sedimentary

Yellow Chert (Gold-toned Jasper)

Silicon Dioxide (SiO2)

Hardness: 6.5 - 7 on the Mohs scale. Color: Opaque mustard yellow to brown-gold. Luster: Dull to waxy. Structure: Microcrystalline/Cryptocrystalline quartz. Cleavage: None (conchoidal fracture). Specific gravity: 2.6 - 2.7.

Hardness: 6
Color: Opaque mustard yellow to brown-gold
Luster: Dull to waxy

Identified March 24, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich microfossils (like radiolaria or diatoms) or by the chemical precipitation of silica in groundwater. This specimen is typically found in stream beds or gravel deposits. Geological age varies widely from Precambrian to Cenozoic.

Uses & applications

Historically used for stone tools and arrowheads because of its sharp conchoidal edges; currently used for tumbled stones, lapidary jewelry, garden landscaping, and as a collector's specimen.

Geological facts

Chert is so durable that it is often found as 'river rock' long after the surrounding softer rocks have eroded away. Native cultures prized the yellow/gold variants for their aesthetic and functional properties.

Field identification & locations

Identify in the field by its extreme hardness (cannot be scratched by a steel knife) and its smooth, shell-like (conchoidal) breakage patterns. Common in gravel pits and river banks globally. Look for a waxy texture when wet.

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