metamorphic
Garnet Schist
Almandine Garnet Schist (Fe3Al2(SiO4)3 in Schistose matrix)
Hardness: 6.5-7.5 (garnets) vs 2-3 (mica matrix); Color: Reddish-brown crystals in gray/silver/tan matrix; Luster: Vitreous to resinous crystals; Crystal structure: Dodecahedral or trapezohedral garnets; Foliated texture.
- Hardness
- 6
- Color
- Reddish-brown crystals in gray/silver/tan matrix
- Luster
- Vitreous to resinous crystals
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Physical properties
Hardness: 6.5-7.5 (garnets) vs 2-3 (mica matrix); Color: Reddish-brown crystals in gray/silver/tan matrix; Luster: Vitreous to resinous crystals; Crystal structure: Dodecahedral or trapezohedral garnets; Foliated texture.
Formation & geological history
Formed through regional metamorphism of clay-rich sedimentary rocks (pelites) under high pressure and temperature during mountain-building events. Typically Proterozoic to Phanerozoic ages.
Uses & applications
Industrial abrasives (garnet paper, waterjet cutting), gemstones if transparent, and educational/collector specimens.
Geological facts
Garnets are index minerals used by geologists to determine the degree of metamorphism (metamorphic grade) that a rock has undergone.
Field identification & locations
Identify by noticing hard, rounded, reddish crystals protruding from a flaky, foliated, or micaceous matrix. Common in metamorphic belts like the Appalachians, Alps, and Himalayas.
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