Cornwall has produced two million tonnes of tin, most brought to the surface in the last century.
Tin is found in veins or lodes and unlike coal seams, these tend towards the vertical rather than horizontal.
The tin was laid down 250 million years ago when molten granite intruded into the earth's surface. Superheated waters rich in tin oxide and other chemicals were forced into the surrounding rocks, where they cooled to form veins of tin and copper ore.
The world market for tin remains stable. The metal is used for cans and as a chemical in industrial processes. Production is largely concentrated in Thailand, Malaysia, Indonesia, Brazil and Bolivia. Until 1870, Cornwall and Malaya monopolised tin production. This ended with the discovery of tin in Australia, causing the industry's first recession.
The famous Cornish pasty was originally used by miners as an easy-to- eat sweet and savoury meal, one of the earliest examples of convenience food.