sedimentary

Banded Chert / Chalcedony

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5–7 on Mohs scale; Color: yellowish-tan, cream, gray, and brown banding; Luster: waxy to dull/vitreous; Fracture: conchoidal; Specific Gravity: ~2.65.

Hardness: 6
Color: yellowish-tan, cream, gray, and brown banding
Luster: waxy to dull/vitreous

Identified November 15, 2026More sedimentary →

Explore Banded Chert / Chalcedony in the encyclopedia →

Identify your own rocks.

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

App Store Google Play

Physical properties

Hardness: 6.5–7 on Mohs scale; Color: yellowish-tan, cream, gray, and brown banding; Luster: waxy to dull/vitreous; Fracture: conchoidal; Specific Gravity: ~2.65.

Formation & geological history

Formed through the biochemical or chemical precipitation of silica in marine or lacustrine sedimentary settings, often replacing carbonate minerals or precipitating inside rock cavities over millions of years.

Uses & applications

Historically used by prehistoric peoples for tool and weapon knapping due to its sharp conchoidal fracture. Modern uses include tumbling, lapidary cabochons, aggregate, and decorative landscaping.

Geological facts

Chert and flint are essentially the same mineral variety composed of microcrystalline quartz, but 'flint' typically refers specifically to nodules found in chalk or marly limestone formations.

Field identification & locations

Identify in the field by its hardness (scratches glass/steel easily), smooth waxy feel, and characteristic shell-like conchoidal fracture surfaces. Abundantly found in gravel deposits, riverbeds, and sedimentary limestone outcrops worldwide.