It was actually a couple of planks I scavenged from the beach and dried out for a month or two. I thought it might have been decking planks originally; whatever it is its heavy and dense so some sort of tropical hardwood for sure.have they been demolishing any wooden piers/quaysides around you lately? Greenheart was traditionally used for the uprights in piers as, when immersed in water it lasts forever. It was also used to make fishing rods. In fact there was a fishing tackle/gunshop in Cardiff city centre whose founder originally worked building a lot of the piers around Cardiff and he used the greenheart offcuts to make fishing rods and thus opened a shop.