metamorphic
Garnet Schist or Garnet-bearing Quartzite
Metamorphic rock containing Almandine Garnet (Fe3Al2(SiO4)3) and Quartz (SiO2)
Hardness: 6.5-7.5 (garnets), 7 (quartz); Color: Tan to grey matrix with reddish-brown inclusions; Luster: Vitreous to greasy; Structure: Granoblastic or foliated; Cleavage: None (conchoidal fracture on quartz).
- Hardness
- 6
- Color
- Tan to grey matrix with reddish-brown inclusions
- Luster
- Vitreous to greasy
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Physical properties
Hardness: 6.5-7.5 (garnets), 7 (quartz); Color: Tan to grey matrix with reddish-brown inclusions; Luster: Vitreous to greasy; Structure: Granoblastic or foliated; Cleavage: None (conchoidal fracture on quartz).
Formation & geological history
Formed through the regional metamorphism of clay-rich sedimentary rocks (pelites) or sandstones under high pressure and temperature conditions deep within the Earth's crust.
Uses & applications
Larger garnets are used as gemstones or abrasives. The rock itself is primarily a collector's specimen or used for geological study. In high-grade forms, it can be used for decorative stone.
Geological facts
Garnets are index minerals, meaning their presence allows geologists to determine the specific temperature and pressure a rock experienced during its formation millions of years ago.
Field identification & locations
Identify by looking for small, rounded, reddish-to-purple 'seeds' (garnets) embedded within a harder, lighter-colored crystalline matrix. Commonly found in metamorphic terrains like the Appalachian or Himalayan mountains.
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