mineral

Polished brown agate or jasper

Microcrystalline quartz, SiO₂ (chalcedony variety; exact identification uncertain)

AI-generated identification · may be incorrect

Dark brown, opaque to slightly translucent, with a glossy polished surface and fine-grained texture; quartz hardness is about 6.5–7 Mohs, no visible cleavage, conchoidal fracture, and specific gravity near 2.6. The specimen may contain iron-oxide staining or inclusions.

Identified August 28, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures in volcanic rocks, followed by slow deposition of chalcedony and quartz. Its precise geological age cannot be determined from the photograph; agates and jaspers occur from Precambrian to recent rocks.

Uses & applications

Used for cabochons, carvings, beads, ornaments, and lapidary collectibles; jasper and agate are also used decoratively in tiles and small architectural objects.

Geological facts

Agate typically shows banding or translucency, whereas jasper is more uniformly opaque and earthy. The strong polish and rounded edges indicate human lapidary processing.

Field identification & locations

Commonly found in volcanic terrains, especially Brazil, Uruguay, India, Madagascar, Mexico, and the western United States. Check hardness, streak, translucency at thin edges, and internal banding; iron-rich brown coloration alone is not diagnostic.