sedimentary

Chert (varietal: Flint Pitted Pebble)

Cryptocrystalline Quartz (SiO2)

Hardness: 7 (Mohs scale); Color: Creamy white exterior with grey/brown pits; Luster: Waxy to dull; Structure: Cryptocrystalline (no visible crystals); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65.

Hardness: 7 (Mohs scale)
Color: Creamy white exterior with grey/brown pits
Luster: Waxy to dull

Identified March 21, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the precipitation of silica within sedimentary limestone or chalk layers. This specimen likely weathered out of its host rock, being smoothed and pitted by water transport in a river or coastal environment.

Uses & applications

Historically used for stone tools and fire-starting; currently used as construction aggregate, road surfacing, and occasionally as decorative landscaping stones.

Geological facts

Because it is composed of microcrystalline quartz, it is extremely chemically stable. The pits on the surface are often the result of water dissolving softer inclusions or 'vugs' within the rock over thousands of years.

Field identification & locations

Identify in the field by its hardness (cannot be scratched by a steel knife) and smooth, rounded water-worn shape. It is commonly found in gravel pits, riverbeds, and chalk-rich coastal regions like southern England or the US Midwest.

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