sedimentary

Chert / River Jasper

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs scale), Color: tan, grey, brown with iron staining, Luster: waxy to dull, Crystal structure: cryptocrystalline, Cleavage: none (conchoidal fracture), Specific gravity: 2.65

Hardness: 6

Identified July 19, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 (Mohs scale), Color: tan, grey, brown with iron staining, Luster: waxy to dull, Crystal structure: cryptocrystalline, Cleavage: none (conchoidal fracture), Specific gravity: 2.65

Formation & geological history

Formed by the accumulation of siliceous remains of organisms or through chemical precipitation in sedimentary environments. These rounded specimens are typically weathered in riverbeds or coastal regions.

Uses & applications

Historically used for stone tools due to sharp edges when fractured; modernly used as aggregate, landscaping stone, or tumbled for hobbyists.

Geological facts

Chert is extremely durable and chemically stable, allowing it to survive millions of years of river erosion. It is often found as nodules within limestone formations.

Field identification & locations

Identify in the field by its smooth, waxy texture and conchoidal (shell-like) fracture patterns. Often found in gravel driveways or riverbanks. It cannot be scratched by a steel knife.