mineral

Agate (Banded Chalcedony)

Cryptocrystalline Silica (SiO2)

Hardness: 6.5-7 (Mohs scale), Color: tan, white, and translucent brown bands, Luster: waxy to vitreous, Crystal structure: trigonal (microscopic), Cleavage: none, Specific gravity: 2.58-2.64

Hardness: 6

Identified June 11, 2026More mineral →

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Physical properties

Hardness: 6.5-7 (Mohs scale), Color: tan, white, and translucent brown bands, Luster: waxy to vitreous, Crystal structure: trigonal (microscopic), Cleavage: none, Specific gravity: 2.58-2.64

Formation & geological history

Formed in cavities of volcanic or sedimentary rocks where silica-rich groundwater deposits layers of chalcedony over thousands of years. This specimen shows a characteristic geode-like void or druse starting to form.

Uses & applications

Used extensively for lapidary arts, jewelry (beads and cabochons), burnishing tools, and as a popular collector specimen.

Geological facts

Agate is named after the Achates River in Sicily where it was first discovered. The banding transitions represent different pulses of mineral-rich fluids entering a rock cavity.

Field identification & locations

Identified by its waxy luster, translucency when held to light, and distinct concentric or parallel banding. Commonly found in riverbeds, glacial deposits, and volcanic regions.

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Sandstone (with potential mineral staining/concretions)

Arenite (SiO2 based)

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Epidote

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Nephrite Jade

Nephrite

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]

metamorphic