sedimentary

Chert (Pink variety)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 on Mohs scale; Color: Pink, tan, or reddish; Luster: Waxy to dull; Crystal structure: Cryptocrystalline (microscopic); Cleavage: None (conchoidal fracture); Specific gravity: 2.65.

Hardness: 6
Color: Pink, tan, or reddish
Luster: Waxy to dull

Identified June 21, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 on Mohs scale; Color: Pink, tan, or reddish; Luster: Waxy to dull; Crystal structure: Cryptocrystalline (microscopic); Cleavage: None (conchoidal fracture); Specific gravity: 2.65.

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like radiolarians or diatoms) or by chemical precipitation from silica-rich fluids within other sedimentary rocks like limestone. Common in Paleozoic to Cenozoic strata.

Uses & applications

Historically used for stone tools and weapons due to sharp edges; currently used for landscaping, road ballast, and sometimes as semi-precious gemstones for jewelry (cabochons).

Geological facts

Chert is so hard it can strike sparks from steel, which led to its historical use as 'flint' for starting fires and in flintlock firearms. Pink varieties often get their color from trace amounts of iron oxide.

Field identification & locations

Identify by its 'flint-like' behavior: it breaks with smooth, curved surfaces (conchoidal fracture) and cannot be scratched by a steel knife. Commonly found in riverbeds, gravel pits, and as nodules in limestone outcrops.