sedimentary

Banded Agate

Cryptocrystalline variety of Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 Mohs; Color: Brown, tan, white, and translucent gray; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline); Cleavage: None; Fracture: Conchoidal.

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

Identified July 2, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 Mohs; Color: Brown, tan, white, and translucent gray; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline); Cleavage: None; Fracture: Conchoidal.

Formation & geological history

Formed in cavities (vesicles) of volcanic rocks or sedimentary deposits where silica-rich groundwater precipitates layers of microscopic quartz over long periods.

Uses & applications

Commonly used in jewelry as cabochons, for ornamental carvings, polished as pocket stones, and historically for burnishing tools and mortars/pestles.

Geological facts

The banding in agate is caused by the rhythmic precipitation of silica. Every line represents a different pulse of mineral-rich water entering the hollow cavity.

Field identification & locations

Identified by its waxy luster and distinctive concentric or parallel banding. Look for translucent areas when held to a light source. Commonly found in riverbeds and gravel pits.