sedimentary
Ironstone Pebble
Ferruginous sedimentary rock (Fe2O3 / FeO(OH) mixed with SiO2)
Hardness: 5.0-6.5; Color: Dark brown, reddish-brown, or rusty; Luster: Dull to sub-metallic; Crystal Structure: Amorphous or microcrystalline; Cleavage: None; Specific Gravity: 3.0-4.5 (relatively heavy).
- Hardness
- 5
- Color
- Dark brown, reddish-brown, or rusty
- Luster
- Dull to sub-metallic
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 5.0-6.5; Color: Dark brown, reddish-brown, or rusty; Luster: Dull to sub-metallic; Crystal Structure: Amorphous or microcrystalline; Cleavage: None; Specific Gravity: 3.0-4.5 (relatively heavy).
Formation & geological history
Formed through the deposition of iron-rich sediments or the chemical precipitation of iron oxides in marine or lacustrine environments. This specimen appears water-worn, likely tumbled in a river or creek bed over thousands of years.
Uses & applications
Historically used as a low-grade iron ore. In modern times, used as decorative gravel, in landscaping, or as tumbled stones for hobbyists.
Geological facts
Ironstones often contain hematite or goethite, which gives them their distinctive reddish-brown streak. Some ironstone concretions can contain fossils or unique geometric 'septarian' patterns inside.
Field identification & locations
Identify in the field by its high density compared to other brown rocks and its characteristic rusty weathering. It will often leave a reddish or orange-brown streak if scraped against unglazed porcelain.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
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