sedimentary

Chert (Jasper/Flint variety)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs scale), Color: Brown, grey, and rusty orange (iron staining), Luster: Waxy to dull, Structure: Cryptocrystalline, Cleavage: None (conchoidal fracture)

Hardness: 6

Identified June 21, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 (Mohs scale), Color: Brown, grey, and rusty orange (iron staining), Luster: Waxy to dull, Structure: Cryptocrystalline, Cleavage: None (conchoidal fracture)

Formation & geological history

Forms through the accumulation of silica-rich microfossils or via chemical precipitation from silica-saturated groundwater within sedimentary layers. This water-worn pebble likely originated in a riverbed or coastal environment.

Uses & applications

Historically used for stone tools and strike-a-lights; currently used as decorative gravel, in lapidary work (polishing), and as industrial abrasives.

Geological facts

Chert is so hard it can scratch glass and steel. It was one of the most vital materials for early humans because of its ability to break into sharp, durable edges called conchoidal fractures.

Field identification & locations

Identify in the field by its smooth, waxy feel and shell-like (conchoidal) breaks. It will not be scratched by a steel knife. Commonly found in riverbeds, gravel pits, and limestone formations.