sedimentary

Brown chert (flint)

Microcrystalline quartz (SiO₂), commonly called chert; “flint” is a dark variety

AI-generated identification · may be incorrect

Hardness about 7 Mohs; brown to honey-colored with a waxy to glassy luster and no visible crystals or cleavage. Typically dense, with smooth, curved conchoidal fractures; the wet-looking sheen may be from moisture or a polished surface.

Identified October 16, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms when silica-rich material replaces or accumulates in sediment, often in limestone or chalk. Chert occurs in rocks ranging from Precambrian to recent ages; this specimen’s age cannot be determined from the image.

Uses & applications

Used historically for stone tools and fire-starting; attractive pieces are collected or shaped for ornamental objects.

Geological facts

Its sharp conchoidal edges made chert valuable for prehistoric cutting tools.

Field identification & locations

Look for hardness near 7, a glass-like fracture, and resistance to scratching by a steel blade. Chert is common worldwide, especially in sedimentary formations; the image alone cannot confirm the exact variety.