gemstone

Tumbled dendritic agate (likely Montana or moss agate)

Microcrystalline quartz, SiO₂, with iron/manganese-oxide dendrites

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent gray-beige body with dark branching or speckled inclusions, vitreous/waxy luster, cryptocrystalline structure, and no visible cleavage. Specific gravity is approximately 2.60–2.65.

Identified September 16, 2026More gemstone →

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Physical properties

Formation & geological history

Silica-rich groundwater filled cavities and fractures in volcanic rock, later depositing chalcedony and oxide dendrites over long geological periods, commonly in the Cenozoic or older volcanic terrains.

Uses & applications

Used as a tumbled collectible, cabochon, bead, and ornamental stone; generally modestly valued unless patterns, translucency, and polish are exceptional.

Geological facts

The dark markings are usually manganese or iron oxides, not fossils or plant material, although dendritic patterns can resemble botanical forms.

Field identification & locations

Identify by its waxy translucent chalcedony, rounded tumble polish, and inclusions that remain within the stone rather than appearing as surface paint. Common sources include Montana, Oregon, Wyoming, Brazil, India, and Madagascar.