sedimentary

Brecciated Chert

Silicon Dioxide (SiO2)

Hardness: 7 (Mohs scale); Color: White matrix with brown/tan angular clasts; Luster: Waxy to dull; Crystal structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Hardness: 7 (Mohs scale)
Color: White matrix with brown/tan angular clasts
Luster: Waxy to dull

Identified June 28, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the mechanical breaking of chert beds followed by chemical cementation by silica-rich fluids. Often associated with tectonic activity or karst collapse in limestone/dolostone environments.

Uses & applications

Used in landscaping, as a lapidary material for cabochons, and historically by indigenous peoples for stone tools due to its sharp conchoidal fracture.

Geological facts

Breccia comes from the Italian word for 'rubble' or 'loose gravel'. Chert is one of the most durable sedimentary rocks and can preserve microfossils in extreme detail.

Field identification & locations

Identify in the field by its high hardness (cannot be scratched by a steel knife), angular fragments embedded in a fine-grained matrix, and waxy luster. Common in areas with ancient limestone deposits.