Sandstone

Sandstone is a clastic sedimentary rock composed mainly of sand-sized minerals or rock grains.

Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow, red, gray, pink, white and black. Since sandstone beds often form highly visible cliffs and other topographic features, certain colours of sandstone have been strongly identified with certain regions.

Rock formations that are primarily composed of sandstone usually allow percolation of water and other fluids and are porous enough to store large quantities, making them valuable aquifers and petroleum reservoirs. Fine-grained aquifers, such as sandstones, are more apt to filter out pollutants from the surface than are rocks with cracks and crevices, such as limestone or other rocks fractured by seismic activity.

Sandstone is mined by quarrying. It is sometimes found where there used to be small sea areas. It is usually formed in deserts or dry places like the Sahara Desert in Africa, the Arabian desert in the Middle East and the Australian desert. In the western United States and in central Australia, most sandstone is red.

Sandstone is converted into quartzite through heating and pressure usually related to tectonic compression within orogenic belts.

Uses

Sandstone has been used for domestic construction and housewares since prehistoric times, and continues to be used.

Sandstone was a popular building material from ancient times. It is relatively soft, making it easy to carve. It has been widely used around the world in constructing temples, cathedrals, homes, and other buildings. It has also been used for artistic purposes to create ornamental fountains an statues.

Some sandstones are resistant to weathering, yet are easy to work. This makes sandstone a common building an paving material. However, some that have been used in the past, such as the Collyhurst sandstone used in North West England, have been found less resistant, necessitating repair and replacement in older buildings. Because of the hardness of individual grains, uniformity of grain size and friability of their structure, some types of sandstone are excellent materials from which to make grindstones, for sharpening blades and other implements. Non-friable sandstone can be used to make grindstones for grinding grain, e.g., gritstone.

Articles is excerpted from http://en.wikipedia.org/wiki/Sandstone