sedimentary

Yellow-brown flint or chert

Microcrystalline quartz (SiO₂), commonly with iron-oxide impurities

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; opaque honey-brown color, waxy to dull luster, very fine-grained cryptocrystalline structure, and no visible cleavage. It typically breaks with smooth conchoidal fractures and may show pale weathering lines or cortex.

Identified August 25, 2026More sedimentary →

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Physical properties

Formation & geological history

Chert forms when silica replaces or precipitates within marine or freshwater sediments, often from microscopic silica-rich organisms; its age varies from Precambrian to recent. The shape appears naturally weathered or possibly tumbled/polished.

Uses & applications

Used historically for sharp tools and fire-starting, and today for lapidary objects, décor, and collections; it is generally not a high-value gemstone.

Geological facts

Flint is commonly considered a dark, knappable variety of chert, while iron oxides produce yellow, orange, and brown colors. A steel file should make little or no mark, and quartz-rich chert can scratch ordinary glass.

Field identification & locations

Common in limestone, chalk, river gravels, and glacial deposits worldwide, especially England, France, the Great Lakes region, and parts of Texas. Confirm with a glass-scratch test and conchoidal fracture; avoid confusing it with amber or resin.