sedimentary

Chert (Flint variety)

Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: Brown, tan, and gray; Luster: Waxy to dull; Crystal structure: Microcrystalline/Cryptocrystalline quartz; Cleavage: None (conchoidal fracture); Specific gravity: 2.6 – 2.65.

Hardness: 7 on Mohs scale
Color: Brown, tan, and gray
Luster: Waxy to dull

Identified January 13, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like diatoms or radiolarians) or chemical precipitation from groundwater within limestone or chalk beds. Most specimens date from the Phanerozoic eon.

Uses & applications

Historically used for stone tools and weapons (arrowheads). Modernly used in road construction, as architectural veneer, and in jewelry as 'Jasper' when brightly colored.

Geological facts

Chert is so hard it can create sparks when struck against steel, a property used for centuries to start fires. It is also the primary material for the world's oldest known manufactured tools.

Field identification & locations

Identify in the field by its smooth, shell-like (conchoidal) fracture surfaces and sharp edges. It will easily scratch glass. Commonly found as nodules or layers within sedimentary limestone outcrops globally.

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