sedimentary

Flint / Chert Pebble

Microcrystalline Quartz (SiO2)

Hardness: 7 on the Mohs scale. Color: Shades of brown, grey, and white with distinctive banding. Luster: Vitreous to waxy. Crystal structure: Trigonal (microcrystalline/cryptocrystalline quartz). Cleavage: None, exhibits conchoidal fracture. Specific gravity: 2.60 to 2.65.

Hardness: 7 on the Mohs scale
Color: Shades of brown, grey, and white with distinctive banding
Luster: Vitreous to waxy

Identified August 5, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the chemical precipitation of silica from seawater, replacing calcium carbonate in limestone or chalk formations during the Cretaceous period.

Uses & applications

Historically used for making stone tools, arrowheads, and fire-starting (flint and steel). Currently used in abrasive products, road construction, and as a decorative stone.

Geological facts

Flint is extremely durable and breaks with sharp conchoidal fractures, which made it the primary material for prehistoric humans crafting cutting and hunting tools.

Field identification & locations

Easily identified by its waxy luster, conchoidal fracture edges, and high hardness that can scratch glass. Commonly found along chalk cliffs, beaches, and riverbeds.

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