Gritstone

Gritstone or grit is a hard, coarse-grained, siliceous sandstone. This term is especially applied to sandstones quarried for building material.

British gritstone was used for millstones to mill flour, to grind wood into pulp for paper and for grindstones to sharpen blades. "Grit" is often applied to sandstones with angular sand grains. It may commonly contain small pebbles or breccia.Neuendorf K.K.E; Mehl J.P. Jr. & Jackson J.A. (eds) 2005. Glossary of Geology. 5th ed, Alexandria, Virginia, American Geological Institute. 

Millstone Grit is an informal term for gritstones  found in the Peak District and Pennines of northern England. These sediments were laid down in the late (upper) Paleozoic era, in the Carboniferous period, in deltaic conditions. The Millstone Grit Group is a formal stratigraphic term for this sequence of rocks.Wilson, Alfred 1992. Geology of the Yorkshire Dales National Park. Grassington: Yorkshire Dales National Park Committee. 

 References 

Category:Sedimentary rocks
Category:Geography of England