This paper comprises a detailed case study focusing on millstone production in the Mourne Mountains, Co. Down, Northern Ireland, with a specifi c focus on the quarry located on the aptly named Millstone Mountain on the eastern side of the mountain range. Both medieval and post-medieval production techniques and millstone sizes, which differed signifi cantly, are discussed. Research questions concerning quarry placement, geology, transport and chronology of exploitation are addressed. Discussion of post-medieval economic environment in the northeast corner of Ireland is provided with a distribution of known granite millstones surviving within the wider landscape.