sedimentary

Chert (River Pebble)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs scale); Color: Brown, tan, or grey; Luster: Dull to waxy; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 6
Color: Brown, tan, or grey
Luster: Dull to waxy

Identified July 18, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 (Mohs scale); Color: Brown, tan, or grey; Luster: Dull to waxy; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Formation & geological history

Formed through the accumulation of silica-rich organic remains or chemical precipitation within sedimentary layers. This specific specimen is a water-worn river pebble, shaped by fluvial erosion over thousands of years.

Uses & applications

Historically used for stone tools (arrowheads). Modern uses include construction aggregate, road base, and occasionally decorative landscaping.

Geological facts

Chert is extremely durable and chemically stable. Because it breaks with a sharp edge, it was one of the most important minerals for early human survival for making tools and starting fires (flint is a variety of chert).

Field identification & locations

Identify by its hardness (it will scratch glass) and its smooth, rounded surface from water tumbling. Often found in riverbeds, glacial till, and coastal areas.