sedimentary

Chert (Yellow Jasper/Flint)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7.0 (Mohs scale); Color: Yellow-brown, olive, tan; Luster: Waxy to dull (glassy when wet); Structure: Microcrystalline; Cleavage: None (conchoidal fracture).

Hardness: 6
Color: Yellow-brown, olive, tan
Luster: Waxy to dull (glassy when wet)

Identified June 19, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7.0 (Mohs scale); Color: Yellow-brown, olive, tan; Luster: Waxy to dull (glassy when wet); Structure: Microcrystalline; Cleavage: None (conchoidal fracture).

Formation & geological history

Formed by the precipitation of silica from groundwater or within sedimentary basins. Often found as nodules in limestone or chalk beds. It can be millions of years old, originating from the Paleozoic to Cenozoic eras.

Uses & applications

Historically used for stone tools and fire-starting (flint). Currently used in landscaping, as tumbling rough for lapidary work, and for decorative gravel.

Geological facts

Chert is so hard that it can scratch steel. When broken, it produces sharp, curved edges called conchoidal fractures, which made it the primary material for prehistoric arrowheads.

Field identification & locations

Identify in the field by its smooth, waxy texture and sharp, shell-like edges where broken. It will not be scratched by a steel knife. Commonly found in riverbeds or coastal erosion zones.