sedimentary

Red Chert (Jasper)

Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5–7 (Mohs scale); Color: Red/orange (due to iron inclusions); Luster: Dull to waxy; Crystal structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6 - 2.8

Hardness: 6
Color: Red/orange (due to iron inclusions)
Luster: Dull to waxy

Identified April 11, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like radiolaria) or chemical precipitation from sea water. Often found in seafloor deposits that have been tectonically plates; ages can range from Precambrian to Cenozoic.

Uses & applications

Used historically for stone tools due to sharp edges; currently used for jewelry (lapidary), as a decorative garden stone, and as a collectible gemstone.

Geological facts

Red chert is often specifically called Jasper. It breaks with a conchoidal fracture, creating very sharp edges, which is why it was highly prized by indigenous peoples for arrowheads and scrapers.

Field identification & locations

Identify in the field by its hardness (cannot be scratched by a steel knife) and its smooth, shell-like (conchoidal) fracture surfaces. Commonly found in riverbeds, glacial tills, and coastal outcrops.