sedimentary

Chert (varieties: Flint or Jasper)

Silicon dioxide (SiO2) / Microcrystalline Quartz

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: Tan, brown, white with dark interior; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Opaque.

Hardness: 7 on Mohs scale
Color: Tan, brown, white with dark interior
Luster: Waxy to dull

Identified July 9, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale; Color: Tan, brown, white with dark interior; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Opaque.

Formation & geological history

Formed by the precipitation of silica in sedimentary environments, often from the remains of siliceous organisms like diatoms or radiolarians. Commonly found as nodules in limestone or chalk beds.

Uses & applications

Historically used for making stone tools (arrowheads, scrapers) due to its sharp edges; current uses include road surfacing, decorative landscaping, and as a component in glass manufacturing.

Geological facts

Chert has a conchoidal fracture, allowing it to break into sharp curved edges. This property made it the primary material for prehistoric survival tools and weapons for millions of years.

Field identification & locations

Look for a waxy texture and shell-like (conchoidal) fracture patterns when broken. It is harder than steel and will scratch glass. Found globally, especially in limestone-rich regions.