sedimentary

Chert (Iron-stained)

Chert (Silicon Dioxide, SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: tan to brown (iron-stained); Luster: dull to waxy; Structure: microcrystalline (no visible grains); Cleavage: none (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 on Mohs scale
Color: tan to brown (iron-stained)
Luster: dull to waxy

Identified May 24, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale; Color: tan to brown (iron-stained); Luster: dull to waxy; Structure: microcrystalline (no visible grains); Cleavage: none (conchoidal fracture); Specific Gravity: 2.65

Formation & geological history

Formed by the accumulation of siliceous remains of organisms (like diatoms) or by chemical precipitation from silica-rich fluids in sedimentary basins. Often found as nodules in limestone or chalk.

Uses & applications

Historically used for making stone tools (arrowheads). Industrially used in road construction as aggregate and as a low-cost lapidary material.

Geological facts

Chert is extremely durable and chemically stable. Due to its sharpness when fractured, it was one of the most important minerals for early humans in creating survival tools.

Field identification & locations

Identify in the field by its hardness (it will scratch glass) and its curved, shell-like (conchoidal) fracture pattern. It is common in riverbeds and limestone outcrops globally.