metamorphic
Biotite Schist
Biotite Schist (Metamorphic Rock featuring K(Mg,Fe)3AlSi3O10(OH)2)
Hardness: 2.5–4, Color: Dark green, brownish-black to black, Luster: Pearly to sub-metallic on cleavage surfaces, Structure: Foliated with distinct schistosity, Cleavage: Excellent basal cleavage, Specific Gravity: 2.7–3.3
- Hardness
- 2
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Physical properties
Hardness: 2.5–4, Color: Dark green, brownish-black to black, Luster: Pearly to sub-metallic on cleavage surfaces, Structure: Foliated with distinct schistosity, Cleavage: Excellent basal cleavage, Specific Gravity: 2.7–3.3
Formation & geological history
Formed through regional metamorphism of shale, mudstone, or igneous precursors at moderate to high temperatures and pressures within continental collision zones and mountain belts.
Uses & applications
Mainly used for educational sets, geological study, and decorative landscaping stone. Not commonly used in high-durability construction due to high foliation and flaking.
Geological facts
Biotite is a dark mica mineral rich in iron and magnesium. Schistosity allows the rock to split easily into thin sheets or flakes along parallel lines of biotite crystals.
Field identification & locations
Easily identified by its dark, shiny, flaky layers of mica flakes that glisten in light. Commonly found in metamorphic terranes like the Appalachian Mountains, Alps, and Scottish Highlands.
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