sedimentary
Limestone Breccia
Sedimentary Breccia (Calcareous)
Hardness: 3-4 (Mohs); Color: Gray, tan, or white with earthy matrix; Luster: Dull/Earthy; Crystal structure: Non-crystalline matrix with angular clasts; Cleavage: None (fractures around clasts); Specific gravity: 2.3-2.7
- Hardness
- 3-4 (Mohs)
- Color
- Gray, tan, or white with earthy matrix
- Luster
- Dull/Earthy
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Physical properties
Hardness: 3-4 (Mohs); Color: Gray, tan, or white with earthy matrix; Luster: Dull/Earthy; Crystal structure: Non-crystalline matrix with angular clasts; Cleavage: None (fractures around clasts); Specific gravity: 2.3-2.7
Formation & geological history
Formed by the mechanical breakdown of limestone followed by rapid burial and cementation. Often occurs along fault zones, at the base of cliffs (talus), or in alluvial fans where there is little transport time to round the fragments.
Uses & applications
Used primarily in construction as road base, aggregate, and as a decorative stone in landscaping. Can sometimes be used in the production of cement.
Geological facts
Breccia is distinguished from conglomerate by the angularity of its pieces; angular pieces suggest the rock has not traveled far from its source. If the matrix is harder than the clasts, it can be polished for architectural use.
Field identification & locations
Identify by looking for sharp, jagged rock fragments fused together by a finer-grained mineral 'glue'. In the field, it will often fizz when touching weak hydrochloric acid due to the calcium carbonate content.
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