igneous
Pegmatite containing Muscovite and Quartz
Granitic Pegmatite (SiO2 with KAl2(AlSi3O10)(OH)2)
Hardness: 6-7 (quartz/feldspar) / 2-2.5 (mica); Color: White, pink, silvery-gray; Luster: Vitreous to pearly; Crystal structure: Monoclinic (mica) and Hexagonal (quartz); Cleavage: Perfect basal cleavage in mica flakes.
- Hardness
- 6-7 (quartz/feldspar) / 2-2
- Color
- White, pink, silvery-gray
- Luster
- Vitreous to pearly
Identified More igneous →
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Physical properties
Hardness: 6-7 (quartz/feldspar) / 2-2.5 (mica); Color: White, pink, silvery-gray; Luster: Vitreous to pearly; Crystal structure: Monoclinic (mica) and Hexagonal (quartz); Cleavage: Perfect basal cleavage in mica flakes.
Formation & geological history
Formed during the final stage of a magma's crystallization. Highly fluid, water-rich magma allows for the growth of exceptionally large crystals in intrusive igneous environments, often in dikes or veins.
Uses & applications
Source of industrial mica for electronics and insulation, quartz for glass making, and specimen collecting for geological study. Mica flakes are often used in cosmetics for shimmer.
Geological facts
Pegmatites are famous for containing the largest crystals found on Earth; some muscovite 'books' have been found measuring several meters across.
Field identification & locations
Identified by the extremely coarse grain size where individual mineral crystals are larger than 1 cm. Look for the 'books' of shiny, peeling mica flakes embedded in a white or pink crystalline matrix.
