sedimentary

Chert / Flint

Chert (Microcrystalline Quartz, SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: Grey, brown, white; Luster: Waxy to vitreous; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 on Mohs scale
Color: Grey, brown, white
Luster: Waxy to vitreous

Identified June 3, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale; Color: Grey, brown, white; Luster: Waxy to vitreous; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Formation & geological history

Formed as nodules in sedimentary rocks like limestone or chalk through the precipitation of silica from groundwater or organic remains (radiolarians/diatoms) during the Paleozoic to Cenozoic eras.

Uses & applications

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

Geological facts

Flint was the primary material for prehistoric technology for over 2 million years. It creates sharp edges when struck and sparks when hit against steel.

Field identification & locations

Identify by its 'waxy' appearance and smooth, shell-like (conchoidal) curved breaks. Found globally in chalk and limestone beds or as rounded pebbles in stream beds/beaches.