sedimentary

Chert (Jasper)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 (Mohs); Color: Reddish-brown, yellow-green variegated; Luster: Waxy to vitreous; Crystal structure: Trigonal/Microcrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.58-2.91

Hardness: 6
Color: Reddish-brown, yellow-green variegated
Luster: Waxy to vitreous

Identified June 22, 2026More sedimentary →

Identify your own rocks.

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

App Store Google Play

Physical properties

Formation & geological history

Forms from the accumulation of silica-rich organic remains (like diatoms or radiolarians) or through the chemical precipitation of silica in sedimentary basins and limestone cavities.

Uses & applications

Historically used for making stone tools; currently used in jewelry (cabochons), as an abrasive, and in landscaping or as a collectible gemstone.

Geological facts

Jasper is a variety of chert colored by iron impurities. It was used by ancient civilizations for seal stones and amulets due to its durability and color variety.

Field identification & locations

Identify by its waxy appearance and smooth, shell-like (conchoidal) fracture surface. It will scratch glass but cannot be scratched by a steel knife. Common in riverbeds and sedimentary outcrops.