igneous
Pegmatite (Granitic)
Granitic Pegmatite
Hardness: 6-7 (Mohs); Color: Pink (Feldspar), Black (Biotite/Tourmaline), Gray (Quartz); Luster: Vitreous to pearly; Crystal structure: Coarse-grained phaneritic; Specific gravity: 2.6-2.7
- Hardness
- 6-7 (Mohs)
- Color
- Pink (Feldspar), Black (Biotite/Tourmaline), Gray (Quartz)
- Luster
- Vitreous to pearly
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Physical properties
Hardness: 6-7 (Mohs); Color: Pink (Feldspar), Black (Biotite/Tourmaline), Gray (Quartz); Luster: Vitreous to pearly; Crystal structure: Coarse-grained phaneritic; Specific gravity: 2.6-2.7
Formation & geological history
Formed during the final stages of a magma's crystallization, usually in water-rich environments that allow for the growth of exceptionally large crystals. They are commonly associated with large batholiths.
Uses & applications
Source of lithium, beryllium, and rare earth elements; used for high-quality industrial minerals like feldspar and mica; also used for gemstones like aquamarine or tourmaline.
Geological facts
Pegmatites are famous for containing the largest crystals ever found on Earth, with some individual feldspar crystals reaching over 10 meters in length.
Field identification & locations
Identify by the extremely large grain size compared to surrounding grantic rocks. Commonly found in mountain belts and precambrian shield areas. Key for collectors looking for rare minerals and gems.
