sedimentary

Banded Agate (Quartz)

Agate (Silicon Dioxide, SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 on Mohs scale; Color: Reddish-brown, white, and tan bands; Luster: Waxy to vitreous; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture).

Hardness: 6
Color: Reddish-brown, white, and tan bands
Luster: Waxy to vitreous

Identified July 4, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 on Mohs scale; Color: Reddish-brown, white, and tan bands; Luster: Waxy to vitreous; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture).

Formation & geological history

Formed in cavities of volcanic or sedimentary rocks where silica-rich groundwater deposits layers of chalcedony over time. These rounded specimens are often further smoothed by water erosion in rivers or along coastlines.

Uses & applications

Commonly used for ornamental carvings, jewelry (cabochons), tumbled stones for collecting, and industrial mortars and pestles due to its hardness.

Geological facts

Agate is named after the Achates River in Sicily where it was first discovered. The banding is caused by rhythmic crystallization as fluid chemistry changes during formation.

Field identification & locations

Identify in the field by its waxy texture, translucency when held to light, and characteristic concentric or parallel banding. Commonly found in riverbeds, glacial till, and coastal areas.