sedimentary

Yellow Jasper (Limonite-stained Chert)

Silicon Dioxide (SiO2) with Limonite/Goethite inclusions

Hardness: 6.5-7 (Mohs scale), Color: Mustard yellow to ochre orange with dark grey/green core, Luster: Dull to waxy, Crystal structure: Microcrystalline (Cryptocrystalline), Cleavage: None (conchoidal fracture), Specific gravity: 2.6-2.9

Hardness: 6

Identified March 26, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from the chemical precipitation of silica-rich fluids in volcanic ash or sedimentary beds. The yellow hue is caused by the hydration of iron oxides (limonite) during or after formation. Often found as stream-rounded cobbles from ancient deposits.

Uses & applications

Used primarily in lapidary work for cabochons, beads, and tumbled stones. Historically used by ancient cultures for tool making (knapping) due to its sharp fracture edges.

Geological facts

Jasper is categorized as an impure variety of silica. The rhythmic banding patterns seen on the side of this specimen are similar to 'picture jasper' formations, caused by the flow of mineral-rich water through the stone before it fully solidified.

Field identification & locations

Identify in the field by its inability to be scratched by a steel knife, its heavy weight for its size, and the smooth, rounded textures. Common in riverbeds (as seen here) or gravel pits. For collectors, look for unique patterns or 'landscape' banding.

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