sedimentary

Chert (Jasper/Flint variety)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: reddish-brown, tan, and grey banding; Luster: dull to waxy; Structure: cryptocrystalline; Breakage: conchoidal fracture.

Hardness: 7 on Mohs scale
Color: reddish-brown, tan, and grey banding
Luster: dull to waxy

Identified July 2, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale; Color: reddish-brown, tan, and grey banding; Luster: dull to waxy; Structure: cryptocrystalline; Breakage: conchoidal fracture.

Formation & geological history

Formed via the accumulation of silica-rich microfossils (like radiolaria or diatoms) or chemical precipitation from hydrothermal fluids in sedimentary environments. Common in limestone and chalk beds.

Uses & applications

Historically used for stone tools (arrowheads, scrapers) due to its sharp edges. Modernly used as decorative stone, in lapidary work, and as a component in road construction.

Geological facts

Chert has been used by humans for over 2 million years. Its ability to produce sparks when struck against steel made it essential for flintlock firearms and fire-starting.

Field identification & locations

Identify in the field by its smooth, shell-like (conchoidal) fracture surfaces and its ability to scratch glass. Commonly found as nodules or layers within sedimentary rock formations.