Ecton copper mine

[Re-post from 23/08/2012 gneisslife.blogspot.com]
On Sunday the walk took us past a disused mine as Ecton. A friend asked if it was a lead mine. I looked it up on google and found out that in fact it was a disused copper mine, the only one in the Peak District.
Ecton copper mine - Ecton mine was the source of the 5th Duke of Devonshire’s fortune and was the deepest mine in the world at that time.
The period of time between 1760 and 1790 was the heyday of this famous Peak District mine. The 5th Duke of Devonshire was the lucky owner when a vast deposit of high grade copper ore was discovered. The ore yielded as much as 60% copper, very high grade indeed, many copper ores that are mined today yield only 2 - 3%. This lasted for 30 years and was the source of money used to build Buxton’s Crescent and Stable Block (the latter was later to become the Devonshire Royal Hospital). Below is an image of a sample of chalcopyrite, photographed near the Ecton Copper mine.
In some places this rich ore body was 50m wide. Deeper in the mine, the copper was increasingly replaced by zinc. The shape of the ore body was described by a Dr. Joseph Watson as being a saddle deposit, this being the name that miners gave to locations where ore bodies had been folded by anticline/syncline formations. Samples of the ores from Ecton mine are held both at Chatsworth house in the Peak District and at the British museum in London. The grotto at Chatsworth is lined with chalcopyrites and calcite from the mine.
Ecton is unusual in the Peak District as it is the only source of copper mineralisation. Some lead and zinc ore has been extracted from this mine also. The mine is the deepest in the Peak District and may have been the deepest in the world at the time (at least 1800 feet deep in 1788). A reason for this record is the nature of the deposits - vertical ‘pipes’. Contemporary writers visiting the mine were obviously impressed by the beauty of the ores - yellow, gold, topaz, violet and azure all being mentioned. The ores responsible for this multifarious appearance were (mainly) chalcopyrites with oxides and carbonates. The gangue was mainly yellow calcite with fluorite and iron minerals.
The mine was worked in the 17th century, possibly earlier but never properly exploited. In 1723 a group of speculators re-opened Ecton mine but unfortunately ran out of money before the rich ore body was discovered. In 1763 and 1764 the output was over 1000 tons per year, although this was reduced by the end of the decade.