metamorphic
Mica Schist
Mica Schist (contains Muscovite/Biotite, Quartz)
Hardness: 3.5–4 on Mohs scale; Color: Silver, grey, or golden-brown with a glittery appearance; Luster: Pearly to metallic; Structure: Foliated (schistosity) with visible mineral grains; Cleavage: Perfect basal cleavage in individual mica flakes; Specific Gravity: 2.7–2.8.
- Hardness
- 3
- Color
- Silver, grey, or golden-brown with a glittery appearance
- Luster
- Pearly to metallic
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Physical properties
Hardness: 3.5–4 on Mohs scale; Color: Silver, grey, or golden-brown with a glittery appearance; Luster: Pearly to metallic; Structure: Foliated (schistosity) with visible mineral grains; Cleavage: Perfect basal cleavage in individual mica flakes; Specific Gravity: 2.7–2.8.
Formation & geological history
Formed through regional metamorphism of shale or mudstone under intermediate to high temperatures and pressures. This metamorphic process causes mica crystals to grow and align, creating the characteristic layered or 'schistose' texture.
Uses & applications
Used as decorative stone in gardens, as a building material (flagstone), and historically for heat-resistant windows (muscovite). Today, crushed mica is used in electronics, cosmetics for its shimmer, and as a filler in paints and plastics.
Geological facts
The word 'schist' is derived from the Greek word 'schistos', meaning 'split', referring to the stone's tendency to split into thin sheets. If the schist contains many garnets, it is called a Garnet-Mica Schist.
Field identification & locations
Identify in the field by its distinct 'glittery' reflection when held to light and its ability to be flaked off in thin, brittle layers. It is commonly found in mountain ranges such as the Appalachians, Alps, and Himalayas. Collectors should look for balanced foliation and accessory minerals like garnet or staurolite.
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