sedimentary

Chert (Yellow Jasper)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 on Mohs scale; Color: Opaque yellow to mustard brown; Luster: Dull to waxy; Structure: Cryptocrystalline; Cleavage: None (Conchoidal fracture); Specific Gravity: 2.6-2.7.

Hardness: 6
Color: Opaque yellow to mustard brown
Luster: Dull to waxy

Identified June 27, 2026More sedimentary →

Explore Chert (Yellow Jasper) 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: Opaque yellow to mustard brown; Luster: Dull to waxy; Structure: Cryptocrystalline; Cleavage: None (Conchoidal fracture); Specific Gravity: 2.6-2.7.

Formation & geological history

Formed from the accumulation of silica-rich organic remains or chemical precipitation in sedimentary environments. The yellow color is caused by the presence of iron oxide (goethite) inclusions.

Uses & applications

Historically used for making stone tools due to its sharp edges; currently used for lapidary work, jewelry (cabochons), and as a decorative landscaping rock.

Geological facts

Chert and Jasper are essentially the same material, with the name 'Jasper' usually reserved for colorful, opaque varieties. It was one of the most important minerals for early humans to create fire-starting kits and arrowheads.

Field identification & locations

Identify by its smooth, waxy surface and shell-like (conchoidal) fracture pattern where broken. Commonly found in riverbeds, beaches, and sedimentary basins worldwide.