sedimentary

Chert (Flint)

Chert (Microcrystalline Quartz, SiO2)

AI-generated identification · may be incorrect

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

Hardness: 7 on Mohs scale
Color: Cream, white, gray, tan
Luster: Waxy to dull

Identified April 7, 2026More sedimentary →

Explore Chert (Flint) 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: Cream, white, gray, tan; 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 radiolaria or diatoms) 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 (knapping) and fire-starting. Currently used in road surfacing, as a gemstone (Jasper), and for historical artifacts.

Geological facts

Chert was one of the most important minerals for early humans due to its ability to fracture into sharp edges. It is chemically identical to quartz but has a different internal structure.

Field identification & locations

Identify by its waxy texture and distinctive shell-like (conchoidal) curved fractures. Often found as nodules within limestone or as river-worn pebbles. It will easily scratch glass.