This book describes the properties, characteristics, and uses of rare earth elements. It explains where, in what quantities, and how these elements occur in nature, as well as how they are processed from ores into marketable end materials. Retaining its status as a comprehensive monograph for academic, industry, and regulatory professionals, the Second Edition includes a new chapter on the recycling of rare earth elements from devices such as unused batteries and electronics, and is updated throughout with important developments from the past ten years.