sedimentary

Chert nodule in sandstone or iron-stained host rock

Microcrystalline quartz (SiO₂), likely chert/flint

AI-generated identification · may be incorrect

Hardness about 7 Mohs; gray to bluish-gray, opaque, waxy to dull luster, with conchoidal fracture. The surrounding tan-orange matrix appears porous and iron-stained, probably sandstone or weathered sediment.

Identified September 9, 2026More sedimentary →

Explore Chert nodule in sandstone or iron-stained host rock 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

Chert forms when silica-rich groundwater, biogenic silica, or volcanic ash replaces or cements sediment, commonly during diagenesis; the exact age cannot be determined from the image. The angular gray core may also represent a silicified clast or breccia fragment.

Uses & applications

Common chert is used for aggregate, road material, and historically tools and fire-starting; attractive pieces are collected but are rarely used as gemstones.

Geological facts

Its sharp conchoidal edges and glassy fracture distinguish it from most sandstone. The tan matrix and gray silica-rich center suggest silicification or a chert-bearing conglomeratic/brecciated rock.

Field identification & locations

Look for scratch resistance against glass, no visible cleavage, and a sharp curved fracture; a steel nail usually will not scratch fresh chert. Common in sedimentary terrains worldwide, especially limestone, chalk, and conglomerate regions.