Agree with Frank and Kev - definitely Caithness. It is the sort of stone that was created by Paul Ysart and then Peter Holmes in the 1970s fo go in the various jewellery - (see Franks site for good examples). The fact that it is battered would indicate that it had come out of a piece of jewellery. There are stones about that have not been used in jewellery. When the Northern Paperweight Society was given a talk by one of the Caithness artists they brought a couple of bags of loose stones.