ashford black marble is a kind of dark limestone, which was mined from ashford-in-the-water, in derbyshire, england. once cut, turned and polished, its shiny black surface becomes very beautiful. strictly speaking, ashford black marble is not a marble formed by heat, but a smooth sedimentary rock, a hard mass of dusty minerals. to make art objects, ashford black marble can be cut as materials of them and put together with other fine stones. derby museum has a diagram of ecton hill made from ashford black marble and other minerals.