sedimentary

Chert Nodules

Microcrystalline Quartz (SiO2)

Hardness: 7 (Mohs scale), Color: Varying shades of grey to brown, Luster: Dull to waxy, Crystal Structure: Cryptocrystalline, Fracture: Conchoidal, Specific Gravity: 2.65

Identified June 14, 2026More sedimentary →

Identify your own rocks.

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

App Store Google Play

Physical properties

Hardness: 7 (Mohs scale), Color: Varying shades of grey to brown, Luster: Dull to waxy, Crystal Structure: Cryptocrystalline, Fracture: Conchoidal, Specific Gravity: 2.65

Formation & geological history

Forms through the precipitation of silica in sedimentary environments, often replacing carbonate material in limestone or chalk beds. It typically forms in marine environments and can range from Paleozoic to Cenozoic in age.

Uses & applications

Historically used for making sharp tools like arrowheads and scrapers. Modern uses include road surfacing, decorative garden stones, and as a component in glass manufacturing.

Geological facts

Flint is a variety of chert. Because of its extreme hardness and conchoidal fracture, it was one of the most important minerals for early humans to create survival tools.

Field identification & locations

Identify in the field by its smooth, almost glass-like fracture surface and its ability to scratch glass. Often found as rounded nodules or irregular masses in limestone outcrops or riverbeds.