This report was prepared by the Mineral Economics Section. Part 1 deals with the production of opal and includes sections on the history and present operations in the industry, production and overseas trade statistics, and the types of mining tenures at present available to opal miners. The fields at present being worked are described and the factors which affect production are discussed. Part 2 deals with the marketing of opal and includes sections on the cutting and preparation of stone, markets at home and abroad, and the various factors affecting trade. A number of proposals for improving trade and trading conditions generally are discussed, and the report concludes with a list of references in literature, two graphs showing the value of opal produced in each State and the whole of Australia, from 1890 to 1947, and a map of Australia showing localities mentioned in the text.