sedimentary

Chert (Flint)

Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 (Mohs scale), Color: Grey, brown, or waxy olive-green, Luster: Vitreous to waxy, Crystal Structure: Microcrystalline/Cryptocrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7

Identified June 5, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed as nodules or layers in sedimentary rocks (like limestone or chalk) through the precipitation of silica from groundwater or accumulation of siliceous organisms like diatoms and radiolarians.

Uses & applications

Historically used for stone tools and weapons (arrowheads/scrapers) and as a spark-generator (flint and steel). Modern uses include road surfacing and as a gemstone when colorful (Jasper).

Geological facts

The conchoidal fracture of chert produces sharp edges, which made it a critical material for human survival during the Stone Age. It is chemically identical to quartz but has a different internal structure.

Field identification & locations

Identify in the field by its smooth, shell-like fracture surfaces (conchoidal) and its ability to scratch glass. It is often found as pods or layers within chalk or limestone formations.