sedimentary

Chert (Quartz-rich)

Microcrystalline Silica (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 (Mohs scale), Color: Tan, brown, and cream with slight iron staining. Luster: Dull to waxy. Structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific Gravity: Approximately 2.6.

Color: Tan, brown, and cream with slight iron staining
Luster: Dull to waxy

Identified July 5, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich micro-organisms or chemical precipitation in marine environments. Often found as nodules in limestone or dolomite. Geologically common from Pre-Cambrian to present.

Uses & applications

Historically used for stone tools (knapping) due to its sharp edges. Currently used in road aggregate, aquarium decor, and occasionally as high-quality lapidary material.

Geological facts

Chert was one of the most important minerals for early humans, used to create arrowheads, scrapers, and fire-starting tools. It is highly resistant to chemical weathering.

Field identification & locations

Identify in the field by its superior hardness (scratches glass) and shell-like (conchoidal) fracture pattern when broken. It often feels denser and smoother than surrounding limestone.