Conglomerate
“Nature's concrete”
Sedimentary
Conglomerate is a coarse-grained sedimentary rock made of rounded gravel and pebbles cemented together by finer material. Each pebble tells a story about its source rock and the river or ocean that tumbled it smooth before deposition.
Composition
variable clasts of quartz, feldspar, rock fragments, silica or calcite cement
Where Found
Montserrat (Spain), Puddingstone localities (England), Death Valley (USA)
Mohs Hardness
2-6 (varies with cement)
Fun Fact
The spectacular mountain of Montserrat near Barcelona is made almost entirely of conglomerate — cemented river pebbles uplifted thousands of meters.
Test Your Knowledge
What does the roundness of pebbles in a conglomerate tell geologists?
Related Specimens
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