metamorphic
Garnet Schist
Almandine Garnet (Fe3Al2(SiO4)3) in Mica Schist
Hardness: 6.5-7.5 (Garnet crystals), Color: Deep red to reddish-brown crystals set in a silvery-grey to black matrix, Luster: Vitreous to sub-vitreous, Crystal Structure: Isometric (dodecahedron), Cleavage: Indistinct, Specific Gravity: 3.5-4.3
- Hardness
- 6
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Physical properties
Hardness: 6.5-7.5 (Garnet crystals), Color: Deep red to reddish-brown crystals set in a silvery-grey to black matrix, Luster: Vitreous to sub-vitreous, Crystal Structure: Isometric (dodecahedron), Cleavage: Indistinct, Specific Gravity: 3.5-4.3
Formation & geological history
Formed through regional metamorphism of shale or clay-rich sedimentary rocks under high temperature and pressure conditions, typically in convergent plate boundaries. Found in metamorphic belts worldwide.
Uses & applications
Garnets are used as industrial abrasives (sandblasting, waterjet cutting), and high-quality specimens are faceted for jewelry. Schist with garnets is popular for educational and collector purposes.
Geological facts
Garnets are index minerals used by geologists to determine the degree of metamorphism a rock has undergone. The Almandine variety is the most common member of the garnet group.
Field identification & locations
Identify in the field by looking for distinct, hard, rounded or dodecahedral red crystals protruding from a flaky, foliated, mica-rich rock. Common in regions like the Adirondacks, New England, and the Alps.
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