mineral

Polished dendritic agate or jasper

Microcrystalline quartz (SiO₂), likely chalcedony/agate with iron-oxide inclusions

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; opaque gray-brown body with a contrasting white chalcedony band, glassy to waxy luster, cryptocrystalline structure, and no visible cleavage. The rounded, glossy surface indicates tumbling and polishing.

Identified September 15, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures in volcanic rocks, depositing layered chalcedony and quartz over time; iron oxides create brown coloration. The specimen’s exact geological age cannot be determined from the image.

Uses & applications

Used as a low-cost ornamental stone for cabochons, beads, carvings, and display pieces; polished specimens are mainly valued for pattern and color.

Geological facts

The white zone may be a quartz/chalcedony vein rather than a true agate band, while the brown matrix resembles jasper. A proper identification requires testing or examination of an unpolished edge.

Field identification & locations

Commonly found in volcanic terrains and alluvial gravels, especially Brazil, Uruguay, India, Madagascar, and the western United States. Field clues include waxy luster, very fine grain, strong toughness, and inability to scratch with a steel knife; it should scratch glass.