sedimentary

Polygenetic Conglomerate (or Breccia)

Clastic Sedimentary Rock

Hardness: variable (matrix 3-5, clasts up to 7); Color: grey or brownish matrix with dark grey to black clasts; Luster: dull to earthy; Structure: clastic texture with angular to sub-rounded fragments; Cleavage: none; Specific Gravity: 2.5-2.8

Hardness: variable (matrix 3-5, clasts up to 7)
Color: grey or brownish matrix with dark grey to black clasts
Luster: dull to earthy

Identified June 17, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the lithification of coarse sedimentary fragments. These fragments typically accumulate in high-energy environments like alluvial fans, riverbeds, or glacial deposits. The dark clasts are often limestone or chert embedded in a finer sandy or calcareous matrix.

Uses & applications

Primarily used as aggregate in construction, road base material, or as a decorative stone in landscaping and architectural facades.

Geological facts

This specimen shows features of an 'intraformational' rock, where the fragments are similar in compostion to the matrix but formed from slightly older deposits that were broken up and redeposited nearby.

Field identification & locations

Identify in the field by looking for large, visible rock fragments (clasts) cemented together by a finer-grained matrix. Commonly found in tectonic basins or mountain foothills. For collectors, look for high contrast between matrix and clasts.

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