sedimentary

Chert Geode Nodules

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 (Mohs scale), Color: tan, grey, or white exterior with possible crystalline interior. Luster: dull to waxy. Structure: nodular/spherical. Cleavage: none (conchoidal fracture).

Luster: dull to waxy

Identified July 2, 2026More sedimentary →

Explore Chert Geode Nodules 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 (Mohs scale), Color: tan, grey, or white exterior with possible crystalline interior. Luster: dull to waxy. Structure: nodular/spherical. Cleavage: none (conchoidal fracture).

Formation & geological history

Formed via chemical precipitation of silica-rich fluids within cavities of sedimentary rocks like limestone or dolomite, often during diagenesis.

Uses & applications

Primarily collected by rockhounds as lapidary material; larger specimens may be cracked open to reveal crystals. Historically used for stone tools due to its hardness.

Geological facts

Geodes are often indistinguishable from ordinary stones on the outside. The only way to know if they are hollow or contain crystals is to break them or saw them in half.

Field identification & locations

Found in riverbeds, limestone quarries, and desert environments. Identify by their rounded, lumpy, or cauliflower-like exterior texture and high density compared to similar-looking rocks.