sedimentary
Rounded sandstone cobble
Quartz-rich sandstone (dominantly SiO₂)
AI-generated identification · may be incorrectTan, fine- to medium-grained, with visible sand-sized grains and reddish-brown iron-oxide streaks; dull, granular surface. Quartz grains have Mohs hardness 7, but sandstone hardness varies with cement; crystal structure is not apparent in the whole rock.
Identified More sedimentary →
Explore Rounded sandstone cobble in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Tan, fine- to medium-grained, with visible sand-sized grains and reddish-brown iron-oxide streaks; dull, granular surface. Quartz grains have Mohs hardness 7, but sandstone hardness varies with cement; crystal structure is not apparent in the whole rock.
Formation & geological history
Sand grains were deposited and compacted, then cemented by silica, calcite, or iron oxides; the cobble was later rounded by water or abrasion. Its precise age and source cannot be determined from the image.
Uses & applications
Sandstone is used as building and paving stone, aggregate, and sometimes decorative material; this rounded cobble is mainly a teaching or collecting specimen.
Geological facts
Sandstone’s properties depend strongly on its grain size and cement, so appearance alone cannot establish its exact composition.
Field identification & locations
Look for gritty sand-sized grains, a granular fracture, and rounded cobble shape; similar material occurs in riverbeds and beaches worldwide. Image-based identification is approximate.
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