sedimentary

Chert (Jasper-bearing)

Chert (Silicon Dioxide, SiO2)

AI-generated identification · may be incorrect

Hardness: 7 (Mohs scale); Color: Variegated greens, grays, and reddish-browns (iron-stained); Luster: Waxy to dull (on weathered surfaces); Crystal structure: Microcrystalline/cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6 – 2.7.

Hardness: 7 (Mohs scale)
Color: Variegated greens, grays, and reddish-browns (iron-stained)
Luster: Waxy to dull (on weathered surfaces)

Identified April 12, 2026More sedimentary →

Explore Chert (Jasper-bearing) 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

Formed through the accumulation of silica-rich organic remains (like diatoms or radiolarians) or chemical precipitation from groundwater. This specimen appears weathered and may have been part of a larger formation dating from the Precambrian to Cenozoic eras.

Uses & applications

Historically used for stone tools (arrowheads/scrapers) due to conchoidal fracture. Modern uses include landscaping, construction aggregate, and lapidary work (when colorful like Jasper).

Geological facts

Chert is so durable that it often remains as 'residual' rock after surrounding limestone has weathered away. The reddish patches in this specimen are likely Jasper, a variety of chert colored by iron impurities.

Field identification & locations

Identify by its extreme hardness (scratches glass), waxy feel on fresh breaks, and curved 'conchoidal' fracture patterns. Common globally in sedimentary basins. Look for it in riverbeds or as 'nodules' in limestone outcrops.