sedimentary

Ferruginous Sandstone

Iron-rich Clastic Sedimentary Rock

AI-generated identification · may be incorrect

Hardness: 6-7 (Mohs); Color: Dark brown, reddish-brown, grey; Luster: Dull to earthy; Structure: Granular, fine-to-medium grained; Cleavage: None; Specific Gravity: 2.3-2.8

Hardness: 6-7 (Mohs)
Color: Dark brown, reddish-brown, grey
Luster: Dull to earthy

Identified July 16, 2026More sedimentary →

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Physical properties

Hardness: 6-7 (Mohs); Color: Dark brown, reddish-brown, grey; Luster: Dull to earthy; Structure: Granular, fine-to-medium grained; Cleavage: None; Specific Gravity: 2.3-2.8

Formation & geological history

Formed through the accumulation and cementation of sand-sized mineral grains or rock fragments, within which iron oxides (hematite or goethite) act as the primary cementing agent. Often found in ancient riverbeds or coastal environments.

Uses & applications

Commonly used as a building stone or road aggregate; historically used in some regions as a low-grade iron ore.

Geological facts

The reddish-brown staining is known as 'desert varnish' when it appears as a thin coating, though here it appears deeply integrated into the matrix. It is extremely common in the Triassic-age basins of the eastern United States.

Field identification & locations

Identify by its gritty sandpaper-like texture and the presence of deep brown or orange-red oxidation. It is frequently found in weathered outcrops or as river cobbles. Collectors look for unique weathering patterns or fossils within the layers.