Wikipedia
Millstone Grit is the name given to any of a number of coarse-grained sandstones of Carboniferous age which occur in Northern England. The name derives from its use in earlier times as a source of millstones for use principally in watermills. Geologists refer to the whole suite of rocks that encompass the individual limestone beds and the intervening mudstones as the Millstone Grit Group. The term Millstone Grit Series was formerly used to refer to the rocks now included within the Millstone Grit Group together with the underlying Edale Shale Group.
The term gritstone (usually capitalised by British rock climbers) describes any sandstone composed of coarse angular grains, and specifically refers to such sandstones within the Peak District, Pennines and neighbouring areas of Northern England.
Usage examples of "millstone grit".
Within forty minutes, he was panting on the rounded summit ofMam Tor, high on the ridge where limestone meets millstone grit, the White Peak on his right, the Dark Peak on his left.