sedimentary

Chert (Iron-rich River Pebble)

Cryptocrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 Mohs. Color: Dull brown to reddish-brown (likely due to iron oxide staining). Luster: Waxy to dull. Crystal structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific gravity: 2.65.

Hardness: 6
Luster: Waxy to dull

Identified June 25, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from the accumulation of microscopic silica-rich organisms or chemical precipitation. This specific piece has been water-worn into a smooth pebble shape in a fluvial (river) environment, likely over thousands of years.

Uses & applications

Primarily used as decorative stone in landscaping or river rock; historically used for stone tools like scrapers and arrowheads due to its conchoidal fracture.

Geological facts

Chert is so durable that it often survives as a pebble long after the original parent rock has weathered away. It is closely related to flint, jasper, and agate.

Field identification & locations

Identify in the field by its hardness (will scratch glass) and smooth, rounded water-worn texture. Commonly found in riverbeds, gravel pits, and coastal areas throughout North America and Europe.