Sandstone

Sandstone is a clastic sedimentary rock composed primarily of sand-sized grains. The most common constituent is quartz, with feldspar and other rock fragments frequently present. The grains are bound by cementing minerals such as silica, calcite, or iron oxides. By convention, sandstone grains range from about 0.0625 to 2 millimeters in diameter.

Sandstone forms when loose sand is deposited, buried, and lithified through compaction and cementation. It develops in environments such as river channels, beaches, deserts, and deltas, where sand is supplied and preserved. Over time, the grains are cemented to create a coherent rock.

Sandstones are classified by composition and texture. Quartz sandstone is quartz-dominant; arkose contains abundant feldspar; lithic sandstone includes significant rock fragments. Sorting and cement type influence porosity, color, and strength; well-sorted, quartz-rich sandstones often have higher porosity and permeability than poorly sorted varieties.

Properties and uses vary with composition and cement. Porosity typically ranges from about 5 to 25 percent, with permeability depending on sorting and cementation. Sandstones serve as important aquifers and as reservoirs for oil and gas. They are also used as dimension stone in construction and as decorative or architectural material.

Fossils are occasionally preserved in sandstone, and sedimentary structures such as cross-bedding and ripple marks can reveal ancient depositional environments.