sedimentary

Sandstone (Ferruginous)

Arenite (Fe-rich)

Hardness: 6-7 (Mohs scale); Color: Brown, reddish-brown, tan; Luster: Dull/Earthy; Crystal structure: Clastic (grain-based); Cleavage: None; Specific gravity: 2.2–2.8

Hardness: 6-7 (Mohs scale)
Color: Brown, reddish-brown, tan
Luster: Dull/Earthy

Identified March 25, 2026More sedimentary →

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Physical properties

Hardness: 6-7 (Mohs scale); Color: Brown, reddish-brown, tan; Luster: Dull/Earthy; Crystal structure: Clastic (grain-based); Cleavage: None; Specific gravity: 2.2–2.8

Formation & geological history

Formed through the accumulation and cementation of sand-sized mineral particles or rock fragments. The reddish-brown color indicates iron oxide (hematite or limonite) acting as the cementing agent. These can date from the Precambrian to recent periods depending on the deposit site.

Uses & applications

Commonly used as a building material, paving stone, and in the manufacturing of glass when high in silica. For collectors, it serves as a representative sedimentary specimen or a substrate for fossils.

Geological facts

Sandstone makes up about 20% of all sedimentary rocks on Earth. The iconic 'Red Rocks' of the American Southwest are primarily ferruginous sandstones. It often preserves ripple marks and cross-bedding from ancient water currents.

Field identification & locations

Identify in the field by its gritty, sand-like texture (feels like sandpaper) and visible layering. It is commonly found in basins, riverbeds, and desert regions. Collectors should look for unique cross-bedding patterns or fossil inclusions.