mineral

Banded Agate (Gray Agate)

Silicon Dioxide (SiO2) - Variety of Chalcedony

Hardness: 6.5-7 Mohs; Color: Gray, black, white concentric bands; Luster: Vitreous to waxy; Crystal Structure: Trigonal/Microcrystalline; Cleavage: None; Specific Gravity: 2.58-2.64

Hardness: 6
Color: Gray, black, white concentric bands
Luster: Vitreous to waxy

Identified June 3, 2026More mineral →

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Physical properties

Hardness: 6.5-7 Mohs; Color: Gray, black, white concentric bands; Luster: Vitreous to waxy; Crystal Structure: Trigonal/Microcrystalline; Cleavage: None; Specific Gravity: 2.58-2.64

Formation & geological history

Formed through the deposition of silica from groundwater in the cavities (vesicles) of igneous rocks, particularly basaltic lava flows. The bands are formed by repeated layers of mineral deposition over thousands of years.

Uses & applications

Primarily used for lapidary arts, jewelry (cabochons), carvings, and as a decorative or metaphysical stone.

Geological facts

The banding in agate is caused by changes in the chemical composition of the silica-rich fluids during formation. This specific specimen has been carved and polished into a crescent moon shape.

Field identification & locations

Identify in the field by its waxy luster, conchoidal fracture, and characteristic banding. Often found in riverbeds or volcanic regions like Brazil, Botswana, or India.

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Sandstone (with potential mineral staining/concretions)

Arenite (SiO2 based)

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Nephrite Jade

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Mineral/Rock

Banded Gneiss (River Rock/Pebble)

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

Metamorphic Rock

Biotite Schist

Biotite-rich Schist [K(Mg,Fe)3AlSi3O10(F,OH)2]

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