sedimentary

Ironstone Concretion

Ferruginous Siltstone/Ironstone (Fe2O3)

AI-generated identification · may be incorrect

Hardness: 5-6 (variable); Color: reddish-brown, tan, or deep rust; Luster: dull, earthy; Crystal structure: massive/amorphous; Cleavage: none; Specific Gravity: 3.5-5.0

Hardness: 5-6 (variable)
Color: reddish-brown, tan, or deep rust
Luster: dull, earthy

Identified July 14, 2026More sedimentary →

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Physical properties

Hardness: 5-6 (variable); Color: reddish-brown, tan, or deep rust; Luster: dull, earthy; Crystal structure: massive/amorphous; Cleavage: none; Specific Gravity: 3.5-5.0

Formation & geological history

Formed by the precipitation of mineral cement, typically iron oxides, within the spaces between sediment grains (sand or silt) in sedimentary basins, often over millions of years.

Uses & applications

Primarily used as an iron ore in some regions; also used for landscaping pebbles or decorative specimens.

Geological facts

Concretions are often mistaken for meteorites or dinosaur eggs due to their unusual shapes and heavy weight. They can sometimes contain fossils at their core.

Field identification & locations

Identify by its high density compared to surrounding rocks, distinct rusty orange/brown weathering rind, and its resistance to erosion. Found in sedimentary environments worldwide.