sedimentary

Chert (often called Flint or River Pebble)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: Tan, beige, brown; Luster: Waxy to dull; Crystal structure: Cryptocrystalline (microscopic); Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Hardness: 7 on Mohs scale
Color: Tan, beige, brown
Luster: Waxy to dull

Identified April 7, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale; Color: Tan, beige, brown; Luster: Waxy to dull; Crystal structure: Cryptocrystalline (microscopic); Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Formation & geological history

Formed by the precipitation of silica from groundwater or within biological remains in marine sedimentary environments. This specimen appears water-worn, likely from a stream or river bed.

Uses & applications

Historically used for stone tools and starting fires (striking steel). Modern uses include road aggregates, decorative landscaping stones, and tumbling for hobbyist collections.

Geological facts

Chert is so durable that it often survives long after the surrounding limestone or chalk has eroded away. Prehistoric humans prized it for its ability to fracture into razor-sharp edges.

Field identification & locations

Identify in the field by its smooth, waxy surface and its ability to scratch glass. This specific piece shows significant water erosion, creating a 'pitted' or 'pocketed' appearance. Common globally in sedimentary basins.