mineral

Polished dendritic agate or jasper pebble

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

AI-generated identification · may be incorrect

Brown-and-cream, opaque to slightly translucent, waxy to glassy luster, nonmetallic; hardness about 6.5–7 Mohs, no visible cleavage, cryptocrystalline quartz structure. The rounded shape indicates tumbling or natural abrasion.

Identified August 27, 2026More mineral →

Explore Polished dendritic agate or jasper pebble in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Silica-rich groundwater filled cavities and fractures in volcanic rock, later depositing chalcedony and iron oxides; commonly formed during the Cenozoic or earlier, depending on locality.

Uses & applications

Used as a tumbled stone, cabochon, ornament, and lapidary material; attractive specimens may be collected, though this small piece has limited commercial value.

Geological facts

The white area may be quartz/chalcedony, while the dark brown material may be iron-stained jasper or agate. A glassy sheen and conchoidal fracture distinguish quartz-rich material from ordinary sedimentary rock.

Field identification & locations

Common in volcanic terrains and alluvial gravels, especially in Brazil, Uruguay, Mexico, India, Madagascar, and the western United States. Identify with a streak test, hardness test, and close inspection for translucency or banding; avoid scratching valuable specimens.