Historical reference: Do not rely on this information. It is very old. About this collection
Holmium. a rare metallic element which occurs together with other rare metals in a few minerals - e.g. cerite, gadolinite. There seems to he evidence for believing that, like other so-called elements of the same group (e.g. Didymium), holmium is not a true elementary body, but consists of probably four simple and distinct substances.