metamorphic
Biotite Schist
Metamorphic Rock (Schist with biotite and quartz-feldspar matrix)
Hardness: 3-4 (biotite), 7 (quartz); Color: Dark brown, black, and grey with silvery sheen; Luster: Pearly to submetallic on cleavage planes; Crystal structure: Foliated, platy texture with visible mica flakes; Specific Gravity: 2.7-3.0
- Hardness
- 3-4 (biotite), 7 (quartz)
- Color
- Dark brown, black, and grey with silvery sheen
- Luster
- Pearly to submetallic on cleavage planes
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Physical properties
Hardness: 3-4 (biotite), 7 (quartz); Color: Dark brown, black, and grey with silvery sheen; Luster: Pearly to submetallic on cleavage planes; Crystal structure: Foliated, platy texture with visible mica flakes; Specific Gravity: 2.7-3.0
Formation & geological history
Formed through regional metamorphism of argillaceous sedimentary rocks like shale or mudstone under high temperature and pressure conditions, typically over hundreds of millions of years.
Uses & applications
Primarily used as a decorative stone, in landscaping, or as educational/study specimens for geology.
Geological facts
Schist is characterized by its strong foliation, meaning the mineral grains are neatly aligned in parallel bands, making the rock prone to splitting along these planes (schistosity).
Field identification & locations
Easily identified by its distinctly sparkling, flaky mica surface and prominent foliation. Found globally in ancient mountain belts and shield areas. Common field identification involves checking for visible platy mineral flakes and parallel alignment.
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