mineral

Rough Garnet (Almandine)

Almandine Garnet (Fe3Al2(SiO4)3)

Hardness: 6.5–7.5 on Mohs scale; Color: Reddish-brown, deep red, or brownish-purple; Luster: Vitreous to resinous; Crystal structure: Isometric (often dodecahedral); Cleavage: Indistinct; Specific gravity: 3.5–4.3

Hardness: 6
Color: Reddish-brown, deep red, or brownish-purple
Luster: Vitreous to resinous

Identified March 8, 2026More mineral →

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Physical properties

Formation & geological history

Formed through regional metamorphism of clay-rich sedimentary rocks (like shale or schist). Heat and pressure during tectonic events recrystallize minerals into garnet. Often Paleozoic or older depending on the local terrane.

Uses & applications

Commonly used as an industrial abrasive (sandblasting, waterjet cutting), in sandpaper, and as a gemstone when gem-grade (transparent/translucent). Also a popular collector specimen in its rough state.

Geological facts

Garnet has been used as a gemstone since the Bronze Age. Almandine is the most common variety of the garnet group and is the official state mineral of Connecticut and the state gemstone of New York.

Field identification & locations

Identify by its characteristic roundish 'soccer ball' shape (crystal form), high density (it feels heavy for its size), and deep red hue when held to light. Common in metamorphic belts; frequently found in creek beds as 'river garnets'.

Other mineral specimens

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Sandstone (with potential mineral staining/concretions)

Arenite (SiO2 based)

sedimentary

Epidote

Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)

metamorphic

Nephrite Jade

Nephrite

Mineral/Rock

Banded Gneiss (River Rock/Pebble)

Gneiss (specifically a banded variety often found as a river rock)

Metamorphic Rock

Green Apatite on Albite

Fluorapatite [Ca5(PO4)3F] on Albite [Na(AlSi3O8)]

mineral

Epidote

Epidote - Ca2(Al2,Fe3+)3(SiO4)3(OH)

mineral