What is "sussex marble"

Petworth marble \Pet"worth mar"ble\ A kind of shell marble occurring in the Wealden clay at Petworth, in Sussex, England; -- called also Sussex marble.

Sussex Marble is a fossiliferous freshwater limestone material which is prevalent in the Weald Clay of parts of Kent, East Sussex and West Sussex in southeast England. It is also called Petworth Marble, Bethersden Marble or Laughton Stone in relation to villages where it was quarried, and another alternative name is winklestone. It is referred to as "marble" as it polishes very well, although it is not a geologically described one as it has not been subject to metamorphosis. The matrix is made up of the shells of freshwater gastropods and viviparus winkles, similar to but larger than those making Purbeck Marble. The pale calcified remains of the shells are in a matrix of darker material. West Sussex has a good concentration of thin layers of Sussex Marble; beds typically measure no more than thick. There are often two beds—the lower formed of smaller-shelled gastropods than the upper—with a layer of calcareous clay between them.