sedimentary
Breccia
Breccia (Clastic sedimentary rock)
Hardness: 6-7 (if silica-rich matrix); Color: Mixed greys, tans, and browns; Luster: Dull/Earthy; Structure: Clastic with angular fragments over 2mm; Cleavage: None
- Hardness
- 6-7 (if silica-rich matrix)
- Color
- Mixed greys, tans, and browns
- Luster
- Dull/Earthy
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Physical properties
Hardness: 6-7 (if silica-rich matrix); Color: Mixed greys, tans, and browns; Luster: Dull/Earthy; Structure: Clastic with angular fragments over 2mm; Cleavage: None
Formation & geological history
Forms from the accumulation of large, angular rock fragments. The angularity indicates the fragments haven't traveled far from their source, often forming at the base of talus slopes, via tectonic faulting, or during volcanic eruptions.
Uses & applications
Mainly used as architectural stone for interior walls, floor tiles, and as decorative gravel. Historically used for columns and statues.
Geological facts
The word 'breccia' comes from the Italian meaning 'loose gravel' or 'broken stone'. It is distinct from conglomerate rock, which contains rounded fragments.
Field identification & locations
Look for a concrete-like appearance but with sharp, angular stones embedded in a finer-grained matrix. Found along fault zones and cliff bases globally.
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