gemstone

Polished dendritic agate or jasper cabochon

Microcrystalline quartz, SiO₂, likely chalcedony with iron/manganese oxide inclusions

AI-generated identification · may be incorrect

A polished, translucent-to-opaque gray-white stone with dark branching or mossy inclusions and a vitreous-to-waxy luster; quartz hardness is about 6.5–7 Mohs, with no visible cleavage and conchoidal fracture. The exact variety is uncertain because the image is small and the specimen is mounted or resting on fabric.

Identified August 26, 2026More gemstone →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures in volcanic rock, while manganese or iron oxides create dendritic patterns; deposition commonly occurred during volcanic activity from the Cenozoic to older Phanerozoic eras. Common sources include India, Brazil, Uruguay, Mexico, Madagascar, and the western United States.

Uses & applications

Used for cabochons, beads, carvings, ornaments, and lapidary collections; it is not generally used in construction.

Geological facts

Dendritic markings are mineral growth patterns, not fossil plants. A gemological loupe, hardness test, and examination of translucency and banding help distinguish dendritic agate from dendritic jasper or imitation glass.

Field identification & locations

Look for natural irregular inclusions, waxy translucency, conchoidal edges, and quartz-like hardness; avoid scratching the polished face when testing. Common quality specimens typically show strong contrast and attractive patterning.