sedimentary

Polished orbicular jasper / brecciated jasper

Jasper, microcrystalline quartz (SiO₂), with iron-oxide and clay-rich inclusions

AI-generated identification · may be incorrect

Opaque, rounded and polished, with cream, tan, brown, and black irregular bands or breccia-like patches. Quartz hardness is about 6.5–7 Mohs; vitreous to dull waxy luster, cryptocrystalline structure, and no visible cleavage. The dark areas are likely iron/manganese oxides or matrix minerals.

Identified August 12, 2026More sedimentary →

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Physical properties

Formation & geological history

Jasper forms when silica-rich fluids replace or cement volcanic ash, sediments, or brecciated rock; iron and manganese create the contrasting colors. Exact age cannot be determined visually. Such material is common in western North America, including California, though this specimen may have been collected or commercially sourced elsewhere.

Uses & applications

Used as a lapidary stone for polished pieces, cabochons, spheres, bookends, and ornamental objects; generally not used structurally. Common polished specimens typically sell for about $10–$40, with larger or unusually patterned pieces reaching $50–$150.

Geological facts

The image most strongly suggests jasper rather than a single crystalline mineral. A hardness or streak test can help distinguish it from softer painted or resin-coated material.

Field identification & locations

Field identification: opaque, silica-hard, fine-grained material that does not fizz in dilute hydrochloric acid and leaves a white streak. Near 38.7°N, 121.3°W, stream gravels and Sierra foothill materials can contain varied jasper and chert, but the precise locality cannot be confirmed from appearance alone.