Ferruginous Sandstone

Physical Properties

Hardness: 6-7 (Mohs); Color: Rusty brown, ochre, or yellowish-orange; Luster: Dull or earthy; Crystal structure: Granular (clastic); Cleavage: None; Specific gravity: 2.3-2.6

Formation & Geological History

Formed through the lithification of sand grains where iron-rich groundwater precipitates iron oxides (like goethite or hematite) as a cementing agent between the quartz grains. Typically found in riverbeds, or as part of terrestrial sedimentary sequences.

Uses & Applications

Mainly used as a building stone or road aggregate. Historically used as a low-grade iron ore in some regions. Highly valued as a rough landscape stone.

Geological Facts

The distinct rusty color comes from the oxidation of iron minerals, essentially making this a 'rusted' rock. In some areas, these are called 'ironstones' if the iron content is high enough.

Field Identification & Locations

Identify by its gritty, sandpaper-like texture and its characteristic rusty staining that doesn't wash off. It is commonly found in sedimentary basins and along eroding cliffs or river banks.

Identified on: 5/2/2026

Mode: Standard