Great Britain has a variety of geological natural resources, including coal, natural gas, petroleum, limestone, chalk, salt, iron ore, slate, clay, zinc, tin, silver, gold and lead. Arable land is also an important natural resource. Twenty-five percent of Great Britain's land is used for farming, and 46 percent is pasture land used for grazing livestock.
Historically, coal has been Britain's richest natural resource. During the 19th and 20th centuries, the British produced enough coal to meet most of their own energy needs. In 1970, they were the world's third largest producer of coal. While Britain still has large coal deposits, it has become more economical to produce coal in other countries, and British production has declined steadily. During the 1960s, oil and gas were discovered under the North Sea, and studies showed huge reserves of shale gas below the North Sea floor.
At one time, Great Britain was a significant producer of minerals such as tin and iron oxide. The Cornwall region once had 2,000 tin mines and was one of the world leaders in tin production. Over the course of centuries, Britain's mineral wealth has been depleted, and most of the minerals mined in Britain are those used in construction, such as gravel, sand and limestone.