gemstone

Polished dendritic agate (likely moss agate)

Microcrystalline quartz, SiO₂, with iron/manganese oxide inclusions

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent gray-brown body with darker branching or cloudlike inclusions, vitreous/waxy luster, cryptocrystalline structure, and no visible cleavage. The smoothly rounded surface indicates tumbling and polishing.

Identified September 21, 2026More gemstone →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities in volcanic rocks, depositing chalcedony and quartz in layers; metallic oxides create the dendritic patterns. It commonly formed during Cenozoic to older volcanic episodes, depending on locality.

Uses & applications

Used for cabochons, beads, carvings, paperweights, and decorative objects; generally an affordable lapidary material.

Geological facts

Despite its plantlike patterns, dendritic agate contains mineral inclusions rather than fossils or actual vegetation. Color and pattern arise mainly from iron and manganese oxides.

Field identification & locations

Identify it by its waxy translucence, conchoidal fracture, fine banding or dendrites, and glass-scratching hardness; common sources include Brazil, India, Madagascar, Uruguay, and the United States. A loupe may reveal curved growth bands and inclusions.