Cleve, Per Teodor (1840-1905)

Swedish chemist and geologist who discovered the elements holmium and hulium 1879. He also demonstrated that the substance didymium, previously supposed to be an element, was in fact two elements, now known as neodymium and praseodymium. Towards the end of his life he developed a method for identifying the age of glacial and postglacial deposits from the diatom fossils found in them.