The River Tamar has been the official border between Cornwall and Devon since Saxon times. Mining has been carried out in the Tamar Valley since medieval times. However it was the discovery of rich copper deposits in 1844 that started a mining boom. Other minerals mined in the area included silver, tin, arsenic, lead, and manganese.
By the mid 1800s there were over 100 mines in the valley and Devon Great Consols was the richest copper mine in Europe. Morwellham Quay grew to serve these mines and carry ore down to the sea. The villages of Gunnislake, Bere Alston and Calstock grew as mining boomed.
The East Cornwall Mineral Railway from Kelly Bray to the quays at Calstock opened
in 1872. In 1908, the line was linked by the Calstock Viaduct to the London
and South Western Railway.
The mines of this district worked tin and copper lodes whose outcrops can be
traced from Callington and Kit Hill eastwards to the edge of Dartmoor, crossing
the Tamar Valley between Luckett and Calstock and centred on the settlement
of Gunnislake. Devon Great Consols and Bedford United to the east of the Tamar
and Drakewalls and Gunnislake Clitters to the west were the most important mines
in this area, but other successful groups of mines were worked around Kit Hill
and to the south of Tavistock, with a detached group Dartmoor at Mary Tavy.
The mines of the Bere Alston peninsula, which worked north-south aligned silver
lead lodes are another component of this mining district.
Patterns of land ownership have also effected how the countryside and the
mining ruins have been treated since closure. In Devon, one large estate controlled
some of the most significant sites, and the reversion clause laid on the shareholders
of Devon Great Consols by the Duke of Bedford ensured the clearance of almost
all its buildings within months of its closure, and the subsequent covering
of the site with conifers.
Tavistock is different to any of the towns in the Cornish part of this mining
district. The medieval town of Tavistock was re-modeled by the 7th Duke of Bedford
during the mid-19th century with profits from his mines, and a substantial proportion
of the mining workforce was housed in model cottages built within the town,
at the mines and across his estate.