sedimentary

Chert (Flint)

Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 (Mohs scale); Color: Dark grey, brownish-black, or waxy translucent grey; Luster: Waxy to vitreous; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65.

Hardness: 7 (Mohs scale)
Color: Dark grey, brownish-black, or waxy translucent grey
Luster: Waxy to vitreous

Identified July 9, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed in sedimentary environments as a result of the accumulation of siliceous remains of organisms or chemical precipitation. This specific nodule likely formed within limestone or chalk beds during the Cretaceous period.

Uses & applications

Historically used for stone tools and weapons due to sharp edges; currently used as a fire starter (primitive survival), in road construction, and for jewelry/lapidary hobbies.

Geological facts

Chert and flint were among the first materials mined by humans. Because they fracture with very sharp edges (conchoidal), they were essential for making arrowheads and scrapers in the Stone Age.

Field identification & locations

Identify by its waxy texture and distinctive shell-like (conchoidal) fracture patterns when broken. It is often found as nodules inside limestone or as smooth pebbles in riverbeds.