sedimentary

Breccia

Clastic Breccia (General mineral composition depends on fragments, often SiO2 or CaCO3)

Hardness: variable (3-7 Mohs); Color: Multi-colored with gray, tan, and dark matrix; Luster: Dull/Earthy; Crystal Structure: Clastic; Cleavage: None (fractures irregularly); Specific gravity: 2.3–2.8.

Hardness: variable (3-7 Mohs)
Color: Multi-colored with gray, tan, and dark matrix
Luster: Dull/Earthy

Identified March 26, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed by the accumulation of angular rock fragments (clasts) that have not been rounded by water transport. These are cemented together by a fine-grained matrix through lithification. Commonly found in fault zones, talus slopes, or impact craters.

Uses & applications

Used primarily as decorative architectural stone, road base, and interior flooring. In the gemstone industry, attractive varieties like 'Mosaic Magnesite' or 'Septarian Breccia' are polished for jewelry or display.

Geological facts

Unlike conglomerate rocks which have rounded edges, breccia fragments are sharp and angular, indicating that the fragments were deposited very close to their source of origin.

Field identification & locations

Identify by looking for 'broken pieces' look: large, sharp-angled chunks embedded in a finer material. Found globally in tectonic regions. For collectors, look for specimens with high color contrast between pieces and matrix.

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