sedimentary

Ironstone Pebble

Ferruginous sedimentary rock (Fe2O3 / FeO(OH) mixed with SiO2)

AI-generated identification · may be incorrect

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 April 1, 2026More sedimentary →

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Physical properties

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.