sedimentary

Orbicular jasper (orbicular chert/jasper)

Silica-rich microcrystalline quartz (chalcedony), SiO₂, with iron-oxide and other mineral inclusions

AI-generated identification · may be incorrect

Typically Mohs 6.5–7; opaque, fine-grained, and waxy to dull-lustrous, with tan, olive, brown, black, and cream concentric orbicules. The rounded pebble shows no visible cleavage and likely consists of microcrystalline quartz with iron-rich matrix and possible chlorite or manganese minerals.

Identified August 16, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms when silica-rich volcanic or sedimentary material develops concentric mineral growths, later silicifies, and is weathered into a stream-rounded pebble. Exact age and locality cannot be determined from the photograph; orbicular jaspers occur in rocks ranging from Precambrian to younger volcanic sequences.

Uses & applications

Used as a lapidary stone for cabochons, carvings, polished slices, and collectible specimens; it has little industrial value compared with ordinary quartz.

Geological facts

Orbicular patterns are produced by repeated nucleation and replacement around small cores, creating eye-like or flower-like structures rather than true fossils.

Field identification & locations

Identify it by its hardness, opaque silica-rich body, and natural circular orbicules that remain visible when wet or polished; common sources include Madagascar, Mexico, Australia, Oregon, and South Africa.