gemstone
Garnet (Almandine)
Almandine Garnet (Fe3Al2(SiO4)3)
Hardness: 6.5-7.5. Color: Dark deep red to brownish-red. Luster: Vitreous to resinous. Crystal structure: Isometric (cubic). No cleavage. Specific gravity: 3.5-4.3.
- Hardness
- 6
- Color
- Dark deep red to brownish-red
- Luster
- Vitreous to resinous
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Physical properties
Hardness: 6.5-7.5. Color: Dark deep red to brownish-red. Luster: Vitreous to resinous. Crystal structure: Isometric (cubic). No cleavage. Specific gravity: 3.5-4.3.
Formation & geological history
Formed in regional metamorphic rocks such as mica schists and gneisses, and occasionally in igneous rocks. The location provided (Java, Indonesia) has volcanic and metamorphic complexes that can host such stones.
Uses & applications
Primarily used as a gemstone in jewelry (cabochon cut seen here), also used industrially as an abrasive (sandpaper, waterjet cutting) and in watchmaking.
Geological facts
Almandine is the most common variety of garnet. The name is a corruption of Alabanda, a city in Asia Minor where these stones were cut in ancient times. It has been used in jewelry for thousands of years, including in Egyptian burials.
Field identification & locations
Identify by its deep, saturated red color (often appearing black in low light), lack of cleavage, and high hardness. In the field, look for dodecahedral crystals in metamorphic host rocks. Common in Indonesia\'s volcanic belts.
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