mineral

Banded Agate / Chalcedony

Silicon Dioxide (SiO2) with trace impurities

Hardness: 6.5-7 on Mohs scale. Color: Brown, tan, and white banding. Luster: Waxy to vitreous. Structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific Gravity: 2.58–2.64.

Hardness: 6
Color: Brown, tan, and white banding
Luster: Waxy to vitreous

Identified March 5, 2026More mineral →

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Physical properties

Hardness: 6.5-7 on Mohs scale. Color: Brown, tan, and white banding. Luster: Waxy to vitreous. Structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific Gravity: 2.58–2.64.

Formation & geological history

Formed in cavities (vesicles) of volcanic rocks or sedimentary environments through the deposition of silica-rich groundwater. Agates occur in rocks ranging from Precambrian to Cenozoic age.

Uses & applications

Used primarily for jewelry (cabochons), lapidary art, collection, and precision instruments like pendulum pivots and mortars/pestles due to its hardness.

Geological facts

Agate is a variety of chalcedony distinguished by its distinctive banding. It was named by the Greek philosopher Theophrastus after the Achates River in Sicily where it was first discovered.

Field identification & locations

Identify in the field by its waxy luster, smooth conchoidal fracture, and characteristic concentric or parallel banding when viewed under light. Commonly found in gravel beds or volcanic regions.

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