From Graces Guide
Dolcoath Mine is partly in the parish of Illogan, union of Redruth, hundred of Penwith, Cornwall, within the bounds of the manor or lordship of Tehidy, duchy of Cornwall, and mining district of Camborne; it is situated 12 miles west from the town of Truro, and 3 west of Redruth.
Dubbed 'The Queen of Cornish Mines', Dolcoath was originally a copper mine - output over 350,000 tons - the fifth largest producer in Cornwall and Devon; yet the sixty-seven years between 1853 and 1920 saw it yield the largest output of any Cornish mine of black tin, over 100,000 tons. 
1700s The mine began working in the early 1700's.
1746 The mine was over 300 feet deep.
1788-1799 The mine during the 'Great Copper Slump'. On reopening, it grew to become the largest and deepest mine in Cornwall.
1799-1920 The value of its production was over £10 million (for all minerals). Other minerals of note included ores of arsenic, tungsten, lead, silver, bismuth, cobalt and even uranium.
1805 Trevithick was involved in a fight with Watt at Dolcoath Mine, where Andrew Vivian, as mine manager, was erecting a high-pressure steam-puffer whim-engine to compete with a Watt low-pressure steam vacuum whim-engine.
As the copper ores were mined out, tin was discovered at the lower levels. It mined six different lodes including the Caunter Lode. The principal shafts being at Harriet's, Valley Shaft and Old Sump Shafts. Several other new shafts were sunk at the end of the 19th century such as the New Sump Shaft and New East shaft. Its main Williams Shaft - incidentally named after its chairman Mr. Michael Henry Williams - had an exceptionally rich lode at the 412 fathom (2472 feet) level and the sinking of the shaft began on 26th October 1895. However shortly after World War One, tin prices fell drastically, with new deposits found elsewhere in the world.
1895 The company was registered on 15 July, to take over as a going concern the Dolcoath mine (chiefly yielding tin), situated at Camborne, in Cornwall, which had previously been worked on the cost-book system. The mine is held under lease for sixty years from June, at a royalty. 
1921 The once mighty Dolcoath shut.
The Great Flat Lode is an enormous ore bearing body tilted at an angle of about 45 degrees situated to the south of Carn Brea. Normally lodes are found perpendicular to the ground surface or at best at angles of about 60 degrees. The Great Flat lode got its name as in relative terms it lay a lot flatter in the ground. This, meant that mines could be placed at the optimum locations to extract the tin or copper ore from the ground without digging to excessive depths. The Great Flat Lode Trail encompasses all the major mines of the Camborne-Redruth area running in a 7.5 mile multi-use circular trail around the granite hill of Carn Brea.