sedimentary

Chert (Flint)

Silicon dioxide (SiO2) - Microcrystalline Quartz

AI-generated identification · may be incorrect

Hardness: 6.5-7 on Mohs scale; Color: white, gray, orange, or brown; Luster: waxy to dull; Structure: microcrystalline; Cleavage: none (conchoidal fracture); Specific gravity: 2.65.

Hardness: 6
Color: white, gray, orange, or brown
Luster: waxy to dull

Identified July 14, 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: 6.5-7 on Mohs scale; Color: white, gray, orange, or brown; Luster: waxy to dull; Structure: microcrystalline; Cleavage: none (conchoidal fracture); Specific gravity: 2.65.

Formation & geological history

Formed through the accumulation of silica-rich organic remains or by the chemical precipitation of silica in groundwater within limestone or chalk beds. Often dated from the Paleozoic to Mesozoic eras.

Uses & applications

Historically used for stone tools and weapons (arrowheads); currently used as a raw material for road construction, in ceramics, and as a landscaping stone.

Geological facts

Chert was one of the most important minerals for early humans because its conchoidal fracture produces extremely sharp edges, ideal for cutting and skinning.

Field identification & locations

Identify in the field by its waxy appearance and the shell-like (conchoidal) curves where it has broken. Commonly found in riverbeds or as nodules within limestone outcrops.