sedimentary

Flint (chert)

Microcrystalline quartz (SiO₂), commonly called chert or flint

AI-generated identification · may be incorrect

Gray, opaque, with a waxy-to-dull luster and conchoidal fracture; hardness about 7 Mohs, no cleavage, and trigonal quartz structure at the microscopic scale. The image shows a small, chipped-looking piece; exact identification from appearance alone is uncertain.

Identified October 4, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms when silica accumulates or replaces material in sedimentary rocks, often limestone or chalk. It may range from ancient to geologically recent, depending on its host deposits.

Uses & applications

Historically used for stone tools and fire-starting; today collected and sometimes used decoratively.

Geological facts

Sharp conchoidal edges made flint valuable for prehistoric blades and points.

Field identification & locations

Look for hardness near 7, a smooth curved fracture surface, and edges that can be very sharp; common in chalk and limestone regions. The pictured piece appears consistent with gray flint, though similar-looking silica-rich rocks can occur.