sedimentary

Red Sandstone (Old Red Sandstone)

Ferruginous Sandstone (SiO2 + Fe2O3)

AI-generated identification · may be incorrect

Hardness: 6-7 on Mohs scale; Color: Red, reddish-brown, or pink; Luster: Dull to earthy; Crystal structure: Clastic (composed of mineral grains or rock fragments); Cleavage: None; Specific gravity: 2.2 - 2.8.

Hardness: 6-7 on Mohs scale
Color: Red, reddish-brown, or pink
Luster: Dull to earthy

Identified March 21, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from the lithification of sand-sized grains, primarily quartz and feldspar, in high-energy terrestrial environments like rivers and deltas. The red color is due to iron oxide (hematite) coating the grains. Much of the famous 'Old Red Sandstone' dates back to the Devonian Period (approx. 400 million years ago).

Uses & applications

Used extensively as building stone, flagstone for paving, and as an abrasive. In smaller, tumbled forms found on beaches, it is popular for decorative landscaping and amateur rock collecting.

Geological facts

Red sandstone is famous for preserving early vertebrate fossils and footprints. In the UK and parts of North America, it was the primary building material for many medieval cathedrals and castles due to its relative ease of carving.

Field identification & locations

Identify in the field by its distinct gritty texture (like sandpaper) and 'brick red' color that doesn't wash off. It is commonly found on coastlines in the UK (Scotland/Wales), the Southwestern US, and the Maritimes in Canada. Collectors look for pieces with interesting patterns or embedded fossils.