Mineral

Garnet (Almandine variety)

Almandine, Fe3Al2(SiO4)3

Hardness: 6.5-7.5 (Mohs scale), Color: Deep red, brownish-red to black, Luster: Vitreous to resinous, Crystal Structure: Isometric (dodecahedral or trapezohedral), Cleavage: None (indistinct), Specific Gravity: 3.5-4.3

Hardness: 6

Identified March 7, 2026More mineral →

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Physical properties

Formation & geological history

Formed through regional metamorphism of clay-rich sedimentary rocks (shales) under high temperature and pressure. Can be found in metamorphic rocks like mica schists or as weathered grains in alluvial deposits. Age varies widely across geological time scales.

Uses & applications

Used in high-end jewelry when gem-quality, as an industrial abrasive (sandpaper and waterjet cutting), and as a birthstone (January).

Geological facts

Garnet crystals often grow as 'porphyroblasts' within metamorphic rocks, meaning they grow larger than the surrounding mineral grains. Red garnets were the most popular gemstones in the Late Antique Roman world.

Field identification & locations

Identify in the field by their characteristic 'soccer ball' shape (dodecahedron), high hardness, and resistance to weathering. Commonly found in schist outcrops in locations like the Adirondacks (USA) or across various mountain ranges worldwide. These specimens appear to be weathered or partially encased in mica schist.