Mineral

Garnet (likely Almandine or a blend)

Garnet group: X3Y2(SiO4)3, where X can be Ca, Mg, Fe2+, Mn2+ and Y can be Al, Fe3+, Cr3+. Given the dark, somewhat reddish-brown appearance in the image, it's likely Almandine (Fe3Al2(SiO4)3) or a mix with other iron-rich garnets.

Hardness: 6.5-7.5 (Mohs), Color: Dark brown, black, often with greenish or reddish hues; can be opaque to translucent. Luster: Vitreous to resinous. Crystal Structure: Isometric (typically dodecahedral or trapezohedral crystals, though smaller grains might be anhedral). Cleavage: None. Specific Gravity: 3.5-4.3.

Hardness: 6
Color: Dark brown, black, often with greenish or reddish hues
Luster: Vitreous to resinous

Identified August 20, 2025More mineral →

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Physical properties

Formation & geological history

Garnets form under a wide range of geological conditions. They are most commonly found in metamorphic rocks (schists, gneisses, amphibolites) formed by regional or contact metamorphism of aluminum-rich sedimentary rocks or igneous rocks. They can also occur in igneous rocks (e.g., granite, pegmatite, kimberlite) and are resistant to weathering, accumulating in alluvial deposits. Geological age varies widely depending on the formation event, ranging from Precambrian to relatively recent periods.

Uses & applications

Historically used as gemstones and abrasives. In modern industry, garnets are used as an abrasive in sandblasting, waterjet cutting, and sandpaper due to their hardness and durability. Gem-quality garnets are popular in various types of jewelry (rings, necklaces, earrings). Their varied colors make them versatile for different designs.

Geological facts

Garnet is not a single mineral, but a group of silicate minerals with similar crystal structures and physical properties but varying chemical compositions. The name 'garnet' is derived from the Latin 'granatus', meaning 'grain' or 'seed-like', referring to the typical rounded crystals resembling pomegranate seeds. It has been used since the Bronze Age as gemstones and abrasives. Pyrope and Almandine are among the most common garnet species. Special varieties like demantoid garnet are highly prized for their fire.

Field identification & locations

To identify garnet in the field, look for well-formed, often dodecahedral or trapezohedral crystals within metamorphic rocks like schists and gneisses. Their hardness means they scratch glass and are resistant to scratching by a steel knife. The color can range significantly, but dark red to reddish-brown is common. In alluvial deposits, they appear as rounded grains. Commonly found worldwide in numerous metamorphic and some igneous terrains, with major sources including India, Sri Lanka, Brazil, South Africa, and the USA (e.g., Idaho, New York).

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