mineral

Agate

Chalcedony (cryptocrystalline variety of Quartz, SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 Mohs; Color: Brown, tan, white, and translucent orange (waxy or vitreous luster); Structure: Trigonal/Microcrystalline; Cleavage: None (conchoidal fracture).

Hardness: 6

Identified March 4, 2026More mineral →

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; Color: Brown, tan, white, and translucent orange (waxy or vitreous luster); Structure: Trigonal/Microcrystalline; Cleavage: None (conchoidal fracture).

Formation & geological history

Formed primary in volcanic rock cavities (vesicles) or sedimentary fissures through the deposition of silica-rich groundwater. Over millions of years, multiple layers of chalcedony build up to create the characteristic banding.

Uses & applications

Used extensively in jewelry, ornamental carvings, and lapidary art. Historically used for making hard-wearing tools like mortars and pestles for laboratories.

Geological facts

The 'banding' visible in the specimen is its most iconic feature. Some agates have such fine color variations that they were used as decorative talismans in ancient Egypt and Mesopotamia more than 3,000 years ago.

Field identification & locations

Identify in the field by looking for a waxy luster on fractured surfaces and a weight that feels dense for its size. Common in areas with ancient volcanic activity or riverbeds in the American Midwest (Lake Superior) and Brazil.