sedimentary

Ferruginous Sandstone (Ironstone)

Sedimentary rock with Limonite/Goethite cement

AI-generated identification · may be incorrect

Hardness: 5-6 (variable); Color: Dark brown, reddish-orange, or black; Luster: Dull to earthy; Crystal structure: Clastic (sand grains); Cleavage: None; Specific gravity: 3.0-4.0 (denser than regular sandstone due to iron content).

Hardness: 5-6 (variable)
Color: Dark brown, reddish-orange, or black
Luster: Dull to earthy

Identified April 11, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of sand grains subsequently cemented by iron oxides (like hematite or limonite) precipitated from groundwater. Often found in Phanerozoic sedimentary basins.

Uses & applications

Historically used as a low-grade iron ore; commonly used today as building stone, decorative landscaping, and road base material.

Geological facts

Ironstone nodules like this one often form around organic nuclei like leaves or shells. In many regions, they are known for containing excellently preserved fossils because the iron shell protects the interior.

Field identification & locations

Identify by its distinct rusty-brown streak when scratched against porcelain and its relatively high weight for its size. Look for it in weathered cliffs or as rounded 'nodules' in riverbeds.