sedimentary

Chert (varieties: Flint, Jasper)

Silicon Dioxide (SiO2) - Cryptocrystalline Quartz

AI-generated identification · may be incorrect

Hardness: 7 (Mohs scale); Color: Gray, tan, brown, or white; Luster: Waxy to dull; Breakage: Conchoidal fracture (curved surfaces); Structure: Cryptocrystalline; Specific Gravity: 2.65

Hardness: 7 (Mohs scale)
Color: Gray, tan, brown, or white
Luster: Waxy to dull

Identified July 2, 2026More sedimentary →

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Physical properties

Hardness: 7 (Mohs scale); Color: Gray, tan, brown, or white; Luster: Waxy to dull; Breakage: Conchoidal fracture (curved surfaces); Structure: Cryptocrystalline; Specific Gravity: 2.65

Formation & geological history

Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine environments. Often found as nodules within limestone or chalk beds.

Uses & applications

Historically used for making stone tools (arrowheads, knives) due to its sharp edges; used as flint for sparks; currently used in industrial abrasives and road construction.

Geological facts

Chert is so hard it can scratch steel. It is one of the most durable rocks on Earth, often surviving long after the surrounding limestone has eroded away. Flint is a specific dark variety of chert commonly found in chalk.

Field identification & locations

Identify in the field by its waxy texture and shell-like (conchoidal) fractures. It will not react with acid, unlike the limestone it is often found in. Common in gravel beds and mountain outcrops.