sedimentary

Chert Pebble

Microcrystalline Quartz (SiO2)

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

Hardness: 7 Mohs scale
Color: Tan, beige, and grey
Luster: Waxy to dull

Identified June 22, 2026More sedimentary →

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Physical properties

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

Formation & geological history

Formed via the accumulation of silica-rich organic remains (like diatoms or radiolarians) or chemical precipitation in marine environments. This specific specimen is a water-worn river pebble likely originating from Paleozoic or Mesozoic strata.

Uses & applications

Historically used for stone tools (arrowheads). Modern uses include aggregate in construction, road surfacing, and as tumbling media for beginners in rock hounding.

Geological facts

Chert is the common parent material for flint and jasper. It is so tough that it was one of the primary materials used by prehistoric humans to create fire and sharp cutting tools.

Field identification & locations

Identify by its extreme hardness (cannot be scratched by a steel nail) and its smooth, waxy surface. Commonly found in riverbeds, glacial tills, and limestone outcrops globally.