sedimentary

Orbicular jasper

Silicified volcanic or sedimentary rock, primarily microcrystalline quartz (SiO₂) with iron-oxide-rich orbicules

AI-generated identification · may be incorrect

Typically hardness 6.5–7 Mohs, opaque brown to reddish-orange, with cream or darker rounded orbicules and a dull to waxy luster; lacks obvious cleavage and has a dense, fine-grained structure.

Identified August 14, 2026More sedimentary →

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Physical properties

Typically hardness 6.5–7 Mohs, opaque brown to reddish-orange, with cream or darker rounded orbicules and a dull to waxy luster; lacks obvious cleavage and has a dense, fine-grained structure.

Formation & geological history

Forms when silica-rich fluids replace or cement volcanic ash, breccia, or sediment, producing concentric mineral growths; exact age depends on locality, commonly Paleozoic to Cenozoic.

Uses & applications

Used for cabochons, beads, carvings, lapidary slabs, and decorative stone; attractive patterned pieces are primarily collector or jewelry materials rather than construction stone.

Geological facts

The circular patterns are orbicules, commonly composed of chalcedony, quartz, feldspar, and iron oxides; “jasper” is a broad lapidary term for opaque, silica-rich chert.

Field identification & locations

Identify it by its opaque body, reddish-brown iron staining, hardness, and rounded orbicular patterns; common sources include Madagascar, Mexico, Oregon, Utah, and Australia. A steel file should not easily scratch it.