metamorphic
Schist (specifically Mica Schist)
Mica Schist
Hardness: 3.5–4.5 on Mohs scale; Color: Silver, gray, to greenish-black; Luster: Pearly to metallic (sub-metallic); Crystal structure: Foliated (schistosity) with visible grains; Cleavage: Excellent in one direction for individual mica flakes; Specific Gravity: 2.7–3.0.
- Hardness
- 3
- Color
- Silver, gray, to greenish-black
- Luster
- Pearly to metallic (sub-metallic)
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Physical properties
Hardness: 3.5–4.5 on Mohs scale; Color: Silver, gray, to greenish-black; Luster: Pearly to metallic (sub-metallic); Crystal structure: Foliated (schistosity) with visible grains; Cleavage: Excellent in one direction for individual mica flakes; Specific Gravity: 2.7–3.0.
Formation & geological history
Formed through the regional metamorphism of shale or mudstone under medium-grade pressure and temperature conditions. It typically dates back to major orogenic (mountain-building) events throughout Earth's history.
Uses & applications
Used as a decorative stone in architecture, garden walls, and occasionally in the production of filler materials. It is rarely used in heavy construction due to its tendency to split.
Geological facts
Schist is characterized by 'schistosity,' where individual mineral grains (like mica, quartz, or chlorite) are large enough to be seen with the naked eye. The word comes from the Greek 'schizein,' meaning 'to split.'
Field identification & locations
Identify in the field by its distinct 'sparkle' when held in the light and its tendency to flake or split into plates. Commonly found in metamorphic belts such as the Appalachian or Alpine mountain ranges.
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