sedimentary

Breccia Pebble

Sedimentary Breccia

Hardness: 6-7 (Mohs scale), Color: Variegated grays, tans, and browns with a salt-and-pepper appearance, Luster: Dull to sub-vitreous, Structure: Clastic with angular fragments, Cleavage: None (conchoidal fracture on quartz parts)

Identified June 28, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed by the accumulation of angular rock fragments and mineral grains cemented together by a fine-grained matrix. The angularity suggests the fragments have not traveled far from their source, likely originating from mechanical weathering or tectonic activity.

Uses & applications

Larger deposits are used for construction aggregate and road base. Polished pebbles are popular for landscaping, aquarium decor, and amateur rock collecting.

Geological facts

Breccia is distinguished from conglomerate by the shape of its fragments; while conglomerates contain rounded clasts, breccia is composed of sharp, angular pieces. Common locations include fault zones, alluvial fans, and the base of cliffs.

Field identification & locations

Identify in the field by looking for a 'mosaic' or 'jigsaw' appearance of sharp rock chunks stuck within a finer silt or clay material. This specific specimen has been water-worn into a smooth pebble shape, masking its typical jagged exterior.