metamorphic
Almandine Garnet
Iron aluminum silicate (Fe3Al2(SiO4)3)
Hardness: 6.5-7.5. Color: Deep red, purplish-red to blackish-red. Luster: Vitreous to resinous. Crystal Structure: Isometric (dodecahedron). Cleavage: None. Specific Gravity: 3.5-4.3.
- Hardness
- 6
- Color
- Deep red, purplish-red to blackish-red
- Luster
- Vitreous to resinous
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Physical properties
Hardness: 6.5-7.5. Color: Deep red, purplish-red to blackish-red. Luster: Vitreous to resinous. Crystal Structure: Isometric (dodecahedron). Cleavage: None. Specific Gravity: 3.5-4.3.
Formation & geological history
Formed under high-pressure and high-temperature metamorphic conditions in regional metamorphic rocks such as mica schists and gneisses, or as an accessory mineral in some igneous rocks.
Uses & applications
Commonly used as an abrasive in sandblasting and waterjet cutting; high-quality transparent specimens are used as gemstones in jewelry.
Geological facts
Almandine is the most common species of the garnet group. Garnets have been used as gemstones for thousands of years, notably by ancient Egyptians and Romans.
Field identification & locations
Identify in the field by its distinct dodecahedral crystal habit, deep red color, and high hardness. Commonly found in metamorphic terrains such as the Adirondack Mountains (NY), India, and Brazil.
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