sedimentary

Banded Agate

Silicon Dioxide (SiO2)

Hardness: 6.5-7 on the Mohs scale. Color: Deep purplish-brown with white/gray bands. Luster: Waxy to vitreous. Crystal structure: Cryptocrystalline. Cleavage: None. Specific gravity: 2.58-2.64.

Hardness: 6
Color: Deep purplish-brown with white/gray bands
Luster: Waxy to vitreous

Identified July 15, 2026More sedimentary →

Explore Banded 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 on the Mohs scale. Color: Deep purplish-brown with white/gray bands. Luster: Waxy to vitreous. Crystal structure: Cryptocrystalline. Cleavage: None. Specific gravity: 2.58-2.64.

Formation & geological history

Formed in volcanic rock cavities or sedimentary veins through the deposition of silica from groundwater. The bands represent different pulses of mineral-rich fluids over thousands of years.

Uses & applications

Commonly used for lapidary work, jewelry (beads, cabochons), tumbled stones for collecting, and ornamental carvings.

Geological facts

The banding in agate is caused by rhythmic crystallization. Some agates, like Lake Superior Agates, are over a billion years old. This specific dark specimen exhibits characteristic waxy luster common in water-worn stones.

Field identification & locations

Look for translucent edges and concentric or parallel banding when held to a light source. Often found on beaches or in riverbeds where volcanic rocks have weathered away. Common in Brazil, India, and the Midwestern USA.