metamorphic
Mica Schist
Crystalline Schist (often containing Muscovite, Biotite, and Quartz)
Hardness: 3.5-4 Mohs scale; Color: Silvery-gray to black with metallic sheen; Luster: Pearly to sub-metallic; Crystal structure: Monoclinic (within mineral layers); Cleavage: Perfect basal cleavage in mica components; Specific gravity: 2.7-2.8.
- Hardness
- 3
- Color
- Silvery-gray to black with metallic sheen
- Luster
- Pearly to sub-metallic
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Physical properties
Hardness: 3.5-4 Mohs scale; Color: Silvery-gray to black with metallic sheen; Luster: Pearly to sub-metallic; Crystal structure: Monoclinic (within mineral layers); Cleavage: Perfect basal cleavage in mica components; Specific gravity: 2.7-2.8.
Formation & geological history
Formed through the regional metamorphism of clay-rich sedimentary rocks (like shale) under medium to high temperatures and pressure. It represents an intermediate grade of metamorphism between phyllite and gneiss.
Uses & applications
Used primarily in construction for decorative stone, facade cladding, and garden landscaping. High-quality mica extracted from it is used in electrical insulators and cosmetics.
Geological facts
The word 'Schist' is derived from the Greek 'schistos', meaning 'split', referring to the ease with which the rock can be layered or split. It is highly characterized by 'schistosity', the alignment of platy minerals.
Field identification & locations
Identify in the field by its distinct foliation (shimmering layers) and high concentrations of reflective mica flakes. Often found in mountain belts such as the Appalachians, Alps, and Himalayas. Collectors look for garnet inclusions common in this rock.
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