Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks.[1]
Most sandstone is composed of quartz or feldspar, because they are the most resistant minerals to weathering processes at the Earth's surface. Like uncemented sand, sandstone may be any color due to impurities within the minerals, but the most common colors are tan, brown, yellow, red, grey, pink, white, and black. Because sandstone beds can form highly visible cliffs and other topographic features, certain colors of sandstone have become strongly identified with certain regions, such as the red rock deserts of Arches National Park and other areas of the American Southwest.
Rock formations composed of sandstone usually allow the percolation of water and other fluids and are porous enough to store large quantities, making them valuable aquifers and petroleum reservoirs.[2][3]
Quartz-bearing sandstone can be changed into quartzite through metamorphism, usually related to tectonic compression within orogenic belts.[4][5]
Sandstones are clastic in origin (as opposed to either organic, like chalk and coal, or chemical, like gypsum and jasper).[6] The silicate sand grains from which they form are the product of physical and chemical weathering of bedrock.[7] Weathering and erosion are most rapid in areas of high relief, such as volcanic arcs, areas of continental rifting, and orogenic belts.[8]
Eroded sand is transported by rivers or by the wind from its source areas to depositional environments where tectonics has created accommodation space for sediments to accumulate. Forearc basins tend to accumulate sand rich in lithic grains and plagioclase. Intracontinental basins and grabens along continental margins are also common environments for deposition of sand.[9]