sedimentary
Chert Breccia
Brecciated Chert
Hardness: 7 (Mohs), Color: Tan, brown, gray, Luster: Dull to waxy, Structure: Clastic with angular fragments, Cleavage: None (conchoidal fracture on fragments)
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Physical properties
Hardness: 7 (Mohs), Color: Tan, brown, gray, Luster: Dull to waxy, Structure: Clastic with angular fragments, Cleavage: None (conchoidal fracture on fragments)
Formation & geological history
Formed through the mechanical breakdown of chert beds followed by rapid deposition and lithification in a fine-grained matrix. Often occurs in fault zones or high-energy sedimentary environments.
Uses & applications
Primarily of geological interest to collectors; historically used for stone tools if the fragments are large enough; occasionally used in decorative landscaping.
Geological facts
Breccia is distinguished from conglomerate by the angularity of its pieces, indicating that the fragments did not travel far after breaking before being cemented.
Field identification & locations
Identify by looking for sharp, angular rock fragments (clasts) fused together in a finer-grained matrix. Commonly found in rocky outcrops and riverbeds near ancient sedimentary basins.
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