metamorphic
Garnet in Matrix (likely Almandine Garnet)
Almandine (Fe3Al2(SiO4)3)
Hardness: 6.5-8.5 (Mohs scale); Color: Deep brownish-red to black speckled crystals; Luster: Vitreous to resinous; Crystal structure: Isometric/Dodecahedral; Cleavage: None (conchoidal fracture); Specific Gravity: 3.5-4.3
- Hardness
- 6
- Color
- Deep brownish-red to black speckled crystals
- Luster
- Vitreous to resinous
Identified More metamorphic →
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Physical properties
Hardness: 6.5-8.5 (Mohs scale); Color: Deep brownish-red to black speckled crystals; Luster: Vitreous to resinous; Crystal structure: Isometric/Dodecahedral; Cleavage: None (conchoidal fracture); Specific Gravity: 3.5-4.3
Formation & geological history
Formed during regional metamorphism of clay-rich sedimentary rocks (shale) under high pressure and temperature. These specimens are typically found in mica schists or gneisses. Common in Precambrian and Paleozoic metamorphic belts worldwide.
Uses & applications
Industrial abrasive (waterjet cutting, sandblasting), gemstones for jewelry, and lapidary decorative items like this carved heart.
Geological facts
Garnet is the birthstone for January and was used by ancient Egyptian pharaohs as decorative jewelry. It is one of the few gemstones that is typically not treated or enhanced with heat or radiation.
Field identification & locations
Identify in the field by its distinct deep red color, high hardness, and dodecahedral crystal habit. Often found in schist where the surrounding rock is softer mica. Popular locations include New York (Gore Mountain), Idaho, and India.
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