sedimentary

Chert (Iron-Stained)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7.0 (Mohs scale); Color: tan, yellow, orange, or brown from iron oxides; Luster: waxy to dull; Structure: microcrystalline/cryptocrystalline; Cleavage: none (conchoidal fracture); Specific Gravity: 2.6-2.7.

Hardness: 6
Color: tan, yellow, orange, or brown from iron oxides
Luster: waxy to dull

Identified March 19, 2026More sedimentary →

Explore Chert (Iron-Stained) in the encyclopedia →

Identify your own rocks.

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

App Store Google Play

Physical properties

Formation & geological history

Formed from the recrystallization of silica in sedimentary environments, often through the accumulation of siliceous skeletal remains (diatoms/radiolarians) or precipitation from groundwater. Age varies from Precambrian to modern.

Uses & applications

Historically used for making stone tools (arrowheads/scrapers) due to its sharp edges; and currently used as road aggregate, in landscaping, and as a collector's specimen.

Geological facts

Chert possesses a conchoidal fracture, allowing it to break into razor-sharp edges. It is chemically identical to quartz but with a much finer crystal structure that makes it look opaque or waxy.

Field identification & locations

Identify in the field by its smooth, waxy feel and shell-like (conchoidal) breaking patterns. It will easily scratch glass. Commonly found in limestone or dolomite beds as nodules or layers.