mineral

Brown chalcedony (likely agate)

Microcrystalline quartz, SiO₂; chalcedony, possibly banded agate

AI-generated identification · may be incorrect

Glossy, translucent-to-opaque brown material with waxy luster and curved fracture surfaces. Mohs hardness about 6.5–7; trigonal quartz crystals are microscopic, and cleavage is absent. The photo does not show clear banding, so exact identification is uncertain.

Identified October 4, 2026More mineral →

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Physical properties

Formation & geological history

Silica-rich fluids deposited quartz in cavities or fractures, commonly in volcanic rocks; the specimen’s age and precise source cannot be determined from the image.

Uses & applications

Used for jewelry, carvings, ornamental objects, and mineral collecting; rough pieces of this apparent size are generally modestly valued.

Geological facts

Chalcedony is a compact variety of quartz, and agate is typically distinguished by visible bands or patterns.

Field identification & locations

Look for hardness near 7, a glassy-to-waxy surface, and conchoidal (curved, shell-like) fracture; agate often has distinct bands. Chalcedony occurs worldwide, including Brazil, Uruguay, India, and the western United States.