metamorphic
Almandine Garnet in Schist
Almandine Garnet (Fe3Al2(SiO4)3) in Mica Schist
Hardness: 6.5-7.5 (garnet), 2-3 (schist matrix); Color: Dark reddish-brown crystals in a silver-grey or tan matrix; Luster: Vitreous to resinous; Crystal structure: Isometric (dodecahedron); Specific gravity: 3.5-4.3.
- Hardness
- 6
- Color
- Dark reddish-brown crystals in a silver-grey or tan matrix
- Luster
- Vitreous to resinous
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Physical properties
Hardness: 6.5-7.5 (garnet), 2-3 (schist matrix); Color: Dark reddish-brown crystals in a silver-grey or tan matrix; Luster: Vitreous to resinous; Crystal structure: Isometric (dodecahedron); Specific gravity: 3.5-4.3.
Formation & geological history
Formed through regional metamorphism of clay-rich sedimentary rocks (pelites) under high pressure and temperature. Most specimens date from the Proterozoic to Paleozoic eras.
Uses & applications
Abrasives (sandpaper, waterjet cutting), gemstones in jewelry, and geological indicators of metamorphic grade.
Geological facts
Garnets are known as 'index minerals,' helping geologists determine the temperature and pressure conditions the rock experienced during its formation deep within the Earth's crust.
Field identification & locations
Identify in the field by the distinct 12-sided 'soccer ball' shape of the reddish crystals protruding from a flaky, micaceous matrix. Common in the Appalachian Mountains, Alps, and Brazil.
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