metamorphic
Garnet Schist
Almandine-Garnet Schist
Hardness: 6.5-7.5 (garnets) 2-3 (mica/matrix). Color: Dark reddish-brown crystals in a silver-grey or black matrix. Luster: Vitreous to resinous crystals, pearly matrix. Crystal system: Isometric (garnets).
- Hardness
- 6
- Color
- Dark reddish-brown crystals in a silver-grey or black matrix
- Luster
- Vitreous to resinous crystals, pearly matrix
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Physical properties
Hardness: 6.5-7.5 (garnets) 2-3 (mica/matrix). Color: Dark reddish-brown crystals in a silver-grey or black matrix. Luster: Vitreous to resinous crystals, pearly matrix. Crystal system: Isometric (garnets).
Formation & geological history
Formed under regional metamorphism of clay-rich sedimentary rocks (pelites) such as shale. High pressure and temperature causes recrystallization of minerals like muscovite, biotite, and garnet.
Uses & applications
Industrial abrasive (garnet sand), minor gemstone use for high-quality crystals, and common geological teaching specimens.
Geological facts
Garnet-bearing schists are index rocks for high-grade metamorphic zones. The presence of large garnet crystals indicates the rock reached substantial depths during mountain building.
Field identification & locations
Identify by looking for hard, isometric (12-sided) dark red crystals embedded in a foliated, shiny, mica-rich rock. Found in mountain belts like the Appalachians, Alps, or Himalayas.
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