metamorphic
Schist
Mica Schist
Hardness: 3.5-4; Color: Silvery-gray, white, or greenish; Luster: Pearly to sub-metallic due to mica flakes; Crystal structure: Foliated (schistosity); Cleavage: Perfect basal on mica grains; Specific gravity: 2.7-2.8
- Hardness
- 3
- Color
- Silvery-gray, white, or greenish
- Luster
- Pearly to sub-metallic due to mica flakes
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Physical properties
Hardness: 3.5-4; Color: Silvery-gray, white, or greenish; Luster: Pearly to sub-metallic due to mica flakes; Crystal structure: Foliated (schistosity); Cleavage: Perfect basal on mica grains; Specific gravity: 2.7-2.8
Formation & geological history
Formed from the medium-grade metamorphism of shale or mudstone. Subjected to higher temperatures and pressures than slate or phyllite, allowing individual plate-like mineral grains to grow large enough to be visible to the naked eye.
Uses & applications
Used historically as decorative stone for gardens, building flags, and walling. Some schist is used as a source of graphite or garnet, though it is generally not a major construction material due to its tendency to flake.
Geological facts
Schist is defined by its 'schistosity,' a texture of closely spaced, parallel layers of flaky minerals. It often contains accessory minerals like red almandine garnets, which are highly prized by collectors.
Field identification & locations
Identify by its sparkly, 'glittery' appearance under light and its tendency to split into thin sheets or flakes. Commonly found in mountain ranges such as the Appalachians or the Alps. Look for large, visible flakes of muscovite or biotite mica.
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