sedimentary

Yellow Chert (River Stone)

Chert (SiO2)

Hardness: 6.5-7 (Mohs), Color: Yellow to brownish-tan, Luster: Waxy to dull, Structure: Cryptocrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.6

Hardness: 6

Identified May 25, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 (Mohs), Color: Yellow to brownish-tan, Luster: Waxy to dull, Structure: Cryptocrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.6

Formation & geological history

Formed through the accumulation of silica-rich organic remains or chemical precipitation from groundwater within sedimentary layers. This specific specimen shows significant tumbling and smoothing from river transport.

Uses & applications

Used historically for stone tools due to its sharp edges; currently used for landscaping, aggregate in construction, and as decorative river stones.

Geological facts

Chert is so durable that it is often the primary rock left behind in riverbeds after softer rocks have eroded away. Native Americans frequently used this type of yellow jasper-like chert for scraping tools.

Field identification & locations

Identify in the field by its waxy appearance and inability to be scratched by a steel knife. Commonly found in riverbeds, gravel pits, and sedimentary outcrops globally.