in length. They often contain rare minerals not found in standard granite.
Field identification & locations
Identify by looking for very large, interlocking crystals of quartz and feldspar. Look for black tourmaline or red garnet inclusions. Common in mountain ranges and ancient continental shields.
