metamorphic
Muscovite Schist
Mica Schist (KAl2(AlSi3O10)(OH)2 matrix)
Hardness: 2 to 2.5 (individual mica flakes) but specimen is brittle. Color: Silvery-gray, metallic white. Luster: Pearly to sub-metallic. Crystal Structure: Monoclinic (foliated). Cleavage: Perfect basal cleavage in mica components.
- Hardness
- 2 to 2
- Color
- Silvery-gray, metallic white
- Luster
- Pearly to sub-metallic
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Physical properties
Hardness: 2 to 2.5 (individual mica flakes) but specimen is brittle. Color: Silvery-gray, metallic white. Luster: Pearly to sub-metallic. Crystal Structure: Monoclinic (foliated). Cleavage: Perfect basal cleavage in mica components.
Formation & geological history
Formed through the regional metamorphism of shale or mudstone under intermediate to high temperatures and pressures. This creates coarse-grained foliated textures where flaky mica minerals align.
Uses & applications
Used primarily as a source of mica for electrical insulation, filler in plastics or rubber, and occasionally as a decorative or building stone (flagstone). Highly valued by geology students for studying metamorphic grades.
Geological facts
The 'sparkle' in schist comes from the mica reflecting light. Because of its sheet-like crystal structure, mica can be peeled into incredibly thin, heat-resistant transparent layers.
Field identification & locations
Identify in the field by its distinct silvery glitter and flaky, layered (foliated) texture that breaks easily along planes. Commonly found in mountain ranges like the Appalachians or Alps.
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