Rock Identifier
Almandine Garnet (Almandine, Fe3Al2(SiO4)3) — mineral
mineral

Almandine Garnet

Almandine, Fe3Al2(SiO4)3

Hardness of 6.5-7.5 on the Mohs scale, deep red to brownish-red or black color, vitreous to subresinous luster, isometric crystal system commonly forming dodecahedral or trapezohedral habits, conchoidal fracture with no true cleavage, specific gravity of 3.9-4.3.

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Physical properties

Hardness of 6.5-7.5 on the Mohs scale, deep red to brownish-red or black color, vitreous to subresinous luster, isometric crystal system commonly forming dodecahedral or trapezohedral habits, conchoidal fracture with no true cleavage, specific gravity of 3.9-4.3.

Formation & geological history

Forms in metamorphic rocks such as mica schists and gneisses via regional metamorphism of argillaceous sediments, and occasionally in igneous rocks like granitic pegmatites.

Uses & applications

Widely used as an abrasive in waterjet cutting and sandblasting, as well as a gemstone in jewelry.

Geological facts

Garnets have been used as gemstones since the Bronze Age. Almandine is the most common variety of garnet and is often referred to as the carbuncle in ancient literature.

Field identification & locations

Identified by its characteristic dark red color, high hardness, lack of cleavage, and distinct isometric crystal shape (often rounded dodecahedrons). Found worldwide, notably in India, Brazil, Madagascar, and the USA.