Sandstone (Ferruginous)

Physical Properties

Hardness: 6-7 on Mohs scale (due to quartz grains); Color: Tan, reddish-brown, or orange due to iron oxide staining; Luster: Dull/Earthy; Crystal structure: Granular/Clastic; Cleavage: None; Specific Gravity: 2.2-2.8

Formation & Geological History

Formed through the accumulation and cementation of sand-sized mineral grains or rock fragments. The reddish hue indicates oxidation during burial or exposure. These rocks can form in deserts, riverbeds, or coastal environments over millions of years.

Uses & Applications

Commonly used as a building material, gravel, and in glass manufacturing if the quartz content is high. In smaller specimens, it is primarily of educational or decorative value for amateur collectors.

Geological Facts

Sandstone makes up about 20-25% of all sedimentary rocks on Earth. The 'red rocks' of the American Southwest, such as those in the Grand Canyon and Zion National Park, are massive formations of ferruginous sandstone.

Field Identification & Locations

Identify in the field by its sandpaper-like texture. It can often be scratched by a steel nail but will scratch a copper penny. Found globally in basins and near current or ancient shorelines.

Identified on: 4/16/2026

Mode: Standard