metamorphic
Garnet in Schist or Pegmatite
Almandine Garnet (Fe3Al2(SiO4)3) in host rock
Hardness of 6.5-7.5 on the Mohs scale, deep red to black color, vitreous to resinous luster, isometric crystal system (often exhibiting dodecahedral or trapezohedral habits), conchoidal fracture with no true cleavage, and specific gravity around 3.5-4.3.
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Physical properties
Hardness of 6.5-7.5 on the Mohs scale, deep red to black color, vitreous to resinous luster, isometric crystal system (often exhibiting dodecahedral or trapezohedral habits), conchoidal fracture with no true cleavage, and specific gravity around 3.5-4.3.
Formation & geological history
Formed under high-temperature and high-pressure metamorphic conditions, typically in regional metamorphic rocks like schists and gneisses, or in igneous pegmatites. Geological age varies depending on the specific metamorphic event, ranging from Precambrian to Cenozoic.
Uses & applications
Used as an abrasive in sandblasting and waterjet cutting, as a semi-precious gemstone in jewelry, and as a prized specimen for mineral collectors.
Geological facts
Garnets have been used since the Bronze Age as gemstones and abrasives. The name comes from the Latin word 'granatus', meaning 'grain', likely referring to the pomegranate fruit due to the similar seed-like appearance of garnet crystals in rock matrix.
Field identification & locations
Can be identified in the field by its distinct crystal habit (rounded polyhedrons protruding from the matrix), dark red-to-black color, and high hardness which resists scratching by a steel knife. Commonly found in metamorphic terrains worldwide, such as schists in New England, USA, or various alpine regions.
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