sedimentary

Chert (Jasper variety)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 on Mohs scale. Color: Brownish-red to tan. Luster: Dull to waxy. Crystal structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific gravity: 2.6-2.7.

Hardness: 6
Color: Brownish-red to tan
Luster: Dull to waxy

Identified July 18, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 on Mohs scale. Color: Brownish-red to tan. Luster: Dull to waxy. 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 or chemical precipitation in sedimentary environments. Common in marine deposits where silica replaces limestone or marrow.

Uses & applications

Historically used for stone tools (flintknapping); currently used in landscaping, tumbling for lapidary use, and as a component in construction aggregate.

Geological facts

Chert has been used by humans for millions of years to create sharp-edged tools like arrowheads and scrapers. Jasper is the name specifically given to opaque, impure varieties of chert often colored by iron oxides.

Field identification & locations

Identified by its extreme hardness (cannot be scratched by a steel knife) and its smooth, shell-like (conchoidal) fracture surfaces. Common in riverbeds and gravel pits.