John Lawson. Re your post of 20:48 on 30/5/13 on the MINCO thread.
PUMPING
I can’t recall pumping ever being a problem during the years between 1969 and 1981 when as a BSC Research Organisation Geologist I was a regular visitor to the BSC fluorspar mines, despite the workings at Whiteheaps, Groverake and Blackdene all being well below their respective valley floors. When I left BSC in 1981, the Whiteheaps workings had reached the Great Limestone at Sikehead and a drift was being driven back towards the Whiteheaps shafts; Groverake was down to the 80 Fathom Level with drainage via the Tailrace Level off the 30 Fathom Level; and Blackdene was one level down into the Whin. The only slight difficulty was at Whiteheaps which was at the end of a long electricity supply line and subject to a “Main Demand” limit which meant that the power needed for pumping had to be balanced against the needs of the flotation plant resulting in most pumping being done at night. I was not aware of any pumping problems at Allenheads and I can’t see why they could not have been overcome by installing more powerful pumps – unless as with Whiteheaps there was an issue over power supply.
DRAINAGE LEVELS.
The only drainage level from the old Allenheads workings that comes to the surface is the Haugh (or Hough) Level at about 1,170 ft AOD. The possibility of reopening this when work started at Allenheads was considered and the outlet from the adit was located where it ran into the East Allen but in the event it was considered too dangerous a proposition. I have a dye-line print that was taken from a fair copy of an old W B Lead Mine plan and section of the Gin Hill Shaft area at 40 ft = 1 in dated November 1857 that shows the four underground waterwheels and the Horse Track. The section shows the Haugh Level leaving the Gin Hill Shaft area in the Little Limestone just below the bottom of the lowest waterwheel although the accompanying the plan shows it in Burnt Umber ie in beds between the top of Little limestone and the base of the Firestone Sill. Clearly this is far too high to have any impact on workings in the Great Limestone although if it could have been used it would have reduced the pumping head.
WORKINGS TOWARDS THE WEST END.
In dewatering the mine it was necessary to drive west from the Main Incline back to Gin Hill Shaft in order to clear blockages and install pumps etc. but this is where operations should have stopped. All the evidence was that Old Vein was worked out probably by the end of the 18th century and, by the 19th century, workings simply amounted to minor scraping about in the old workings. In addition it was known the vein itself was poor. The description given by Crawhall and quoted in Dunham (1948 p 207 or 1990 p 168) that the vein in the Nattrass Gill Hazle was “strait and ridery, without spar and very little ore” is typical of references to Old Vein found in the old mining records and where it was seen in the Beaumont Mine workings. The only place where the vein carried appreciable amounts of fluorspar seems to have been in the Firestone Sill to the far west in an area where there is a considerable amount of fluorspar scattered about the surface. However, it was known that much of this material had been carted away from surface dumps and the fact that these workings were from shallow shafts into the Firestone Sill and were some of the earliest in the mine (possibly late 17th century) meant that the chance of any workable amounts of fluorspar being left was remote. In my opinion the 2,500 ft of driveage west of Gin Hill Shaft was a completely waste of time and the effort would have been better spent on reaching the south end of Henry’s Vein.
STOPING IN THE GREAT LIMESTONE.
I agree that it would have been necessary to have driven a level below the Great Limestone in order to rework this ground, however, at that stage in the development of Beaumont Mine it was not necessary to work that horizon for the reasons given below.
HENRY’S VEIN
Henry’s vein is something of an anomaly in the NPO. Firstly it strikes N30E rather than the usual N55-65E of the other lead veins and secondly it shows evidence of two major vein oreshoots. These look more like those seen on typical quarter-point veins and there is just a suggestion that they may have been caused by dextral transcurrent movement in the same way that the quarter-point oreshoots were created by sinistral movement. This is well illustrated by the plan and section in Dunham (1948 Plate IV and 1990 Fig 28).
Those diagrams, however, by no means give the full story and we had much more detail when we looked at a copy of the 1897 Abandonment Plans (formerly Mining Record Office No 3608) in the 1970s. These included a detailed geological section along Henry’s vein plotted at 40 ft = 1 in (the section was about 20 ft long) that also showed the stoped areas. The southern oreshoot is particularly impressive and is about 3,000 ft long in beds extending from the Slate Sills down to at least the Three Yard Limestone (the oreshoot does not appear to have been bottomed) with some impressive vein widths reaching over 20 ft in the Slate Sills and very respectable widths elsewhere (see Dunham 1948 p 209 and 1990 p 170). This oreshoot is of similar proportions to Groverake and should always have been kept as the main target for exploration at Beaumont Mine. Indeed if the time wasted on the Old Vein had been applied to Henry’s Vein the outcome of the story could well have been different.
BURTREE PASTURE MINE.
My reference to this was simply to illustrate the use of records of old lead workings being used as an exploration tool. It was not a comment on the success or failure of this project because I have no information on that aspect.
Dave Greenwood.