sedimentary
Conglomerate (pebble conglomerate)
Clastic sedimentary rock composed of rounded gravel-sized clasts in a finer matrix
AI-generated identification · may be incorrectVisible rounded pebbles and granules of mixed colors and compositions cemented in a tan-brown matrix; hardness and luster vary with the clasts and cement. Clasts are poorly sorted and larger than 2 mm; no single crystal structure or Mohs hardness applies.
Identified More sedimentary →
Explore Conglomerate (pebble conglomerate) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Visible rounded pebbles and granules of mixed colors and compositions cemented in a tan-brown matrix; hardness and luster vary with the clasts and cement. Clasts are poorly sorted and larger than 2 mm; no single crystal structure or Mohs hardness applies.
Formation & geological history
Forms when rounded gravel is deposited in energetic rivers, beaches, or alluvial fans, then buried and cemented by silica, calcite, or iron-rich minerals. Its age cannot be determined from the photograph.
Uses & applications
Commonly used as decorative building or landscaping stone and collected as a hand specimen; this small piece has little commercial value.
Geological facts
The rounded clasts indicate transport and abrasion before burial, unlike the angular fragments of breccia.
Field identification & locations
Identify it by pebbles larger than 2 mm that are rounded and visibly cemented together. Conglomerates occur in ancient river, shoreline, and alluvial-fan deposits worldwide.
More like this
Other sedimentary specimens
Fossiliferous Sedimentary Rock
Sedimentary limestone with invertebrate fossil imprint
fossil
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sandstone
Arenite
sedimentary
Quartz pebble
Silicon dioxide (SiO2)
sedimentary
Shale
Shale (clastic sedimentary rock)
sedimentary
Shale (or Mudstone/Siltstone)
Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)
sedimentary