Sandstone (with Iron Staining)

Physical Properties

Hardness: 6-7 on Mohs scale; Color: Tan, brown, and reddish-orange (due to iron oxidation); Luster: Dull/Earthy; Crystal Structure: Clastic (granular); Cleavage: None/Massive; 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 (rusting) of iron minerals within the rock or cement, often occurring in terrestrial, arid, or river environments.

Uses & Applications

Primary uses include construction (as building stone or crushed aggregate), abrasive material, and as a reservoir rock for petroleum and groundwater.

Geological Facts

Sandstone makes up about 20-25% of all sedimentary rocks on Earth. The varied colors often reflect the different oxidation states of iron minerals acting as a natural cement.

Field Identification & Locations

Field identification: Gritty feel like sandpaper when rubbed, may show visible layers (bedding), and grains do not flake off easily like shale. Commonly found in desert basins, river beds, and coastal areas.

Identified on: 4/20/2026

Mode: Standard