Baryte, BaSO4, Barium sulphide, is a common gangue mineral associated with lead ore deposits, and this applies to this specimen collected from the White grit mine, Shelve, in Shropshire. The specimen appears to be structured in layers, and is quite heavy at 9 Kg. I remember that I made an improvised rucksack to carry it about half a mile, by tying the sleeves of my jumper together. Baryte is also a useful mineral, with about two thirds of world production used as a weighting agent in oil drilling