metamorphic
Almandine Garnet in Matrix
Almandine, Fe3Al2(SiO4)3
Hardness: 6.5-7.5. Color: Dark red to brownish-red. Luster: Vitreous to resinous. Crystal structure: Isometric (dodecahedral). Cleavage: None. Specific gravity: 3.5-4.3.
- Hardness
- 6
- Color
- Dark red to brownish-red
- Luster
- Vitreous to resinous
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Physical properties
Hardness: 6.5-7.5. Color: Dark red to brownish-red. Luster: Vitreous to resinous. Crystal structure: Isometric (dodecahedral). Cleavage: None. Specific gravity: 3.5-4.3.
Formation & geological history
Forms primarily in metamorphic rocks like mica schists or gneisses through high-pressure and high-temperature regional metamorphism. Often found in Precambrian units or younger orogenic belts.
Uses & applications
Used as an abrasive in sandblasting and water-jet cutting due to hardness, and widely used as a gemstone in jewelry.
Geological facts
Garnets have been used as gemstones since the Bronze Age. Almandine is the most common member of the garnet group and is the official state gemstone of New York.
Field identification & locations
Identify by its characteristic 12-sided crystal shape (dodecahedron), red-brown color, and lack of cleavage. Often found in schist matrix in locations like the Adirondack Mountains or the Alps.
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