sedimentary

Chert (Flint)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 Mohs scale; Color: typically gray, white, or beige; Luster: waxy to dull; Structure: microcrystalline; Cleavage: none, exhibits conchoidal fracture; Specific gravity: approx. 2.65.

Hardness: 7 Mohs scale
Color: typically gray, white, or beige
Luster: waxy to dull

Identified June 27, 2026More sedimentary →

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Physical properties

Hardness: 7 Mohs scale; Color: typically gray, white, or beige; Luster: waxy to dull; Structure: microcrystalline; Cleavage: none, exhibits conchoidal fracture; Specific gravity: approx. 2.65.

Formation & geological history

Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine or freshwater environments. Most specimens are millions of years old, often found in limestone or chalk beds.

Uses & applications

Historically used for stone tools/weapons; modernly used as road aggregate, architectural stone, and in spark-lighting mechanisms (flint).

Geological facts

Chert has been used by humans for over 2 million years to create sharp-edged tools because of its predictable fracture pattern. Some banded varieties are sold as decorative river rocks.

Field identification & locations

Identify in the field by its hardness (scratches glass), waxy appearance, and very sharp, curved (conchoidal) edges when broken. Commonly found in stream beds or eroded from limestone outcrops.