In lithological character, this limestone varies greatly; in one place it is a dark grey, somewhat crystalline limestone, elsewhere it passes into a flaggy, earthy or shaly condition, or even into a mere layer of nodules. When well developed it may reach 50 ft. in thickness in beds of from 1 to 5 ft.; in this condition it naturally forms a conspicuous feature in the landscape because it stands out by its superior hardness from the soft shales above and below.[2]
A P Baggs; G C Baugh; D C Cox; Jessie McFall; P A Stamper (1998), "Introduction", in C R J Currie (ed.), A History of the County of Shropshire: Volume 10: Munslow Hundred (part), The Liberty and Borough of Wenlock, Institute of Historical Research, pp. 1–6, retrieved 22 March 2013