mineral

Tumbled brown agate

Chalcedony (microcrystalline quartz), SiO₂, with iron-oxide coloration

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; brown to reddish-brown, waxy-to-glassy luster, cryptocrystalline structure, no visible cleavage, and conchoidal fracture. The pale curved banding is characteristic of agate.

Identified September 5, 2026More mineral →

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Physical properties

Hardness 6.5–7 Mohs; brown to reddish-brown, waxy-to-glassy luster, cryptocrystalline structure, no visible cleavage, and conchoidal fracture. The pale curved banding is characteristic of agate.

Formation & geological history

Forms when silica-rich groundwater fills cavities in volcanic rocks, depositing successive layers of chalcedony; individual deposits range from Paleozoic to Cenozoic age. This specimen has been cut or naturally rounded and polished into a tumbled stone.

Uses & applications

Used for cabochons, beads, carvings, ornaments, and lapidary collections; durable agate is also used for small industrial tools and decorative objects.

Geological facts

Agate is a banded variety of chalcedony, and its patterns develop from changing chemistry, impurities, and fluid conditions during cavity filling.

Field identification & locations

Identify it by its fine banding, translucent edges, waxy surface, and lack of cleavage; it commonly occurs in basaltic volcanic regions, including Brazil, Uruguay, Mexico, India, and the western United States.