mineral

Polished dendritic agate or jasper

Microcrystalline quartz (chalcedony), SiO₂, with iron/manganese oxide and possibly calcite veins

AI-generated identification · may be incorrect

Dark brown to black polished surface with irregular white mineral-filled seams; waxy to vitreous luster, cryptocrystalline structure, Mohs hardness about 6.5–7, no visible cleavage, and specific gravity near 2.6. The white areas may be quartz, calcite, or another contrasting matrix mineral.

Identified September 15, 2026More mineral →

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Physical properties

Formation & geological history

Likely formed when silica-rich fluids filled cavities or fractures in volcanic rock, with later deposition of contrasting minerals and iron/manganese staining. Exact age and locality cannot be determined from the photograph.

Uses & applications

Used as a cabochon, lapidary ornament, worry stone, or collectible; attractive patterned pieces may be set in jewelry. It has little industrial value as a small polished specimen.

Geological facts

The specimen’s strong contrast resembles brecciated or dendritic jasper, but visual identification alone cannot distinguish it reliably from agate or vein-filled chalcedony.

Field identification & locations

Field identification requires a conchoidal fracture, waxy luster, hardness sufficient to scratch glass, and resistance to dilute acid; acid bubbling would indicate calcite-rich white material. Common sources include volcanic terrains in Brazil, Mexico, Madagascar, India, and the western United States.