sedimentary

Chert Breccia

Brecciated Chert (Microcrystalline SiO2)

AI-generated identification · may be incorrect

Hardness: 7 (Mohs); Color: Tan, brown, and grey clasts in a dark matrix; Luster: Waxy to dull (wet in image); Structure: Angular fragments; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 (Mohs)
Color: Tan, brown, and grey clasts in a dark matrix
Luster: Waxy to dull (wet in image)

Identified July 9, 2026More sedimentary →

Explore Chert Breccia in the encyclopedia →

Identify your own rocks.

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

App Store Google Play

Physical properties

Formation & geological history

Formed when existing chert or jasper layers are broken by tectonic movement (faulting) and then re-cemented by silica-rich fluids. Likely from the geological complexes near Yucca Valley and Joshua Tree, CA.

Uses & applications

Used primarily as decorative landscaping stone, lapidary material for tumbling/cabbing, and historically by indigenous peoples for tool making due to its sharp edges.

Geological facts

The location provided (near Yucca Valley, CA) is situated near the Pinto Mountain Fault, a region known for tectonic activity that creates brecciated rocks exactly like this specimen.

Field identification & locations

Identify in the field by its extreme hardness (cannot be scratched by a steel knife) and the angular, broken appearance of the 'stones within the stone.' Common in Mojave Desert alluvial washes.