metamorphic
Schist
Mica Schist
Hardness: 3.5-4 Mohs (mica components) to 7 (quartz components); Color: silvery-gray, green, or brown; Luster: Pearly to sub-metallic (shimmery); Crystal Structure: Foliated (schistosity); Cleavage: Perfect in one direction along mica flakes; Specific Gravity: 2.7-2.8
- Hardness
- 3
- Color
- silvery-gray, green, or brown
- Luster
- Pearly to sub-metallic (shimmery)
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Physical properties
Hardness: 3.5-4 Mohs (mica components) to 7 (quartz components); Color: silvery-gray, green, or brown; Luster: Pearly to sub-metallic (shimmery); Crystal Structure: Foliated (schistosity); Cleavage: Perfect in one direction along mica flakes; Specific Gravity: 2.7-2.8
Formation & geological history
Formed through the regional metamorphism of shale or mudstone at medium grades of temperature and pressure. It often dates back to Paleozoic or Proterozoic mountain-building events (orogenies).
Uses & applications
Used as dimension stone for landscaping, decorative garden walls, flagstones, and occasionally for interior surfaces. It lacks the strength for heavy structural construction but is valued for its aesthetic 'glitter'.
Geological facts
The word 'schist' comes from the Greek 'schistos', meaning 'split'. It is characterized by 'schistosity', where the mica grains have grown large enough to be seen with the naked eye and are aligned in parallel layers.
Field identification & locations
Identify in the field by its distinct 'platiness' and its tendency to glitter or sparkle in the sunlight due to alignment of mica flakes. It is commonly found in the Appalachian Mountains and other ancient mountain belts.
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