sedimentary

Chert (Jasper)

Microcrystalline Quartz (SiO2)

Hardness: 6.5-7 (Mohs scale); Color: Brown, tan, and reddish-orange; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7.

Hardness: 6
Color: Brown, tan, and reddish-orange
Luster: Waxy to dull

Identified June 23, 2026More sedimentary →

Identify your own rocks.

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

App Store Google Play

Physical properties

Hardness: 6.5-7 (Mohs scale); Color: Brown, tan, and reddish-orange; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7.

Formation & geological history

Formed via the accumulation of silica-rich organic remains (like radiolarians) or through chemical precipitation in marine or groundwater environments. This specimen shows oxidation typical of terrestrial weathering.

Uses & applications

Historically used for stone tools (knapping due to sharp edges); currently used in jewelry (cabochons), as landscaping stone, and for lapidary collection.

Geological facts

Chert is so hard it can scratch steel. When struck against steel, it can produce sparks, leading to its historical use in flintlock firearms and fire-starting.

Field identification & locations

Identify by its smooth, waxy texture and conchoidal (shell-like) fracture pattern. Often found in riverbeds or as nodules within limestone. It will not react to acid.