The map show the broad distribution of the industrial, including construction, mineral resources of Britain and the main sites where these are worked. Over extensive areas bedrock is covered by superficial deposits, including economically important sand and gravel resources. These superficial deposits are not shown on the map. Resources have been defined by dominant lithology (rock type). The map is a synthesis of the mineral resources and mineral working data held by the BGS in 1996. The published (paper) map has not been superseded however the digital mineral resources and mineral workings data has since been superseded. The map is logically consistent throughout.