not surprised with perssommons they dont know their arse from their elbow, a special kind of useless they are. anhydrite will be alot lighter in colour, will dust up like a flooring compound if you put a stone/buffer on it and will also 99/100 have latiance on it, once you have seen it once it is easy to spot compared to anything cement (or at least in my mind it is) generally speaking it should be of a high quality level wise too.
