Sandstone is a type of sedimentary rock which forms from a compacted sand aggregate glued together with a mineral cement. It takes an extended period of time for sandstone to form, and the appearance and texture of the rock can vary widely, depending on the composition of the sandstone, and where it formed. There are also a variety of uses for sandstone; among other things, it is a notably popular building material, commonly used for things like tile and flagstones.

The formation of sandstone starts when a layer of sand or finely grained mineral particles forms, often by precipitating out of a river or stream. Over time, the sand becomes compacted by overlying deposits of sediments, resulting in considerable compression. At the same time that the sand is being compressed, water trickling through the higher deposits carries minerals down, and these minerals start to glue the sand together. Left undisturbed long enough, sandstone will form as the mineral cement hardens.

Young sandstone is very friable and crumbly, while mature sandstone can be extremely strong, in addition to being very weather-resistant. Sandstone may acquire a wide range of colors, with rich oranges and yellows being common in desert regions, but it can also be gray, bluish, tan, creamy white, or deeply mottled. Because sandstone is so resistant to weathering, it often forms distinctive geologic monuments.

Argillaceous sandstone is sandstone which contains a great deal of silt, resulting in a comparatively smooth texture. Arkose sandstone has a higher concentration of feldspar, and the composition of this type of sandstone can closely resemble granite. It is also possible to find quartzose sandstone, which contains a very high concentration of quartz. All types are very porous, and sandstone often protects formidable aquifers which can be tapped for water.

In addition to being used as a building material, sandstone can also be carved into statues, used to make kitchenware, and employed in a variety of other tasks. Geologists are fond of sandstone, because it can be used to gather information about the geologic history of a region, and paleontologists often find things of interest in sandstone as well, such as the fossils of animals and plants which happened to be compressed along with the sand.