sedimentary

Chert / Flint

Silicon Dioxide (SiO2)

Hardness: 7 on the Mohs scale; Color: typically gray, brown, tan, or white; Luster: waxy or dull; Crystal Structure: Cryptocrystalline (microscopic quartz); Cleavage: none (exhibits conchoidal fracture); Specific Gravity: 2.65.

Hardness: 7 on the Mohs scale
Color: typically gray, brown, tan, or white
Luster: waxy or dull

Identified March 18, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich organic debris (such as radiolarian or sponge spicules) on the ocean floor, or via chemical precipitation within limestone or chalk beds. Geological age ranges from Precambrian to Cenozoic.

Uses & applications

Historically used for making stone tools (arrowheads, knives) due to its sharp edges; used in striking fire; currently used as road construction aggregate and in grinding media.

Geological facts

Flint is a variety of chert that occurs primarily in chalk or marly limestone. It was the vital 'high-tech' material of the Stone Age, allowing early humans to create advanced weaponry and tools.

Field identification & locations

Identify in the field by its very hard surface (can scratch glass), smooth shell-like (conchoidal) fractures, and waxy texture. Commonly found in riverbeds, glacial deposits, and embedded in limestone cliffs.