metamorphic
Almandine Garnet
Almandine (Fe3Al2(SiO4)3)
Hardness: 7-7.5 on the Mohs scale. Color: Dark red to brownish-black. Luster: Vitreous to resinous. Crystal structure: Isometric (dodecahedral). Cleavage: None. Specific gravity: 4.1-4.3.
- Hardness
- 7-7
- Color
- Dark red to brownish-black
- Luster
- Vitreous to resinous
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Physical properties
Hardness: 7-7.5 on the Mohs scale. Color: Dark red to brownish-black. Luster: Vitreous to resinous. Crystal structure: Isometric (dodecahedral). Cleavage: None. Specific gravity: 4.1-4.3.
Formation & geological history
Forms primarily in regional metamorphic rocks such as mica schists and gneisses, where heat and pressure recrystallize sediment-rich minerals. It can also be found in some igneous rocks like granites.
Uses & applications
Used widely as an abrasive (sandpaper, waterjet cutting), in jewelry as a gemstone, and as a common scientific indicator of metamorphic grade.
Geological facts
This specific dodecahedral shape (12-sided) is the classic natural crystal form for garnets. Almandine is the most common member of the garnet group.
Field identification & locations
Identify in the field by its distinct 12-sided crystal habit, high hardness, and density. Commonly found in metamorphic terrains such as the Adirondacks or the Alps.
