Making products such as bricks, cement and pottery requires that raw clay be mined from natural deposits in the earth. Accessing this naturally occurring substance from places with a known clay deposit often requires that a mine be set up and operated. The term "clay pit" usually refers to the quarry or mine designed and created to provide access to the raw clay.
Clay deposits usually contain varying levels of minerals, such as mica and quartz, so there is a considerable diversity of clay types worldwide. These range from the fine clays used to make ceramics to the rough clay used to make flower pots and the even rougher clay used to line landfills to prevent pollution from leaching into groundwater. Where specific clays are known to exist, an area may contain many clay pits. Clay is needed around the world for many practical purposes, so operating a clay pit near known deposits can be profitable. A substantial industry has developed around mining and selling clay or clay products from various places on the planet.
Quarries and mines are often built in areas with a large amount of a particular type of clay, and a clay pit will likely be located near a large deposit. As with many industrial activities, this type of surface mining can alter a natural landscape dramatically. Clay deposits are usually underground but they are typically mined in huge, open pits, meaning large amounts of surface material must often be removed to another location. When the clay in an area runs out, a clay pit that can no longer profitably produce raw clay might be abandoned.
There are many unused clay pits worldwide that are no longer well maintained. An abandoned clay pit can be dangerous, just like an old coal mine. The landscape near a clay pit might contain steep cliff faces or unstable surface materials. The low areas of the landscape might fill with water. Vegetation might return to the area, though the extent of the damage from the clay mining could mean it would take years.
Despite the risks associated with such areas, it is possible to use an abandoned clay pit for something beneficial once it has stopped producing clay. There are many examples of organizations and townships using a post-mining landscape as public space. In some places, old and unused clay pits have been turned into recreational areas, parks, and other public facilities.