Ferruginous Sandstone

Physical Properties

Hardness: 6-7 (Mohs). Color: Red-brown, rusty orange, or dark chocolate brown. Luster: Dull/Earthy. Structure: Clastic, fine to medium grainy texture. Specific Gravity: 2.6 - 3.2.

Formation & Geological History

Formed through the lithification of sand grains (usually quartz) where iron oxides like hematite or limonite act as the primary cementing agent. Occurs in fluvial, deltaic, or shallow marine environments.

Uses & Applications

Used primarily as low-grade building stone, filler, or road aggregate. Some high iron-content variations were historically used as low-grade iron ore.

Geological Facts

The 'red rocks' seen in the American Southwest, such as those in Sedona or the Grand Canyon, owe their color to the same ferruginous processes found in this specimen.

Field Identification & Locations

Identify in the field by its grainy, sandpaper-like texture and its tendency to leave a reddish or yellowish streak on a ceramic plate. Look for it in areas with exposed sedimentary strata.

Identified on: 4/20/2026

Mode: Standard