sedimentary
Conglomerate
Clastic sedimentary rock (Polymictic Conglomerate)
Hardness: Variable (based on parent rocks); Color: Multi-colored clasts in a reddish-brown or sandy matrix; Luster: Dull/Earthy; Structure: Clastic with rounded grains >2mm; Specific Gravity: Approx 2.6-2.9
- Hardness
- Variable (based on parent rocks)
- Color
- Multi-colored clasts in a reddish-brown or sandy matrix
- Luster
- Dull/Earthy
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Physical properties
Hardness: Variable (based on parent rocks); Color: Multi-colored clasts in a reddish-brown or sandy matrix; Luster: Dull/Earthy; Structure: Clastic with rounded grains >2mm; Specific Gravity: Approx 2.6-2.9
Formation & geological history
Formed through the lithification of rounded gravel and boulders. Rounded shapes indicate transport by high-energy water (rivers or beaches). Found in ancient riverbeds and alluvial fans throughout geological time.
Uses & applications
Commonly used as a coarse aggregate in the construction industry for roads and concrete. Occasional use as ornamental stone or for building facings.
Geological facts
Conglomerate is often called 'puddingstone' because it looks like raisins in a pudding. Similar rocks with sharp, angular fragments are called breccia instead of conglomerate.
Field identification & locations
Identify in the field by looking for large, rounded clasts (stones) cemented together by a finer-grained matrix. Found in sedimentary basins and mountain ranges globally.
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