sedimentary

Chert (Flint variety)

Microcrystalline or cryptocrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: Grey, tan, or white with a waxy or dull luster; Structure: Cryptocrystalline with conchoidal (shell-like) fracture; Cleavage: None.

Hardness: 7 on Mohs scale
Color: Grey, tan, or white with a waxy or dull luster

Identified July 9, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale; Color: Grey, tan, or white with a waxy or dull luster; Structure: Cryptocrystalline with conchoidal (shell-like) fracture; Cleavage: None.

Formation & geological history

Formed from the accumulation of silica-rich organic remains or through precipitation from silica-saturated fluids within limestone or chalk beds. Commonly found in sedimentary basins worldwide.

Uses & applications

Historically used for making stone tools (arrowheads, scrapers) and as a spark-starter for firearms; currently used in construction aggregate and as a collector's specimen.

Geological facts

Chert is so hard it can scratch steel or glass. Primitive humans favored it for its ability to produce sharp, durable edges when struck.

Field identification & locations

Identify in the field by its waxy appearance and shell-like curved fracture surfaces when broken. It is extremely common in areas with limestone bedrock.