igneous
Pegmatite (Graphic Granite / Granite Pegmatite)
Coarse-grained intrusive igneous rock (Felsic)
Hardness: 6-7 on Mohs scale; Color: Pink, white, grey, with dark or black mineral inclusions; Luster: Vitreous to pearly; Crystal structure: Very coarse-grained, individual crystals often larger than 2.5 cm; Cleavage: Varies by constituent minerals (feldspar has good cleavage, quartz has none);…
- Hardness
- 6-7 on Mohs scale
- Color
- Pink, white, grey, with dark or black mineral inclusions
- Luster
- Vitreous to pearly
Identified More igneous →
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Pink, white, grey, with dark or black mineral inclusions; Luster: Vitreous to pearly; Crystal structure: Very coarse-grained, individual crystals often larger than 2.5 cm; Cleavage: Varies by constituent minerals (feldspar has good cleavage, quartz has none); Specific Gravity: 2.5-2.8
Formation & geological history
Formed from the slow crystallization of cooling magma deep within the Earth's crust, particularly enriched in water and incompatible elements during the final stages of magmatic crystallization.
Uses & applications
Source of rare earth elements, industrial minerals (feldspar, quartz, mica), and gemstone-quality crystals (tourmaline, beryl, topaz).
Geological facts
Pegmatites can contain some of the largest known crystals in the world, sometimes reaching several meters in length.
Field identification & locations
Identify by its extremely large, interlocking crystals of pink potassium feldspar, translucent quartz, and dark biotite or tourmaline. Commonly found in continental shields and mountain-building belts.
