igneous
Granitic Pegmatite with Muscovite Mica
Pegmatite (containing KAl2(AlSi3O10)(OH)2)
Hardness: 2.5-3 (mica) and 6-6.5 (feldspar); Color: Silvery-white to reflective (mica), salmon pink (potassium feldspar), translucent (quartz); Luster: Pearly to vitreous; Crystal structure: Monoclinic and Hexagonal; Cleavage: Perfect basal.
- Hardness
- 2
- Luster
- Pearly to vitreous
Identified More igneous →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 2.5-3 (mica) and 6-6.5 (feldspar); Color: Silvery-white to reflective (mica), salmon pink (potassium feldspar), translucent (quartz); Luster: Pearly to vitreous; Crystal structure: Monoclinic and Hexagonal; Cleavage: Perfect basal.
Formation & geological history
Formed during the final stages of a magma's crystallization, usually in deep-seated plutonic environments where high water content allows for the growth of exceptionally large crystals.
Uses & applications
Muscovite is used as an electrical insulator, in paints as a pigment extender, and in cosmetics for shimmer. The rock itself is a source of rare minerals and industrial feldspar.
Geological facts
Muscovite was once used as a glass substitute for windows in Russia, leading to the name 'Muscovy glass'. Pegmatites contain the largest crystals ever recorded on Earth.
Field identification & locations
Identify in the field by the exceptionally large grain size (usually >1cm) and the presence of shiny, flat sheets of mica that can be peeled away with a fingernail.
