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. |
