Bernard,
You may be interested in the following extracts from papers by Stephen Eddy.
The model to which he refers may still be seen at Chatsworth House - it
being a cube of wooden blocks (of different sizes) so arranged as to give
longitudinal and cross sections of the veins and strata near Beevers Shaft.
It is a credit to the marquetry skills of Eddy's model maker (the mine
carpenter?).
Mike Gill
Extracted from: Transactions of the British Association, 1844, pp.52-53
Account of the Grassington Lead Mines, illustrating a Model of the Mine.
By Stephen Eddy
The portion of the mine modelled represents the richest piece of ground as
yet opened in these mines, and includes two extensive fault veins, together
with a piece of ground from which some very rich slickensides have been
obtained. All the ore found near the slickensides is much more refractory in
the furnace, and of less produce than that raised at a distance from it. The
gritstone between the two veins from the points where the slickensides
commenced is also quite altered in its character and appearance.
Extracted from: Report of the British Association, 1858, pp.167-174
On the Lead Mining Districts of Yorkshire
by Stephen Eddy
Here, I would refer to a correspondence, which took place some few months
ago, in the columns of the Mining Journal, on the subject of Slickensides.
It was there asserted that slickensides had never been met with in
Gritstone. I am prepared to meet this assertion, by the production of the
specimen obtained from the Gritstone in the Grassington Mines; and with the
exception of one from the same place, which I gave to the late Duke of
Devonshire, I much question there being a better specimen in the country.
The Slickensides first appeared at the point of junction of two veins and
continued their course in a perfectly straight line in the centre of the
joint vein, for about 70 yards in length, or they might perhaps more
correctly be said to have still divided the two veins, forming the North
side of the one, and the South side of the other. (See Fig, 7.)
We could have procured specimens from either side, with as good a surface as
the one exhibited, but not so large. It was only from the South side that
they could be obtained of any size, the other being so cracked horizontally,
that it was seldom a piece could be broken off, more than an inch or two
wide; in fact, the cracks on this side were almost as numerous as the striæ
on the surface of the North.
The vein throughout the whole length in which the Slickensides were found,
maintained nearly a perpendicular position; and the striæ were as nearly
horizontal. In many parts of the vein, we had the thickness of a foot of
solid ore behind each face of Slickenside.
Many present will no doubt have read or heard of the phenomena reported to
have attended the laying open of Slickensides in Germany; that the miner has
at times been much frightened by the loud reports occasioned by the
explosions.
When driving our level in the Slickenside, we generally worked forward on
the North Side, leaving the South, or strong side, standing for 6 or 8 yards
in length; and on more than one occasion, the workmen spoke of the reports
they heard, sometimes as loud as that of a small pistol. At such times,
numerous places could be seen where pieces had been blistered, and blown
away from the face of the Slickenside; which presented much the same
appearance as a wall recently plastered with very imperfectly-slacked lime,
but on a much larger scale.
The ore from a vein carrying much Slickenside, requires generally a higher
temperature, and is altogether more refractory in the furnace than that from
one free of it.
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