sedimentary

Chert

Microcrystalline silica (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: Sage green, grey, or tan; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Hardness: 7 on Mohs scale
Color: Sage green, grey, or tan
Luster: Waxy to dull

Identified May 7, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale; Color: Sage green, grey, or tan; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Formation & geological history

Formed from the accumulation of siliceous remains of marine organisms or via chemical precipitation in sedimentary environments. Common in marine limestone formations.

Uses & applications

Used historically for stone tools and weapons due to its sharp edges; industrially used as an abrasive or in road construction; popular for lapidary work.

Geological facts

Also known as flint when found in chalk. It was one of the first materials used by prehistoric humans to create fire and sharp arrowheads because it produces sparks and predictable fractures.

Field identification & locations

Identify by its ability to scratch glass and its shell-like (conchoidal) fracture patterns. Frequently found in riverbeds or as nodules within limestone outcrops.