sedimentary

Chert / Flint

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Hardness: 7 on Mohs scale; Color: Tan, brown, or honey-colored in this specimen; Luster: Waxy to dull; Crystal structure: Trigonal (microscopic); Cleavage: None (conchoidal fracture); Specific gravity: 2.6–2.7

Hardness: 7 on Mohs scale
Color: Tan, brown, or honey-colored in this specimen
Luster: Waxy to dull

Identified March 20, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich biogenic materials (like radiolaria or diatoms) or by chemical precipitation in groundwater that replaces limestone or chalk. It can be found in rocks from the Precambrian to the present.

Uses & applications

Historically used for stone tools (arrowheads, knives) due to its sharp edges. Currently used in road construction, as a component in ceramics, and occasionally as a semi-precious gemstone in jewelry when it displays interesting patterns (Jasper).

Geological facts

Flint is a variety of chert that was essential to human evolution, providing the primary material for the Neolithic tool industry and a reliable method for sparking fires when struck against steel.

Field identification & locations

Identify in the field by its distinct 'shell-like' conchoidal fracture patterns and the fact that it can easily scratch glass. It is commonly found in limestone or chalk beds globally, often occurring as nodules or thick beds.

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