metamorphic
Almandine Garnet in Matrix
Almandine, Fe3Al2(SiO4)3
Hardness: 6.5-8.5 (garnet crystals), Color: Deep red to brownish-red garnet in a tan or light gray matrix, Luster: Vitreous to resinous, Crystal Structure: Isometric (dodecahedral)
- Hardness
- 6
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Physical properties
Hardness: 6.5-8.5 (garnet crystals), Color: Deep red to brownish-red garnet in a tan or light gray matrix, Luster: Vitreous to resinous, Crystal Structure: Isometric (dodecahedral)
Formation & geological history
Formed during regional metamorphism of clay-rich sedimentary rocks under high temperature and pressure, typically in mica schists or gneisses.
Uses & applications
Primarily used as an industrial abrasive for waterjet cutting and sandblasting; high-quality crystals are used as gemstones and in jewelry.
Geological facts
Almandine is the most common member of the garnet group. It is sometimes called 'Carbuncle' when cut as a cabochon, a term historically used for any red gem.
Field identification & locations
Identify in the field by looking for distinct red, round, or dodecahedral crystals embedded in a lighter-colored, often schistose or granular matrix. Common globally in metamorphic terranes.
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