British Gypsum's Eden Valley mine which mines gypsum principally in the 'A' bed, to supply their Kirby Thore works.
'A' bed is gypsum interbedded with kaolinite and illite and so is ideal for the manufacture of bag plaster as well as plasterboard.
The Mine is worked on a room and pillar system and is the deepest gypsum mine in the world.
Where the gypsum beds dip towards the outer Pennine Fault system the gradient of the workings becomes as steep as 1 in 2.5. In these areas the pillars are trapezoidal in shape in order to bear the added stresses this factor brings.