sedimentary

Banded chert (likely an iron-stained chert nodule)

Microcrystalline quartz, SiO₂; chalcedony with iron-oxide staining

AI-generated identification · may be incorrect

Opaque, rounded specimen with tan, cream, and brown bands and a waxy-to-dull surface. Quartz hardness is about 7 Mohs; microcrystalline structure, no visible cleavage, and conchoidal fracture are typical.

Identified October 13, 2026More sedimentary →

Explore Banded chert (likely an iron-stained chert nodule) 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

Silica-rich sediment or replacement silica hardened into chert, with banding and brown iron-oxide staining formed during deposition or later alteration. Such chert forms in many geological ages and sedimentary settings.

Uses & applications

Used historically for tools and fire-starting; attractive pieces are collected or cut and polished for decorative objects and jewelry.

Geological facts

Chert is cryptocrystalline quartz, meaning its crystals are too small to distinguish unaided; banding may reflect changes in silica or impurity content.

Field identification & locations

Look for a hard, fine-grained texture, waxy luster, and curved conchoidal breaks; it commonly occurs as nodules in limestone or other sedimentary rocks. Exact identification is limited from the photo.