metamorphic
Almandine Garnet in Matrix
Almandine Garnet (Fe3Al2(SiO4)3) in Schist/Quartz Matrix
Hardness: 6.5 - 7.5; Color: Deep red, reddish-brown to black; Luster: Vitreous to resinous; Crystal structure: Isometric (dodecahedron); No cleavage; Specific gravity: 4.1 - 4.3.
- Hardness
- 6
- Color
- Deep red, reddish-brown to black
- Luster
- Vitreous to resinous
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Physical properties
Hardness: 6.5 - 7.5; Color: Deep red, reddish-brown to black; Luster: Vitreous to resinous; Crystal structure: Isometric (dodecahedron); No cleavage; Specific gravity: 4.1 - 4.3.
Formation & geological history
Formed during regional metamorphism of clay-rich sedimentary rocks (pelites) under high pressure and temperature conditions, typically within the garnet zone of metamorphic facies.
Uses & applications
Used primarily as an abrasive (sandpaper, waterjet cutting) and as a semi-precious gemstone in jewelry or as high-quality mineral specimens for collectors.
Geological facts
Almandine is the most common member of the garnet group. It is the birthstone for January and has been used for beads and jewelry since the Roman Empire.
Field identification & locations
Identify by its distinct 12-sided crystal shape (dodecahedron), dark red color, and high hardness. Commonly found in metamorphic terrains like the Adirondack Mountains (USA), India, and Brazil.
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