sedimentary
Ironstone Nodule
Ferruginous Sandstone / Limonite Concretion
Hardness: 5-5.5 (variable); Color: reddish-brown, tan, ochre; Luster: earthy, dull; Structure: amorphous or fine-grained; Cleavage: none; Heavy for its size due to iron content.
- Hardness
- 5-5
- Color
- reddish-brown, tan, ochre
- Luster
- earthy, dull
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Physical properties
Hardness: 5-5.5 (variable); Color: reddish-brown, tan, ochre; Luster: earthy, dull; Structure: amorphous or fine-grained; Cleavage: none; Heavy for its size due to iron content.
Formation & geological history
Formed through the precipitation of iron oxide minerals (like limonite or hematite) within sedimentary layers, typically in saline or swampy environments during the Phanerozoic eon.
Uses & applications
Historically used as low-grade iron ore; commonly used today in landscaping, construction gravel, or as a decorative specimen for collectors interested in ferruginous formations.
Geological facts
These nodules are often called 'rattle stones' if the interior has weathered away leaving a loose core. They are highly resistant to weathering compared to the surrounding rock.
Field identification & locations
Identify by its distinctive rusty reddish-brown color and high density. Commonly found in eroded creek beds, desert pavements, and sedimentary outcrops worldwide.
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