metamorphic
Mica Schist
Mica Schist (primarily Muscovite and Quartz)
Hardness: 3.5-5.5 (Mohs); Color: Silvery-gray, metallic/shiny; Luster: Pearly to Vitreous; Crystal structure: Monoclinic (plates); Cleavage: Perfect basal (flaking); Specific Gravity: 2.8-3.0.
- Hardness
- 3
- Color
- Silvery-gray, metallic/shiny
- Luster
- Pearly to Vitreous
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Physical properties
Hardness: 3.5-5.5 (Mohs); Color: Silvery-gray, metallic/shiny; Luster: Pearly to Vitreous; Crystal structure: Monoclinic (plates); Cleavage: Perfect basal (flaking); Specific Gravity: 2.8-3.0.
Formation & geological history
Formed through regional metamorphism of shale or mudstone under medium-grade pressure and temperature (300-450°C). This process causes platy minerals like mica to align, creating a foliated 'schistose' texture.
Uses & applications
Used occasionally as decorative building stone, flagging, or for landscaping. Muscovite mica specifically is used in electrical insulation and as a glittery additive in makeup and paints.
Geological facts
The word 'schist' is derived from the Greek word 'schizein', meaning 'to split', referring to how easily the rock can be flaked into thin plates due to its foliation.
Field identification & locations
Identify in the field by its distinct 'glittery' appearance and foliated layers that flake off easily with a fingernail or knife. Commonly found in core mountain ranges like the Appalachians or Alps.
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