Gunnislake: grid reference SX411740

Situated half a mile north east of Latchley, Devon Great United includes West Wheal Maria and also Fortescue Mine. The mine lies on the east bank of the River Tamar and is bounded by Devon Great Consols to the east. Devon Great United worked the two main lodes of Capel Tor Lode and West Maria Lode as well as Fortescue Lode and Devon Great Consols Lode. Shafts sunk on the lodes include Watson's Shaft, Wallesford's Shaft and Fortescue's Shaft.

Production records report that Devon Great United had the following output: From Wheal Fortescue in 1855 - 22 tons of 55% lead ore and 2,640 ounces of silver. From West Maria and Fortescue for the period 1866-78: 10,891 tons of 5.25% copper ore. In 1873 3 tons of 72% lead ore and 1.5 tons of black tin, as well as 8,971 tons of Arsenic ore between 1873 and 1878. As Devon Great United between 1883-84: 4,555 tons of copper ore; 1888-92 902 tons of copper ore and 255 tons of mispickel.