sedimentary

Chert (Commonly known as Flint)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: Brown, tan, and gray waxy tones; Luster: Dull to sub-vitreous (waxy); Crystal Structure: Cryptocrystalline; Cleavage: None (Conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 on Mohs scale
Color: Brown, tan, and gray waxy tones
Luster: Dull to sub-vitreous (waxy)

Identified February 22, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms primarily through the accumulation of silica-rich organic remains (like diatoms or radiolarians) or chemical precipitation in sedimentary environments. Common in limestone or chalk beds, found in strata ranging from Precambrian to recent geological ages.

Uses & applications

Historically used for stone tools (knapping) and fire-starting. Currently used as a road aggregate, in jewelry as semi-precious gemstones (jaspers), and in some glass-making or abrasive industrial processes.

Geological facts

Flint is a variety of chert that has been vital to human evolution, providing the primary material for spearheads and arrowheads for millennia. It produces sparks when struck against steel due to the hardness causing minute particles of metal to ignite.

Field identification & locations

Identify by its characteristic conchoidal (shell-like) fracture and sharp edges. It will scratch glass easily. Commonly found in river beds, gravel pits, or embedded as nodules within limestone and chalk outcroppings.