mineral

Brown chalcedony (likely carnelian/agate)

Microcrystalline quartz, SiO₂; chalcedony variety

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; brown, translucent to opaque, with waxy-to-glassy luster and no visible cleavage. The specimen appears water-worn and may show subtle banding, though its exact variety cannot be confirmed from the image.

Identified October 4, 2026More mineral →

Explore Brown chalcedony (likely carnelian/agate) in the encyclopedia →

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Physical properties

Formation & geological history

Silica-rich fluids deposited quartz in cavities or fractures; later weathering and transport may have rounded it. Chalcedony occurs in rocks of many ages and settings.

Uses & applications

Used for beads, cabochons, carvings, and ornaments; common rough material is also collected as a geological specimen.

Geological facts

Carnelian is typically orange-red chalcedony; brown chalcedony may be called sard or simply brown agate, depending on color and banding.

Field identification & locations

Look for a tough, waxy surface, translucent edges, and hardness near 7; it is commonly found in volcanic cavities and alluvial gravels worldwide. Image alone cannot establish whether it is banded agate or another chalcedony variety.