metamorphic
Garnet in Matrix
Almandine or Spessartine Garnet in Quartz/Schist Matrix (X3Al2(SiO4)3)
Hardness: 6.5-7.5 (garnet) vs 3-5 (matrix). Color: deep reddish-brown to orange crystals in a white/grey host. Luster: Vitreous to resinous. Crystal structure: Isometric (dodecahedral crystals).
- Hardness
- 6
- Color
- deep reddish-brown to orange crystals in a white/grey host
- Luster
- Vitreous to resinous
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Physical properties
Hardness: 6.5-7.5 (garnet) vs 3-5 (matrix). Color: deep reddish-brown to orange crystals in a white/grey host. Luster: Vitreous to resinous. Crystal structure: Isometric (dodecahedral crystals).
Formation & geological history
Formed under high pressure and temperature during regional metamorphism of clay-rich sedimentary rocks or in pegmatites. Common in metamorphic belts like the Appalachians or Alps.
Uses & applications
Garnets are used as industrial abrasives (sandpaper, waterjet cutting), gemstones in jewelry, and as indicators for metamorphic grade in geology.
Geological facts
Garnet is the birthstone for January. The name comes from the Latin 'granatus' meaning grain or seed, similar to the seeds of a pomegranate.
Field identification & locations
Identify by the characteristic 'soccer-ball' crystal shape (dodecahedron) and high hardness compared to the surrounding matrix. Often found in areas with schist or gneiss bedrock.
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