sedimentary

Grey Banded Agate

Silicon Dioxide (SiO2)

Hardness: 6.5-7 Mohs; Color: Grey, charcoal, and white bands; Luster: Waxy to vitreous; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.58-2.64

Hardness: 6
Color: Grey, charcoal, and white bands
Luster: Waxy to vitreous

Identified July 14, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 Mohs; Color: Grey, charcoal, and white bands; Luster: Waxy to vitreous; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.58-2.64

Formation & geological history

Formed through the deposition of silica from groundwater in the cavities of igneous rocks or sedimentary layers, often over thousands to millions of years.

Uses & applications

Used primarily for ornamental purposes, jewelry (pendants, beads), landscaping, and as a decorative tumbled stone. Sometimes used in industrial mortars and pestles due to its hardness.

Geological facts

Agate is named after the Achates River in Sicily where it was first found. Banded patterns are caused by rhythmic crystallization or changes in the mineral content of the silica-rich fluids during formation.

Field identification & locations

Identify by its waxy luster, translucency, and distinct parallel banding. Commonly found in riverbeds, volcanic regions, and beach gravels globally, with major deposits in Brazil, Uruguay, and the USA.