sedimentary
Ironstone Concretion
Ironstone (Siderite/Goethite/Hematite matrix)
Mohs hardness 5.0-6.5; dark brown, reddish-brown, to greyish-black color; dull, earthy to sub-metallic luster; amorphous to fine-grained massive structure; high density and specific gravity (3.0-4.2).
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Physical properties
Mohs hardness 5.0-6.5; dark brown, reddish-brown, to greyish-black color; dull, earthy to sub-metallic luster; amorphous to fine-grained massive structure; high density and specific gravity (3.0-4.2).
Formation & geological history
Formed by the precipitation of iron mineral cements (such as siderite, goethite, or hematite) within sedimentary rock layers, often around an organic nucleus, during early diagenesis in oxygen-poor aquatic environments.
Uses & applications
Historically mined as a low-grade iron ore. Mostly collected as geological curiosities, educational specimens, or decorative landscaping stones.
Geological facts
Ironstone concretions can often be mistaken for meteorites due to their heavy weight, dark weathered exterior crust, and smooth surface contours created by natural erosion.
Field identification & locations
Identify by its heavy weight, dark rusty-brown color, dull exterior, and non-magnetic or weakly magnetic properties compared to true meteorites. Commonly found in sedimentary basins, riverbeds, and coastal cliffs worldwide.
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