sedimentary
Ironstone / Hematite Concretion
Iron oxide / Fe2O3
Hardness of 5.5 to 6.5 on the Mohs scale, reddish-brown to dark gray color, metallic to dull earthy luster, amorphous or cryptocrystalline structure, no true cleavage, and a noticeably high specific gravity making it feel heavy for its size.
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Physical properties
Hardness of 5.5 to 6.5 on the Mohs scale, reddish-brown to dark gray color, metallic to dull earthy luster, amorphous or cryptocrystalline structure, no true cleavage, and a noticeably high specific gravity making it feel heavy for its size.
Formation & geological history
Formed through the precipitation of iron-rich mineral cements in sedimentary environments, often found as nodules or concretions in sandstone or weathered soils over millions of years.
Uses & applications
Primarily collected as a geological specimen, sometimes tumbled or polished for decorative stones or lapidary art.
Geological facts
Ironstone concretions are often weathered out of softer surrounding rock due to their higher resistance to erosion, leading to smooth, rounded, often unusually shaped natural pebbles.
Field identification & locations
Easily identified in the field by its reddish-brown rust color, smooth weathered surface, and notably heavy weight compared to normal quartz pebbles of the same size.
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