sedimentary
Dark ironstone concretion (probable)
Iron-oxide-rich sedimentary concretion, likely hematite/goethite cementing sand or clay
AI-generated identification · may be incorrectDark brown to nearly black, dull and earthy, irregular rounded form with fractures; hardness and composition cannot be confirmed from the image. Ironstone commonly has variable hardness and no distinct crystal structure or cleavage.
Identified More sedimentary →
Explore Dark ironstone concretion (probable) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Dark brown to nearly black, dull and earthy, irregular rounded form with fractures; hardness and composition cannot be confirmed from the image. Ironstone commonly has variable hardness and no distinct crystal structure or cleavage.
Formation & geological history
Likely formed as iron oxides cemented sediment around a nucleus during groundwater circulation; such concretions occur in sedimentary deposits of many ages.
Uses & applications
Primarily a collector’s specimen; ironstone has also been used as iron ore and, when suitable, as building stone.
Geological facts
Its rounded, knobby shape and rusty-brown broken areas are consistent with an iron-rich concretion, but visual identification alone is uncertain.
Field identification & locations
Look for a heavy feel, rusty streak, and magnetic response (some ironstones are magnetic); common in sedimentary terrains worldwide. Confirm with a streak or composition test.
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