The Peak District covers an area of about 540 square miles with a great variety of scenery. There are two main areas generally called the White Peak and the Dark Peak. The 'White Peak' is the southern half of the Peak District where greyish-white limestone rocks outcrop at the surface. The 'Dark Peak' is the more northern area where the hard, brown coarse-grained sandstones (millstone grit or gritstone) and large tracts of peat covered moorland can be found. The gritstone fringes the limestone in an inverted U shape to the North, East and West. The majority of the Peak District is in the county of Derbyshire but the outskirts lie in neighbouring counties (Yorkshire, Cheshire and Staffordshire).