sedimentary
River Pebble (Siltstone/Mudstone)
Clastic sedimentary rock
Hardness: 3-5 (Mohs scale), Color: Dark brown to reddish-brown, Luster: Dull/Earthy, Crystal structure: Fine-grained/Aphanitic, Cleavage: None (conchoidal or irregular fracture), Specific gravity: 2.3-2.6
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 3-5 (Mohs scale), Color: Dark brown to reddish-brown, Luster: Dull/Earthy, Crystal structure: Fine-grained/Aphanitic, Cleavage: None (conchoidal or irregular fracture), Specific gravity: 2.3-2.6
Formation & geological history
Formed through the accumulation and compaction of fine-grained clay and silt particles in low-energy aquatic environments such as riverbeds, lakes, or floodplains. This specimen shows significant rounding due to aqueous erosion over long periods.
Uses & applications
Primarily used in landscaping, road construction gravel, or as a substrate in aquariums. These smooth stones are also popular for painting or decor.
Geological facts
The rounded shape is a result of 'saltation' where the rock bounces along a river bottom, chipping away sharp edges. These stones can often contain tiny micro-fossils or organic matter.
Field identification & locations
Identify by its smooth, water-worn texture and fine grain size where individual crystals are not visible to the naked eye. Found worldwide in active or ancient riverbeds and shorelines.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone (Quartz-rich)
Arenite (SiO2)
sedimentary
Sandstone (with man-made markings)
Arenite (composed primarily of Quartz, SiO2)
sedimentary