Includes the mines of Wheal Maria, Wheal Fanny, Wheal Anna Maria, Wheal Josiah, Wheal Emma, which lie from west to east along the main lode and were the principal sources of firstly copper then arsenic in the latter days. Wheal Frementor, Watson's Mine and Bedford United Mine all lie south of the main lode, Frementor (also called Framator) was mined latterly for tin in the most part and did not finally close until 1930.
Ref: Richardson P.H.G. (1991) Mines of Dartmoor & the Taymar Valley after 1913, Devon Books, Tiverton.
Despite earlier attemps the mine did not become a going concern until Josiah Hitchins took up a lease in 1844. The lode was struck just 4 fathoms below the bottom of the previous working in Gard's Shaft at the western end of the sett. Within 6 months and at only 28 fathoms in depth this shaft was 'cutting yellow ore from corner to corner' and in March alone 810 tons of ore was sold.
For the year of 1845 £72,704 profit was divided.
When wheal Fanny was started in 1845 the lode was cut only 3 fathoms below the surface.
In March of 1856 with the lode being worked on its full length from Wh Maria to Wh Emma 3389 tons of ore were sampled, an all time record for Cornwall. The 1856 year total was 28,836 tons. The only limiting factor on output was transport and storage to the quays at Morwellham.
By 1860 the lode at Anna Maria was up to 45 feet wide and yielding up to 80 tons per fathom.
By 1870 refined arsenic was also being produced from arsenopyrite deposits up to 6 feet thick which lined the copper lode and had previously been left in place as having no value. The mine produced over half the British output and only limited output to avoid depressing the world market price.
By 1880 the copper boom was over. Arsenic production sustained the mine for another 20 years until the original compsny folded in 1901.
The overall output from 1844 to 1902 had been 736,229 tons copper ore sold for £3,473,046 and 72,279 tons refinec arsenic for £625,062.
As a means of estimating current worth, miners wages were then 'a few shillings a week'. So even if you multiply the above figures by 100x you still probably have a very low estimate of the value today.
From 'The Mines of East Cornwall and West Devon, D.B. Barton, 1964.