mineral

Polished brown agate or jasper

Microcrystalline quartz, SiO₂ (chalcedony variety; exact identification uncertain from image)

AI-generated identification · may be incorrect

Opaque to translucent brown, cream, and reddish banding with a waxy to glossy luster; hardness about 6.5–7 Mohs, no visible cleavage, and conchoidal fracture. The rounded shape and smooth surface indicate tumbling or polishing.

Identified September 13, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities or fractures in volcanic rocks, depositing chalcedony and sometimes iron oxides in successive bands. Formation generally occurred during cooling and later groundwater activity, with age dependent on its source locality.

Uses & applications

Used for cabochons, carvings, ornamental objects, and lapidary collections; less commonly for industrial silica. Value is usually modest unless patterns, translucency, or provenance are exceptional.

Geological facts

Brown coloration commonly comes from iron oxides or hydroxides. Agate is banded chalcedony, whereas jasper is generally more uniformly opaque; this specimen may be an agate–jasper variety.

Field identification & locations

Look for curved or concentric banding, a waxy surface, and glassy conchoidal edges; it should scratch glass but not be scratched by a steel knife. Common sources include Brazil, Uruguay, Mexico, India, Madagascar, and the western United States.