Sandstone

Physical Properties

Hardness: 6-7 (on Mohs scale if quartz-rich); Color: Brown, tan, yellow, or reddish-brown due to iron oxide; Luster: Dull or earthy; Crystal structure: Granular/Clastic; Cleavage: None (fractures across grains); Specific Gravity: 2.2-2.8

Formation & Geological History

Formed through the accumulation and cementation of sand-sized mineral grains or rock fragments (0.0625 to 2 mm). Usually deposited in deserts, riverbeds, or beaches over millions of years and lithified by pressure and mineral cements like silica or calcite.

Uses & Applications

Commonly used as a building stone (brownstone), paving material, in glass manufacturing (if high silica content), and as an aquifer for groundwater and reservoir for oil and gas.

Geological Facts

Sandstone makes up about 20% of all sedimentary rocks on Earth. Famous geological formations like the Grand Canyon and the 'Red Rocks' of the American Southwest are primarily composed of various sandstone layers.

Field Identification & Locations

Identify in the field by its 'sandpaper' feel when rubbed. It often shows visible bedding planes or cross-bedding. Common in river valleys and coastal regions. It is a fundamental rock for beginner collectors to understand depositional environments.

Identified on: 4/26/2026

Mode: Standard