1In this Schedule, " ballast" means any of the following materials, that is to say—
(a)sand, gravel, shingle, ashes and clinker of any description,
(b)broken slag, slag chippings, granite drippings, limestone chippings, slate chippings and other stone chippings (including such materials which have been coated with tar, bitumen or cement),
(c)any other material commonly used in the building and civil engineering industries as a hardcore or an aggregate, and
(d)any other material commonly known in those industries as ballast.