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Greenlaws Firestone Level Dig - Deep Vertical Hole (09/11/12)

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I've not been over to the dig since July, and was keen to see the state of the shaft after the kink found in it last time. The chamber has been excavated and progress was well under way downwards in the continuation of the shaft down. It has now changed from being a angled shaft to a vertical one. The chamber now was rather large and the working area was very wide. A lot of timber shuttering and telegraph pole stemples were being installed - the shaft just keeps on eating up timber and scaffold poles as if they were mere snacks! It's a long way down now and the winch has just been installed with over 100m of new cable as the previous one had got too short. I asked Pete to give a more detailed account of what has been going on since my last visit, his report is detailed below:

The last couple of months have centered on making the ground at, and below the Little Limestone safe. This is the point at which two veins diverge - the main Greelaws East Vein is almost vertical at this point, but dies out to a few stringers above the limestone. Our shaft, Gleason's Rise, was driven upwards to the Firestone on a splay vein, which leaves the East Vein at a steep angle. The point at which these two veins meet is geologically complex, and has created a wide (over 3.7m) shatter zone consisting of multiple parallel faults and stringers. Most of this has collapsed into the stopes cut through the Little Limestone, which has meant that we have had a very wide stope to timber and hold apart. This has produced a vast tonnage of rubble, all of which is now on the dump outside. As we sunk through the limestone, we found the remains of ore hoppers, still with lumps of galena in them. As we dropped through the limestone, we expected to find the Limestone Level - this never appeared - rather, a flat floor was discovered, covered with galena and fluorite, and heavily timbered. In the hangingwall, a slot leads down into a continuation of the shaft downwards. Huge round baulks of timber evidently served two purposes - one, they formed the floor of the Limestone level, now collapsed as it was entirely stoped out, and two, they formed the framework for the shaft, and its two hoppers and manway, carrying on downwards. There was no evidence of any rails in the Limestone Level - presumably this was a barrow way, similar to the Flat Drift found by Charles Clark.

Below the limestone is interbedded sandstone and shale (the White Sill) - the vein, now for the first time the main Greenlaws East Vein, has shrunk down to a narrow (around 0.6m wide) stringer composed entirely of crumbly fluorspar with ribs of galena. It has been stoped out on both sides of the shaft, making life hard, as we now have to timber both sides to retain the stope fill. It is interesting that whenever we cut pockets for timber, we are digging in massive galena veins - this must have been a rich mine indeed for the old man to have left such obvious lead ore in place. The footwall has passed through the White Sill, and the shales below it, and is now within the Coal Sills. These lie directly on top of the Great Limestone. Accounts of the geology talk of 18.3m of alternating shales and sandstones between the Little Limestone and Great Limestone. We have passed through over 6m of these so far, so we know that we are less than 12m to our target. The coal sills have just appeared in the hanging wall, which is 2.4m lower than the footwall (the total slip of the fault) By the end of November we hope to have an accurate estimate of the depth we have left to dig - at present, given good conditions, and no equipment failings, we are making a good 1.2 - 1.8m in a weekend.

To assist with progress, the winch has had a brand new 106m cable fitted. New signalling wires have been installed for both the knocker line system, and the telephone. Charles Clark presented me with a copy of his book last weekend - it certainly fuels the enthusiasm to read of the size and extent of the workings that they found connected to the hydraulic shaft - although sobering to learn that they had scarcely found the beginning of the great flats, despite years of digging! In our favour is the strength and experience of the digging team - I think this shows in the technical complexity of the shaft so far, and the fact that it is still progressing downwards - and so far, safely.