mineral

Banded agate (likely jasper/chalcedony nodule)

Microcrystalline quartz, SiO₂ (chalcedony with iron-oxide inclusions)

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; cream, tan, gray, and rusty-brown banding; waxy to glassy luster; cryptocrystalline, massive structure with no visible cleavage. The rounded, polished-looking surface may be naturally weathered or tumbled.

Identified August 23, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities in volcanic rock, depositing successive layers of chalcedony and quartz; iron oxides create the brown-red coloration. Individual nodules can range from young to millions of years old depending on the host rock.

Uses & applications

Used for cabochons, beads, carvings, tumbling, and small ornamental objects; attractive specimens have modest jewelry and collector value.

Geological facts

Agate is a variety of chalcedony rather than a separate mineral species. Its internal banding records changing chemistry and conditions during cavity filling.

Field identification & locations

Identify by testing for hardness near quartz, observing curved/concentric bands, and checking that it does not fizz in dilute acid. Common in volcanic terrains worldwide, including Brazil, Uruguay, Mexico, India, and the western United States.