Hi John,
The following is from my monograph on The Grassington Mines (British Mining No.46, pp.57-58):-
An interesting phenomenon was found in the Beever Mine, where the Crosscut Vein united with another vein, probably Beever's. This was a slickenside which "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.
"The vein, throughout the whole length in which the slickensides were found, maintained nearly a perpendicular position; and the striae 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.
"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-slaked 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 from it".
The text in itallics comes from:-
Eddy, S. "On the lead mining districts of Yorkshire" Report of the British Association, 1858 pp.167-174.
Stephen Eddy was the Duke of Devonshire's Mineral Agent.
Mike Gill
|