sedimentary

Chert (variations include Flint or Jasper)

Aphanitic Silica (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 (Mohs scale), Color: Gray, brown, or tan with waxy luster, Crystal structure: Microcrystalline/Cryptocrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.65

Identified May 24, 2026More sedimentary →

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Physical properties

Hardness: 7 (Mohs scale), Color: Gray, brown, or tan with waxy luster, Crystal structure: Microcrystalline/Cryptocrystalline, 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 chemical precipitation from groundwater within limestone or chalk beds. Commonly found in Paleozoic and Mesozoic strata.

Uses & applications

Historically used for stone tools and starting fires (flint). Currently used in road construction, as an abrasive, and occasionally for lapidary work.

Geological facts

Because it breaks with a conchoidal fracture, it creates edges thinner than a steel scalpel, making it the primary material for prehistoric arrowheads and knives.

Field identification & locations

Identify in the field by its waxy texture, smooth curved (shell-like) fractures, and its ability to scratch glass. Commonly found in riverbeds or eroding out of limestone cliffs.