metamorphic
Schist (Mica Schist)
Mica Schist
Hardness: 3.5-4; Color: Silvery-gray, metallic; Luster: Pearly to sub-metallic (shimmering); Crystal structure: Monoclinic (foliated); Cleavage: Perfect basal cleavage in mica grains; Specific gravity: 2.7-2.9
- Hardness
- 3
- Color
- Silvery-gray, metallic
- Luster
- Pearly to sub-metallic (shimmering)
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Physical properties
Hardness: 3.5-4; Color: Silvery-gray, metallic; Luster: Pearly to sub-metallic (shimmering); Crystal structure: Monoclinic (foliated); Cleavage: Perfect basal cleavage in mica grains; Specific gravity: 2.7-2.9
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 foliation. Geologically, it can range from 100 million to over 1 billion years old.
Uses & applications
Commonly used as a decorative stone in landscaping, flagstone for walkways, and occasionally as a source of mica for industrial insulation or glitter in cosmetics.
Geological facts
The word 'schist' comes from the Greek word 'schízein', meaning 'to split', referring to how easily the rock can be divided along its layers of mica.
Field identification & locations
Identified by its distinctive 'schistosity' or shimmering, flaky layers that reflect light like glitter. It is frequently found in mountain ranges such as the Appalachians, Alps, and Himalayas. Collectors look for well-defined foliation or embedded garnets.
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