metamorphic
Mica Schist with Quartz
Mica Schist (primarily Muscovite or Biotite with Quartz)
Hardness: 3.5-7 (variable). Color: Silvery-gray, brownish-gold, or speckled. Luster: Pearly to metallic (sparkly). Crystal structure: Monoclinic (foliated). Cleavage: Perfect basal in mica flakes. Specific gravity: 2.7-2.9.
- Hardness
- 3
- Color
- Silvery-gray, brownish-gold, or speckled
- Luster
- Pearly to metallic (sparkly)
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Physical properties
Hardness: 3.5-7 (variable). Color: Silvery-gray, brownish-gold, or speckled. Luster: Pearly to metallic (sparkly). Crystal structure: Monoclinic (foliated). Cleavage: Perfect basal in mica flakes. Specific gravity: 2.7-2.9.
Formation & geological history
Formed through the regional metamorphism of shale or clay-rich sedimentary rocks under intermediate temperature and pressure conditions. Large mica crystals align to create a foliated texture known as schistosity.
Uses & applications
Used primarily for its aesthetic sparkle in decorative garden stones, historical building facades, and occasionally as a source of industrial mica for insulation or cosmetics.
Geological facts
The sparkle is caused by the alignment of mica minerals which reflect light simultaneously. It is one of the most common rocks in the continental crust's metamorphic belts.
Field identification & locations
Identify by its 'platy' or 'scaly' texture and high shine. It often splits into thin sheets or flakes if pressed. Commonly found in mountain ranges and eroded riverbeds where ancient metamorphic rock is exposed.
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