metamorphic
Mica Schist
Mica Schist (primarily Muscovite and Quartz)
Hardness: 3.5 - 4 on Mohs scale; Color: Silvery-gray, metallic, or bronzy; Luster: Pearly to sub-metallic; Crystal Structure: Monoclinic (within the mica flakes); Cleavage: Perfect basal cleavage in individual mica grains; Specific Gravity: 2.7 - 2.8
- Hardness
- 3
- Color
- Silvery-gray, metallic, or bronzy
- Luster
- Pearly to sub-metallic
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Physical properties
Hardness: 3.5 - 4 on Mohs scale; Color: Silvery-gray, metallic, or bronzy; Luster: Pearly to sub-metallic; Crystal Structure: Monoclinic (within the mica flakes); Cleavage: Perfect basal cleavage in individual mica grains; Specific Gravity: 2.7 - 2.8
Formation & geological history
Formed through regional metamorphism of shale or clay-rich sedimentary rocks under intermediate temperatures and pressures. This creates a foliated texture where mica minerals align perpendicularly to the direction of pressure.
Uses & applications
Used historically as a building stone, for decorative flagstones, and in some electrical insulation components. It is also a popular specimen for educational geology kits and hobbyist collectors.
Geological facts
The word 'Schist' is derived from the Greek word 'schistos,' meaning 'split,' referring to the ease with which the rock can be split into thin plates. It often contains 'garnet porphyroblasts,' which are small, round, dark red gemstones embedded within the layers.
Field identification & locations
Identify in the field by its distinct 'shimmer' or 'glitter' when rotated in sunlight and its layered (foliated) texture. It is common in mountain ranges like the Appalachians, Alps, and Himalayas. Collectors should look for flat, scaly surfaces that flake off easily with a fingernail.
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