sedimentary

Orbicular jasper (orbicular chert), likely ocean jasper

Silicified microcrystalline quartz (chalcedony), SiO₂, with iron-oxide and/or clay-rich orbicules

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; cream to yellow matrix with gray-brown rounded orbicules, waxy to dull luster, opaque, and no obvious cleavage. The visible pattern consists of contrasting concentric or rounded silica-rich bodies in a fine-grained chalcedonic matrix.

Identified August 10, 2026More sedimentary →

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At a glance

Common name: Orbicular jasper (orbicular chert), likely ocean jasper
Scientific name: Silicified microcrystalline quartz (chalcedony), SiO₂, with iron-oxide and/or clay-rich orbicules
Category: sedimentary
Identified: August 10, 2026
Method: Standard

AI Estimated Value

About $5–$25 for a small rough piece; attractive patterned lapidary-grade material may sell for $20–$100 or more.

Not an official valuation

AI estimate for general interest only — not an appraisal. Actual value depends on condition, provenance, and market demand. Verify with a professional before buying, selling, or insuring.

This identification was generated by AI and may contain errors. Verify important details before relying on them — and never use an AI result to judge whether a specimen is safe to handle. Read the full disclaimer

Physical properties

Formation & geological history

Forms when silica-rich fluids replace or cement volcanic ash, sediment, or carbonate material, producing orbicular textures during diagenesis and silicification. Orbicular jasper commonly formed in volcanic environments, generally in the Cenozoic or older, depending on locality.

Uses & applications

Used for cabochons, beads, carvings, decorative slabs, and collected as an ornamental stone; it has little industrial value compared with ordinary quartz.

Geological facts

“Ocean jasper” is a trade name often applied to orbicular jasper from Madagascar, though visually similar orbicular cherts and jaspers occur elsewhere. The specimen appears rough and naturally fractured rather than polished.

Field identification & locations

Identify it by its opaque chalcedony-like body, rounded contrasting orbicules, fine grain, and ability to scratch glass; acid usually produces little or no reaction. Common sources include Madagascar, Mexico, Australia, and parts of the western United States.