sedimentary

Flint Pebble

Silicon Dioxide (Microcrystalline Quartz / Chert)

Hardness: 7 on the Mohs scale. Color: Brownish-grey, weathered outer cortex. Luster: Waxy to vitreous on fresh fractures, dull on weathered surfaces. Crystal structure: Cryptocrystalline (microscopic quartz crystals). Cleavage: None, exhibits conchoidal fracture. Specific gravity: 2.60 to 2.65.

Hardness: 7 on the Mohs scale
Color: Brownish-grey, weathered outer cortex

Identified August 5, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the replacement of calcium carbonate by silica-rich solutions in marine chalk or limestone environments during the Cretaceous period, followed by weathering and wave action smoothing it into a pebble.

Uses & applications

Historically used for prehistoric stone tools, arrowheads, and firearm ignition (flintlock). Today used in specialized grinding mills and as decorative landscaping or coastal shingle.

Geological facts

Flint is famous for producing sharp-edged flakes when struck (knapping) and creates sparks when hit against steel due to its high hardness.

Field identification & locations

Commonly found on chalk cliffs, beaches, and riverbeds. Identified by its conchoidal fracture, waxy luster on broken surfaces, and extreme hardness that easily scratches glass.

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