sedimentary

Red Chert (Jasper)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 Mohs; Color: Opaque reddish-brown; Luster: Dull to waxy; Structure: Microcrystalline; Cleavage: None (conchoidal fracture).

Hardness: 6
Color: Opaque reddish-brown
Luster: Dull to waxy

Identified July 2, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 Mohs; Color: Opaque reddish-brown; Luster: Dull to waxy; Structure: Microcrystalline; Cleavage: None (conchoidal fracture).

Formation & geological history

Formed from the accumulation of silica-rich microfossils (like radiolaria) or chemical precipitation in marine environments, often associated with iron impurities that provide the red color.

Uses & applications

Used historically for stone tools and weapons (due to sharp edges upon fracturing); currently used in jewelry (cabochons), landscaping, and as a collector specimen.

Geological facts

Chert is so hard it can scratch steel. Red varieties are often referred to as Jasper, especially when they take a high polish. It was one of the most important minerals for prehistoric humans to create arrowheads.

Field identification & locations

Identify by its 'flint-like' waxy texture, smooth curved (conchoidal) fractures, and its inability to be scratched by a steel knife. Common in riverbeds and sedimentary outcrops.