sedimentary

Breccia

Clastic Breccia (SiO2/CaCO3 dominated)

Hardness: 3-7 (depending on clasts); Color: Mottled brown, tan, and dark grey; Luster: Dull/Earthy; Crystal structure: Non-crystalline matrix with angular fragments; Specific gravity: 2.3–2.9.

Hardness: 3-7 (depending on clasts)
Color: Mottled brown, tan, and dark grey
Luster: Dull/Earthy

Identified March 14, 2026More sedimentary →

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Physical properties

Hardness: 3-7 (depending on clasts); Color: Mottled brown, tan, and dark grey; Luster: Dull/Earthy; Crystal structure: Non-crystalline matrix with angular fragments; Specific gravity: 2.3–2.9.

Formation & geological history

Formed through the accumulation of large, angular rock fragments cementation. Often occurs in fault zones, alluvial fans, or debris flows where transport distance was minimal, preventing rounding. Age varies widely by locality.

Uses & applications

Used primarily as road base, construction aggregate, and occasionally as decorative architectural stone or 'ornamental' rock in landscaping.

Geological facts

Unlike conglomerate, which has rounded edges, breccia fragments remain sharp, indicating they did not travel far from their source rock before being buried and lithified.

Field identification & locations

Identify in the field by looking for 'broken' or angular rock chunks larger than 2mm fused together in a finer-grained matrix. Commonly found at the base of cliffs (talus) or near tectonic fault lines.