sedimentary

Chert (likely flint)

Microcrystalline quartz, SiO₂

AI-generated identification · may be incorrect

Cream to pale gray, dull to waxy luster, with irregular curved surfaces and sharp edges typical of conchoidal fracture. Hardness about 7 Mohs; no cleavage; crystals are microscopic, and specific gravity is about 2.6.

Identified October 8, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms when silica accumulates or replaces material in sedimentary rocks, commonly limestone; its age depends on the host formation. The specimen’s exact age and locality cannot be determined from the image.

Uses & applications

Chert has been used for tools and striking fire; attractive pieces are collected, and some varieties are cut or polished for ornaments.

Geological facts

Flint is a dark or pale variety of chert, and both can fracture into sharp, useful flakes.

Field identification & locations

Look for a very hard, fine-grained texture and smooth, curved fracture surfaces; it commonly occurs in sedimentary beds and nodules. The pale color alone is not enough to distinguish it from other silica-rich rocks.