mineral

Tumbled brown chalcedony (likely jasper or chert)

Microcrystalline quartz, SiO₂; opaque varieties are commonly called jasper or chert

AI-generated identification · may be incorrect

Smooth, rounded, opaque brown specimen with dull-to-waxy luster and fine-grained texture; quartz hardness is about Mohs 7, with no visible cleavage and conchoidal fracture. Exact identification is limited by the photograph; the glossy surface may be polished or naturally water-worn.

Identified September 21, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities or replaces sediment, producing microcrystalline quartz; iron oxides commonly create the brown color. Formation ages vary widely, from relatively young deposits to Precambrian rocks.

Uses & applications

Used for cabochons, beads, carvings, tumbling, and decorative objects; jasper and chert are also used as minor ornamental stone and historically for tools.

Geological facts

A magnet typically does not attract it, and a steel file should not easily scratch it if it is quartz-rich. Brown coloration usually reflects hematite or goethite inclusions.

Field identification & locations

Common in gravel beds, volcanic cavities, and sedimentary formations worldwide; test streak, hardness, and translucency, and inspect a fresh chip for waxy luster or conchoidal fracture.