Porcellanite or porcelanite, is a hard, dense rock somewhat similar in appearance to unglazed porcelain.
At Tievebulliagh, Northern Ireland, porcellanite is a tough contact metamorphosed hornfels formed from a lateritic soil horizon within a basaltic intrusive/extrusive sequence.
[2] It is likely that roughouts or roughly-shaped prehistoric tools (celts) were chipped on site before transportation both within Ireland and over the Irish Sea to Britain.
[citation needed] It is also likely that the final polish would have been performed near the site of use in cutting vegetation and trees.
[citation needed] It was commonly polished on grooved blocks of hard sandstone.