A quarry is a large deposit of rock such as granite which is mined for use in construction projects. Quarries can be found all over the world, and most contain a heavy concentration of a particular type of rock such as marble, limestone, slate, or gypsum. In many nations, the word quarry is used interchangeably for two types of quarry: gravel pits, from which gravel and particulate matter are extracted, and dimension stone quarries, from which large chunks of sheets of rock are extracted for use in building. Dimension stone is used to make tiles, flagstones, counters, roofs, and other projects which require large slabs of uniform stone.
Unlike other types of mines, a quarry is usually not dug out underground, and rarely reaches a depth greater than 60 feet (18 meters). A shallow pit is excavated into a deposit of rock which runs close to the surface, and the pit is slowly expanded to remove valuable rock material. If the quarry is being used to extract gravel or fill, explosives may be used to break it up before it is removed and loaded into trucks. If dimension stone is required, the excavation process is more painstaking to ensure that the stone is not damaged.
While a quarry is in active operation, it must be protected from groundwater seepage and rain, or it will turn into a small pond or lake. Many quarries are surrounded with moats of impermeable material to prevent seepage, and are also covered to prevent rain from accumulating in the open pit. In some cases, pumps may be installed to assist with removing water from the quarry. The company which built the quarry also maintains roads to and from the site, and sometimes builds a temporary processing center for the rock so that it can be removed, graded, and processed on site, with excess being disposed at the site rather than miles away.
After a quarry is abandoned, it is usually fenced off or otherwise secured to prevent people from injuring themselves there. In some cases there may be toxins present at the site, due to the way in which the rock was extracted. In others, as the quarry slowly fills with water, it may be a tempting place to swim. However, the quarry may pose hazards to swimming through objects in the water, depth, coldness, or toxins which may have leached into the water. In some cases, an inactive quarry may be converted into a swimming area, with modifications made to create a safe swimming and recreation area.