Mud and metal; the impact of historical mining on the estuaries of SW England, UK

Visitors and residents alike enjoy the countryside and coast of SW England because of the stunning landscapes and natural environment. Many will also be aware, largely through the industrial archaeological record and world heritage site designation, of the historical importance of mining in this region. Separate mineralization episodes, primarily during the Permian and Triassic, led to the formation of a world-class polymetallic ore field, with major deposits of not only tin (Sn) and copper (Cu), but also iron (Fe), lead (Pb), arsenic (As), zinc (Zn), tungsten (W) and silver (Ag), along with minor occurrences of less common metals such as uranium (U), antimony (Sb), nickel (Ni), cobalt (Co), bismuth (Bi) and gold (Au). Mining of alluvial deposits commenced in the Bronze Age, with hard rock mining commencing by the late thirteenth century and continuing intermittently, as metal prices rose and fell, to the present day. With hard rock mining, came the processing or ‘dressing’ of ores during which they were crushed so that minerals of interest could be recovered. The wastes from this process—mine tailings—were historically released into rivers and transported towards the coast as man-made sediments. Deposition occurred in many of the estuaries around SW England, which consequently preserve a record of the development and historical impact of mining.