sedimentary

Chert (often called Flint in archaeological contexts)

Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 (Mohs scale); Color: Tan, beige, white, and translucent; Luster: Waxy to dull; Crystal Structure: Cryptocrystalline (microscopic quartz); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65.

Hardness: 7 (Mohs scale)
Color: Tan, beige, white, and translucent
Luster: Waxy to dull

Identified April 6, 2026More sedimentary →

Explore Chert (often called Flint in archaeological contexts) in the encyclopedia →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like radiolarians or diatoms) or chemical precipitation from groundwater within carbonate host rocks like limestone. It can form as nodules or bedded layers.

Uses & applications

Historically used for stone tools (arrowheads, scrapers) and starting fires. Modern use includes road surfacing, grinding media, and as a semi-precious gemstone when colorful.

Geological facts

Chert breaks with a conchoidal (shell-like) fracture, creating razor-sharp edges. This property made it the primary material for tool-making during the Stone Age.

Field identification & locations

Identify in the field by its waxy texture and the way it chips away in curved, shallow bowls. It will easily scratch glass and generate sparks when struck against steel.