igneous
Granatic Pegmatite
Pegmatitic Granite
Hardness: 6-7 (Mohs); Color: Pink (feldspar), White/Gray (quartz), Silver-green (mica); Luster: Vitreous to pearly; Crystal structure: Very large interlocking crystals; Cleavage: Good in feldspar and mica areas.
- Hardness
- 6-7 (Mohs)
- Color
- Pink (feldspar), White/Gray (quartz), Silver-green (mica)
- Luster
- Vitreous to pearly
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Physical properties
Hardness: 6-7 (Mohs); Color: Pink (feldspar), White/Gray (quartz), Silver-green (mica); Luster: Vitreous to pearly; Crystal structure: Very large interlocking crystals; Cleavage: Good in feldspar and mica areas.
Formation & geological history
Formed during the final stage of magma crystallization where high water content allows for the growth of exceptionally large crystals. Typically found in batholiths and mountain-forming regions.
Uses & applications
Used as a source of rare elements (lithium, tantalum), as commercial granite for countertops, and as a source for gemstone-quality minerals like beryl or tourmaline.
Geological facts
Pegmatites are unique because they contain the largest crystals found on Earth; some spodumene crystals in pegmatites have reached lengths of over 40 feet.
Field identification & locations
Identify in the field by the exceptionally large grain size (over 1cm) compared to surrounding rock. Look for the distinct mix of salmon-pink potassium feldspar and glassy quartz.
