sedimentary

Agate

Silicon Dioxide (SiO2)

Hardness: 6.5-7 (Mohs scale); Color: White, cream, and orange-tinted bands; Luster: Waxy to vitreous; Crystal structure: Trigonal (cryptocrystalline); Cleavage: None; Specific gravity: 2.58-2.64

Hardness: 6
Color: White, cream, and orange-tinted bands
Luster: Waxy to vitreous

Identified July 18, 2026More sedimentary →

Explore Agate in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Hardness: 6.5-7 (Mohs scale); Color: White, cream, and orange-tinted bands; Luster: Waxy to vitreous; Crystal structure: Trigonal (cryptocrystalline); Cleavage: None; Specific gravity: 2.58-2.64

Formation & geological history

Formed as a secondary mineral in volcanic rock cavities or sedimentary geodes through the precipitation of silica from groundwater. The characteristic banding represents different stages of mineral deposition over thousands of years.

Uses & applications

Used in ornamental carvings, jewelry (cabochons), and historically for precision tools like laboratory mortars and pestles due to its hardness and chemical resistance.

Geological facts

The name 'Agate' comes from the Achates River in Sicily, where agates were first discovered in ancient times. Agates are actually a variety of chalcedony.

Field identification & locations

Identify in the field by its translucent quality and distinct concentric banding. It is commonly found in riverbeds, gravel pits, and volcanic areas in the Lake Superior region and the Pacific Northwest.