MM Mine
A preserved 19th-century mine in the heart of the Charterhouse Rakes.
MM Mine, located in the Charterhouse Rakes, is a historically significant site offering a preserved glimpse into 19th-century mining practices. Initially rediscovered by members from the Society for Mines Research in the Bristol Area in the 1970s due to a distinctive “breathing” phenomenon from its entrance, the mine provides invaluable evidence of historical mining techniques, including the use of fire-breaking and early shot-hole methods. Its primary importance lies in its well-preserved historical artefacts and features, which paint a detailed picture of the challenges and methods of miners from a bygone era.
History and Exploration
The “Breathing” Shaft (1970s)
The mine was first noted during a winter survey when cavers observed it “breathing” – a sign the shaft’s fill was not solid. A 1972 report in the Axbridge Caving Group News noted, “we found one of the small depressions ‘breathing’. This suggested loose filling in the mineshaft.”
Later that year, the entrance was “uncorked” by removing loose boulders. Early explorers hoped to find tools or boot prints but instead found rotten tree branches that had originally supported the fill.
Video: The ‘breathing’ mine entrance
Reopening and Modern Exploration (2007)
Interest in the “breathing” shaft led to further investigation in April 2007. Beyond the 14m entrance pitch, a dig through a slim vein led to the discovery of a larger rift filled with stacked deads and poised boulders, aptly named the “Chapel of Doom.”
Subsequent efforts pushed through a 6m crawl to a T-junction. As of 2007, the mine is approximately 40m long and 20m deep. While a strong draught suggests further potential, explorers noted that “future digging will be tricky!”
Mine Description
The Entrance and Shafts
The entrance to MM Mine is a rift that descends vertically for about 30 feet (9m) before offsetting to the south for another 15 feet (4.5m), where it enters a small bedding chamber. A key feature is a narrow, secondary “false shaft” that joins the main shaft part-way up. This is believed to have been used for ventilation, as evidenced by burned rock at its base, and is too small for hauling or climbing.
The Bedding Chamber and Beyond
The first significant space is a bedding chamber approximately 10 feet long by 5 feet wide. From here, the 2007 exploration pushed through to the “Chapel of Doom” and the subsequent crawl and T-junction. Despite the draught, the mine is still considered to be well above the level of Upper Flood Swallet.
Evidence of Mining
Mining Techniques
The walls show clear evidence of fire-breaking, followed by drilling and blasting, with numerous shot marks (0.75 to 1 inch, star-drilled) characteristic of the 1850s.
Haulage Marks
A distinct rope groove is visible where the main shaft changes direction, fitting a 1-inch rope snugly, indicating a significant quantity of ore was hauled out.
Footwear
While no boot prints were found, some earth was padded down in a manner that suggested the use of soft-soled shoes.
The Vein
Only one vein is visible, appearing as a double band of calcite (“Beef”), with no visible Galena and only a trace of sandy oxide.
Dating the Workings
Analysis of wood used for supports dated activity to the mid-19th century, suggesting a re-exploration by Cornish Miners of older workings.
Timbering
The original shaft fill was supported by 2.5-inch thick tree branches, which had decomposed into a carbonised paste by the 1970s.