sedimentary

Chert (Jasper)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Reddish-brown to maroon; Luster: Waxy to dull; Crystal structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7

Hardness: 6
Color: Reddish-brown to maroon
Luster: Waxy to dull

Identified June 7, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from the accumulation of silica-rich microfossils (like radiolarians) or chemical precipitation in marine environments, often undergoing diagenesis over millions of years.

Uses & applications

Historically used for stone tools (arrowheads); currently used in jewelry (as jasper), aquarium gravel, and road construction material.

Geological facts

The reddish color is typically caused by iron oxide inclusions. It was one of the most important minerals for early humans due to its ability to hold a sharp edge when fractured.

Field identification & locations

Identify by its 'flint-like' waxy texture, smooth conchoidal (shell-like) fracture patterns, and its ability to scratch glass. Commonly found in riverbeds or as nodules in limestone.