sedimentary

Chert (Flint)

Chert (Microcrystalline Silica, SiO2)

AI-generated identification · may be incorrect

Hardness: 7 (Mohs scale); Color: Gray, tan, white, brown; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65.

Hardness: 7 (Mohs scale)
Color: Gray, tan, white, brown
Luster: Waxy to dull

Identified June 30, 2026More sedimentary →

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Physical properties

Hardness: 7 (Mohs scale); Color: Gray, tan, white, brown; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65.

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like diatoms or radiolarians) or by chemical precipitation from ground fluids in limestone or chalk beds. Most common in Paleozoic and Mesozoic strata.

Uses & applications

Historically used for stone tools (arrowheads, scrapers) and fire-starting. Currently used in road construction, as a gemstone (Jasper/Agate varieties), and in landscaping.

Geological facts

Chert is so hard it can scratch glass and steel. It was one of the most vital resources for prehistoric humans due to its ability to produce razor-sharp edges when fractured.

Field identification & locations

Identify by its 'shell-like' conchoidal fracture patterns and waxy texture. It is frequently found as nodules or layers within limestone outcrops or as river-worn cobbles.