Ferruginous Sandstone

Physical Properties

Hardness: 6-7 (Mohs scale); Color: Brown, reddish-brown, tan, with earthy gray undertones; Luster: Dull/Earthy; Crystal structure: Clastic (sand-sized grains); Cleavage: None/Conchoidal fractures; Specific gravity: 2.2 - 2.8.

Formation & Geological History

Formed through the accumulation and cementation of mineral particles or rock fragments (detritus). The brown-reddish staining indicates the presence of iron oxide (hematite or limonite) that acted as the cementing agent or has weathered over geological time.

Uses & Applications

Commonly used in construction as crushed stone or building material. Historically used for architectural facades and walling. Low-quality specimens are mostly significant for landscaping.

Geological Facts

Sandstone makes up about 20% to 25% of all sedimentary rocks on Earth. The rusty color often tells a story of ancient oxygen levels in the environment during deposition.

Field Identification & Locations

Identify in the field by its gritty texture (feels like sandpaper) and distinct layering or bedding planes. It is often found in river beds, deserts, and coastal areas where sediment accumulates.

Identified on: 4/20/2026

Mode: Standard