sedimentary

Chert (variations include Flint or Jasper)

Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: Brown, tan, or gray; Luster: Waxy to dull; Crystal structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7

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

Identified March 14, 2026More sedimentary →

Explore Chert (variations include Flint or Jasper) in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Hardness: 7 on Mohs scale; Color: Brown, tan, or gray; Luster: Waxy to dull; Crystal structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like diatoms or radiolarians) or by chemical precipitation in groundwater that replaces limestone or chalk. Can be found in geological strata ranging from Precambrian to Cenozoic.

Uses & applications

Historically used for stone tools and weapons (arrowheads); currently used as a raw material in road construction, as a gemstone (jasper varieties), and as fire-starting flint.

Geological facts

Chert is so hard it can scratch glass and steel. Because it breaks with a conchoidal fracture like glass, it creates extremely sharp edges, which is why it was the primary choice for Neolithic tools.

Field identification & locations

Identify in the field by its smooth, waxy feel and the way it breaks into curved, shell-like (conchoidal) shards. Commonly found in riverbeds or as nodules within limestone outcrops globally.