sedimentary
Conglomerate (or Breccia)
Clastic Sedimentary Rock (Conglomeratic)
Hardness: Variable based on matrix and clasts (typically 3-7 Mohs); Color: Tan/brown matrix with dark grey angular clasts; Luster: Dull or earthy; Structure: Clastic, poorly sorted; Specific Gravity: 2.3–2.6.
- Hardness
- Variable based on matrix and clasts (typically 3-7 Mohs)
- Color
- Tan/brown matrix with dark grey angular clasts
- Luster
- Dull or earthy
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Physical properties
Hardness: Variable based on matrix and clasts (typically 3-7 Mohs); Color: Tan/brown matrix with dark grey angular clasts; Luster: Dull or earthy; Structure: Clastic, poorly sorted; Specific Gravity: 2.3–2.6.
Formation & geological history
Formed through the lithification of coarse-grained sediments. In this specimen, the angularity of the dark clasts suggests it is closer to a Breccia, indicating the sediments didn't travel far from their source before being cemented by fine-grained minerals.
Uses & applications
Used primarily in the construction industry as fill material, road base, or decorative stone in landscaping. Occasionally used as a building stone if the cementing matrix is strong.
Geological facts
Sedimentary rocks like these are 'time capsules' because the individual clasts (the dark rocks inside) are actually older than the conglomerate rock itself. Most found on the surface today formed within the last 500 million years.
Field identification & locations
Identify in the field by looking for 'concrete-like' appearance where large pebbles or rock fragments are stuck together by a finer paste. Found in riverbeds, glacial deposits, and alluvial fans.
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