mineral

Tumbled brown agate or jasper

Microcrystalline quartz (SiO₂), likely iron-stained chalcedony

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; dark brown to reddish-brown, opaque to slightly translucent, with a glassy-to-waxy luster and no visible cleavage. The smoothly rounded, wet surface may exaggerate its polish and color.

Identified September 5, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities or fractures, later solidifying as chalcedony or fine quartz; iron oxides create the brown coloration. Such material commonly formed in volcanic rocks over millions of years, though the specimen appears naturally water-worn or tumbled.

Uses & applications

Used for cabochons, beads, carvings, decorative stone, and inexpensive collecting specimens; polished pieces typically have modest commercial value.

Geological facts

Agate is banded chalcedony, while jasper is generally opaque and more granular; a cut surface would best reveal whether banding is present.

Field identification & locations

Common in volcanic terrains, stream gravels, and gravel deposits worldwide, including Brazil, Uruguay, India, Madagascar, and the western United States. Test cautiously with a steel file or streak comparison: quartz-rich material resists scratching and leaves no colored streak.