Sedimentary Breccia

Physical Properties

Hardness: 3-7 (variable based on clasts/matrix); Color: Tan, beige, grey, or reddish; Luster: Dull/Earthy; Structure: Clastic (angular fragments); Cleavage: None; Specific Gravity: 2.3–2.6.

Formation & Geological History

Formed by the accumulation of large angular rock fragments that have not been rounded by water transport. They are often created by tectonic movement, landslides, or talus accumulation and later lithified by mineral cementation.

Uses & Applications

Used primarily as architectural stone, base material for roads, or as an ornamental stone in building facades. High-quality specimens are kept as geological study samples.

Geological Facts

Unlike conglomerate rocks, which have rounded fragments, breccia's angular fragments indicate that the source material was moved only a very short distance from its origin before being buried.

Field Identification & Locations

Identify in the field by looking for large, sharp-edged 'clasts' (broken pieces) cemented within a finer-grained material. Often found at the base of cliffs or along fault zones. Reacting to dilute HCl can identify a calcite matrix.

Identified on: 4/25/2026

Mode: Standard