metamorphic
Almandine Garnet in Matrix
Almandine (Fe3Al2(SiO4)3)
Hardness: 6.5-7.5 on Mohs scale; Color: Deep red, brownish-red to black; Luster: Vitreous to resinous; Crystal structure: Isometric (dodecahedral); Cleavage: None (conchoidal fracture); Specific gravity: 4.1-4.3
- Hardness
- 6
- Color
- Deep red, brownish-red to black
- Luster
- Vitreous to resinous
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Physical properties
Hardness: 6.5-7.5 on Mohs scale; Color: Deep red, brownish-red to black; Luster: Vitreous to resinous; Crystal structure: Isometric (dodecahedral); Cleavage: None (conchoidal fracture); Specific gravity: 4.1-4.3
Formation & geological history
Formed during regional metamorphism of clay-rich sedimentary rocks (pelites) such as shale. This specimen likely originates from mica schist or gneiss environments, typically dating from the Precambrian to Cenozoic eras depending on the local orogeny.
Uses & applications
Used primarily as an abrasive (sandpaper, waterjet cutting), in jewelry as a gemstone, and as a popular mineral specimen for collectors.
Geological facts
Almandine is the most common member of the garnet group. In ancient times, it was often referred to as 'Carbuncle'. It is the state mineral of Connecticut and the state gemstone of New York.
Field identification & locations
Identify in the field by its distinct 12-sided crystal shape (dodecahedron), high hardness, and lack of cleavage. Common locations include the Adirondack Mountains (USA), Tyrol (Austria), and various metamorphic belts in India and Brazil.
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