Ferruginous Sandstone

Physical Properties

Hardness: 6-7 (Mohs); Color: Reddish-brown, earthy tan, and orange; Luster: Dull/Earthy; Crystal Structure: Clastic (grainy); Specific Gravity: 2.3-2.6

Formation & Geological History

Formed through the accumulation and cementation of sand-sized grains, specifically silica-rich grains bound by iron oxide minerals. Usually found in ancient riverbeds or marine environments where oxygen-rich water interacts with iron.

Uses & Applications

Used primarily in building construction as cladding or pavers, and occasionally as a source of iron ore in low-grade deposits. Valued by collectors for its color variations.

Geological Facts

The reddish color is primarily due to the presence of Hematite. It is often a key component of 'Red Bed' geological formations which signify oxidizing atmospheric conditions during formation.

Field Identification & Locations

Identify by its gritty, sandpaper-like texture and its tendency to leave a reddish streak if rubbed on a harder surface. Common in Southwest USA, Australia, and various basin regions.

Identified on: 5/15/2026

Mode: Standard