sedimentary

Breccia

Breccia (Clastic Sedimentary Rock)

Hardness: 3-7 (depending on clast composition); Color: Tan, brown, gray, or multi-colored; Luster: Dull to earthy; Crystal structure: Clastic (non-crystalline matrix); Cleavage: None (fractures across clasts); Specific Gravity: 2.3-2.8

Hardness: 3-7 (depending on clast composition)
Color: Tan, brown, gray, or multi-colored
Luster: Dull to earthy

Identified June 30, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of large, angular fragments (clasts) that are cemented together by a fine-grained matrix. These fragments have not been rounded by water transport, suggesting they formed near their source via rockfalls, landslides, or tectonic faulting.

Uses & applications

Primarily used as a decorative architectural stone, for road base, fill material, and occasionally as a gemstone when it contains colorful minerals like agate or jasper.

Geological facts

Unlike conglomerate rocks which have rounded pebbles, breccia fragments remain sharp and angular. Impact breccia can form during meteor strikes, and fault breccia forms during the movement of tectonic plates.

Field identification & locations

Identify by looking for angular, broken rock fragments larger than 2mm embedded in a finer matrix. It is commonly found at the base of cliffs, in alluvial fans, or near fault zones.