The book is an historical monograph on deep-sea mineral-related activities and attitudes towards deep-sea mining in the 20th Century which makes comparisons with the current situation in regard to those activities and attitudes. It reviews developments in the study of, and prospects and plans for mining deep-sea manganese nodules, cobalt-rich crusts, hydrothermal deposits, and phosphorites, and discusses associated environmental, technological, and economic issues. It is based on several sources. First, the author’s experience gleaned from around 50 years of attending conferences on the subject (the most important of which was the annual Underwater Mining Institutes held from 1970 onwards at which much of the material in the book was first exposed), second, discussions with and advice from the author's colleagues on the subject, all attributed, and third, the published literature. The target audiences are marine mining companies and their associates, marine environmentalists, UN and Government administrators responsible for seabed activities, undergraduate students of marine affairs and history, and interested lay persons. Unique features include the widespread sources used including unpublished conference proceedings and reports, personal insights gleaned from more than 50 years of working in the field, the author’s publications dating from 1967-2022, and attributed personal communications from the author’s colleagues.