sedimentary

Chert (Yellow Jasper variant)

Microcrystalline or cryptocrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 (Mohs scale), Color: translucent yellow to tan, Luster: waxy to dull, Crystal structure: Trigonal (microscopic), Cleavage: None (conchoidal fracture), Specific gravity: 2.65

Identified March 20, 2026More sedimentary →

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Physical properties

Hardness: 7 (Mohs scale), Color: translucent yellow to tan, Luster: waxy to dull, Crystal structure: Trigonal (microscopic), Cleavage: None (conchoidal fracture), Specific gravity: 2.65

Formation & geological history

Formed via the accumulation of silica-rich organic remains (like radiolaria or diatoms) or chemical precipitation in marine environments. It can occur across many geological ages from Precambrian to Cenozoic.

Uses & applications

Historically used for stone tools/arrowheads due to sharp edges; currently used for decorative stone, lapidary jewelry, and landscaping. High silica content makes it useful in some industrial abrasives.

Geological facts

Chert is so durable that it often survives intense weathering that destroys surrounding rocks. It was one of the most vital materials for early humans because its conchoidal fracture allows it to be knapped into extremely sharp tools.

Field identification & locations

Identify in the field by its waxy luster and smooth, curved (conchoidal) fracture surfaces that resemble broken glass. Found globally in limestone beds or as nodules and pebbles in riverbeds. It cannot be scratched by a steel knife.