mineral

Polished/tumbled brown stone, likely jasper or chert

Microcrystalline quartz (SiO₂), possibly iron-rich jasper or chert

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; chocolate-brown with darker patches, opaque, smooth rounded surface, and waxy to subvitreous luster. It has no visible cleavage and is composed of extremely fine quartz crystals.

Identified September 5, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich fluids replace or cement sediments, with iron oxides producing the brown coloration; commonly Precambrian to Cenozoic in age depending on source. The specimen has been mechanically tumbled or polished.

Uses & applications

Used for cabochons, beads, carvings, bookends, and decorative aggregate; small tumbled pieces have modest lapidary value.

Geological facts

Jasper and chert can be difficult to distinguish visually; jasper is generally more opaque and iron-stained, while chert may be more uniformly gray, brown, or translucent at thin edges.

Field identification & locations

Identify by its glassy/waxy polish, exceptional scratch resistance, opaque silica-rich body, and lack of fizz in dilute acid. Common worldwide, especially in sedimentary and volcanic terrains.