sedimentary

Red Chert (Jasper)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs scale); Color: Red, reddish-brown; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.58-2.91

Hardness: 6
Color: Red, reddish-brown
Luster: Waxy to dull

Identified February 21, 2026More sedimentary →

Explore Red Chert (Jasper) in the encyclopedia →

Identify your own rocks.

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

App Store Google Play

Physical properties

Hardness: 6.5-7 (Mohs scale); Color: Red, reddish-brown; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.58-2.91

Formation & geological history

Formed from the accumulation of silica-rich organic remains (like radiolarians) or chemical precipitation from hydrothermal fluids in marine environments. Red coloring comes from iron oxide inclusions.

Uses & applications

Used primarily for lapidary work (jewelry, cabochons), ornamental stone, and historically for stone tools due to its sharp conchoidal fracture.

Geological facts

In antiquity, red chert was often used to create spear points and knives because of its extreme hardness and ability to hold a razor-sharp edge. It is a common constituent of 'banded iron formations'.

Field identification & locations

Identify in the field by its smooth, shell-like (conchoidal) fracture surfaces and its inability to be scratched by a steel knife. Commonly found in riverbeds or as nodules in limestone/dolomite.