[1][2] The White lias is a rare, fine-grained form of limestone from the late Triassic period, occurring only in certain parts of Somerset and infrequently in Warwickshire.

White lias is part of the Langport Member of the Lilstock Formation,[4] a multi-layered bed of stone formed from shale and limestone.

At its base is a bone-bed yielding ancient marine, reptilian and ammonite fossils.

[3] White lias varies in colour from white-cream to pale grey and is traditionally used for building and flooring.

It is most prevalent in the Somerset towns of Midsomer Norton, Radstock, Langport and Wincanton.