sedimentary

Red Chert (Jasper)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 on Mohs scale. Color: Dull red to brownish-red. Luster: Waxy to dull. Crystal Structure: Microcrystalline (Trigonal system). Cleavage: None, exhibits conchoidal (shell-like) fracture. Specific Gravity: 2.58-2.91.

Hardness: 6
Color: Dull red to brownish-red
Luster: Waxy to dull

Identified June 17, 2026More sedimentary →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like radiolaria or diatoms) or chemical precipitation from hydrothermal fluids in marine environments. Often found in nodules within limestone or as bedded deposits.

Uses & applications

Used historically for stone tools and arrowheads due to its sharp edges when fractured. Currently used in lapidary work for cabochons, beads, and as decorative gravel or landscaping stone.

Geological facts

Red chert is often colored by iron oxide (hematite) inclusions. High-quality red chert is frequently referred to as Jasper in the gemstone trade. It was one of the most important minerals for early human technology.

Field identification & locations

Identify in the field by its hardness (will scratch glass), conchoidal fracture pattern, and waxy texture. Frequently found in riverbeds, glacial tills, and sedimentary outcrops particularly in the Midwestern and Western United States.