metamorphic
Schist
Mica Schist
Hardness: 3.5-4 on Mohs scale; Color: Silvery-gray, greenish-gray, or brownish due to weathering; Luster: Pearly to sub-metallic; Crystal Structure: Monoclinic (in mineral components); Cleavage: Perfect basal cleavage in mica flakes; Specific Gravity: 2.7-2.8
- Hardness
- 3
- Color
- Silvery-gray, greenish-gray, or brownish due to weathering
- Luster
- Pearly to sub-metallic
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Physical properties
Hardness: 3.5-4 on Mohs scale; Color: Silvery-gray, greenish-gray, or brownish due to weathering; Luster: Pearly to sub-metallic; Crystal Structure: Monoclinic (in mineral components); Cleavage: Perfect basal cleavage in mica flakes; Specific Gravity: 2.7-2.8
Formation & geological history
Formed by the regional metamorphism of shale or mudstone under intermediate to high temperatures and pressures. This creates a foliated texture where platy minerals like mica align in parallel layers.
Uses & applications
Used in construction for decorative stone, paving, and occasionally for roofing. Historically used for flagstones and walls. Some specimens containing garnets or other minerals are sought by collectors.
Geological facts
The word schist is derived from the Greek word 'schizein', meaning 'to split', referring to the ease with which the rock can be layered or split. It is characterized by prominent 'schistosity'.
Field identification & locations
Identify in the field by its distinct layered (foliated) appearance and the presence of visible mica flakes that glitter in the sun. It often feels slightly greasy or soapy if high in chlorite or talc. Found in metamorphic belts worldwide.
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