mineral

Almandine Garnet

Almandine (Fe3Al2(SiO4)3)

Hardness: 6.5–7.5 Mohs; Color: Deep red, reddish-brown to black; Luster: Vitreous to resinous; Crystal structure: Isometric (dodecahedral); Cleavage: None; Specific gravity: 4.1–4.3

Hardness: 6
Color: Deep red, reddish-brown to black
Luster: Vitreous to resinous

Identified April 27, 2026More mineral →

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Physical properties

Hardness: 6.5–7.5 Mohs; Color: Deep red, reddish-brown to black; Luster: Vitreous to resinous; Crystal structure: Isometric (dodecahedral); Cleavage: None; Specific gravity: 4.1–4.3

Formation & geological history

Formed in regional metamorphic environments, specifically in mica schists and gneisses where high pressure and temperature cause the recrystallization of clay minerals. They can be found in rocks from the Proterozoic to more recent geological eras.

Uses & applications

Abrasives (sandblasting, waterjet cutting), gemstones in jewelry, and geological indicators for metamorphic grade. Rough specimens are popular for mineral collecting.

Geological facts

Garnets are the birthstone for January. Almandine is the most common member of the garnet group. When translucent, it is often called 'Carbuncle' in historic texts. Some examples from Idaho exhibit an 'asterism' or star effect.

Field identification & locations

Identify by its characteristic dodecahedral shape (though often water-worn like this sample), high density, and deep red tint when held to light. Common in metamorphic belts like the Adirondacks, Alps, and Himalayas. Check stream beds near metamorphic rock outcrops.