metamorphic
Schist
Mica Schist (primarily composed of quartz, feldspar, and mica)
Hardness: 3.5-4 on Mohs scale; Color: Silvery-gray to brownish-red due to iron oxidation; Luster: Pearly to sub-metallic; Crystal Structure: Foliated with large, visible mineral grains; Cleavage: Excellent basal cleavage in mica components; Specific Gravity: 2.5-2.9
- Hardness
- 3
- Color
- Silvery-gray to brownish-red due to iron oxidation
- Luster
- Pearly to sub-metallic
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Physical properties
Hardness: 3.5-4 on Mohs scale; Color: Silvery-gray to brownish-red due to iron oxidation; Luster: Pearly to sub-metallic; Crystal Structure: Foliated with large, visible mineral grains; Cleavage: Excellent basal cleavage in mica components; Specific Gravity: 2.5-2.9
Formation & geological history
Formed through the regional metamorphism of shale or mudstone under intermediate to high pressure and temperature. This process aligns mineral grains into parallel layers called schistosity. Most date back to major mountain-building events (Orogenies).
Uses & applications
Used primarily in construction for flagstone, decorative garden walls, and interior flooring. Historically used as a building stone for houses and fences in regions where it is abundant.
Geological facts
The term 'Schist' is derived from the Greek word 'schistos', meaning 'split', referring to the ease with which the rock can be cleaved into thin plates. It represents a medium grade of metamorphism between phyllite and gneiss.
Field identification & locations
Identify in the field by its distinct 'shimmery' or glittery appearance caused by mica flakes and its prominent foliation (layering). It is commonly found in metamorphic terranes like the Appalachian Mountains, the Alps, and the Scottish Highlands.
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