sedimentary

Chert (Red Jasper variant)

Microcrystalline Quartz (SiO2)

Hardness: 6.5–7 on Mohs scale. Color: Reddish-brown to pink (due to iron oxide inclusions). Luster: Waxy to dull. Crystal structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific gravity: 2.6–2.7.

Hardness: 6
Color: Reddish-brown to pink (due to iron oxide inclusions)
Luster: Waxy to dull

Identified February 14, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from the accumulation of silica-rich organic remains (like radiolaria or diatoms) or through chemical precipitation from hydrothermal fluids. It often occurs as nodules or layers within limestone and chalk beds across various geological periods.

Uses & applications

Historically used for stone tools (arrowheads, scrapers) due to its sharp edges. Modern uses include jewelry (cabochons), interior decoration, and as a component in construction aggregates.

Geological facts

Because it breaks with a conchoidal fracture, it was one of the most important minerals for early humans to create survival tools. Red chert specifically gets its color from oxidized iron, essentially mineral 'rust' trapped in the silica lattice.

Field identification & locations

Identify in the field by its smooth, shell-like fracture surfaces and its ability to scratch glass. It will produce sparks when struck against steel. Commonly found in riverbeds, desert pavements, and exposed limestone strata.

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