Description:A photograph of a piece of rock which is known as a galena. The caption at the back of the photograph reads "This grey mineral with a typical metallic lustre is a lead sulphide known as galena. The milky white mineral intergrown with the galena is a calcium carbonate called calcite. Mined for its lead and sulphur, galena is one of the most common economic minerals found in the Carboniferous rocks of Ireland.".