metamorphic
Garnet Schist
Almandine Garnet in Mica Schist (Fe3Al2(SiO4)3)
Hardness: 6.5-7.5 (garnets) vs 2-3 (mica matrix); Color: Deep red/brownish garnets in a silver-grey or tan matrix; Luster: Vitreous to resinous garnets, pearly/metallic matrix; Structure: Foliated schistose texture with porphyroblasts.
- Hardness
- 6
- Color
- Deep red/brownish garnets in a silver-grey or tan matrix
- Luster
- Vitreous to resinous garnets, pearly/metallic matrix
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Physical properties
Hardness: 6.5-7.5 (garnets) vs 2-3 (mica matrix); Color: Deep red/brownish garnets in a silver-grey or tan matrix; Luster: Vitreous to resinous garnets, pearly/metallic matrix; Structure: Foliated schistose texture with porphyroblasts.
Formation & geological history
Formed through regional metamorphism of shale or mudstone under high temperature and pressure. Garnets grow as crystals within the solid rock as minerals recrystallize. Typical of mountain-building events (orogenies).
Uses & applications
Abrasives (industrial garnet), geological study, decorative landscaping, and occasionally jewelry if crystals are high-grade. Primarily a collector's specimen.
Geological facts
Garnets are known as 'index minerals' because they allow geologists to determine the temperature and pressure reached during the rock's formation. They are the birthstone for January.
Field identification & locations
Identify by looking for distinct, dark, rounded dodecahedral crystals (garnets) embedded within a flaky, shimmering mica-rich matrix. Often found in metamorphic belts like the Appalachians or Alps.
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