The 40th Forum on the Geology of Industrial Minerals was held in Bloomington, Indiana, from May 2–7, 2004. This Proceedings volume includes 21 papers covering many aspects of industrial minerals, from petrology and geology to economics of production and new technologies: Sonic drilling technology: A look at a unique methodology for determining subsurface lithology, by Timothy J. Augustine; An introduction to diamond tools and their application in the stone industry, by Ken Barnes; Overview of reported water withdrawals by the mineral aggregate industry and the potential utilization of the discharged water for alternative needs, by Mark E. Basch; Microgravity: An Economical Tool for Delineating Voids, by Jeff Bray and J. David Scott; Engineering implications of petroleum contents and carbonate aggregate mineralogy, by L. Lynn Chyi, Harshad L. Pandit, and Robert Y. Liang; The relationship of unconformities to the genesis, alteration, and preservation of bauxite and high-alumina kaolin deposits in the Andersonville District, Georgia, by Mark D. Cocker; Public awareness and the status of industrial minerals in Alberta, by W. A. D. Edwards; Characterization of sand and gravel deposits using S-wave refraction surveys, by Karl J. Ellefsen and William H. Langer; Petrologic controls for fluorspar deposits at Okorusu, Namibia: Hydrothermal replacement of carbonatite, marble, and fenite, by Richard D. Hagni; The Cleves Tunnel, a rare extant example of the use of Buena Vista stone for a canal structure near Cincinnati, Ohio, by Joseph T. Hannibal and Richard Arnold Davis; The Euclid bluestone of northeastern Ohio: Quarrying history, petrology, and sedimentology, by Joseph T. Hannibal, Benjamin A. Scherzer, and David B. Saja; Teaching with tombstones: Geology at the cemetery, by Joseph T. Hannibal; Rare earths in selected U.S. defense applications, by James B. Hedrick; Karst problems in mining of salt deposits in the United States, by Kenneth S. Johnson; Geologic context for industrial minerals of the midwestern United States, by Brian D. Keith; Evaluation of the sodium-sulfate soundness test for qualifying dolomites of northern Arkansas for construction aggregate, by Stephen W. Kline, Wipavan Phiukhao, Melanie L. Griffin, and J. William Miller; Accelerated weathering of limestone for CO2 mitigation: Opportunities for the stone and cement industries, by William H. Langer, Greg H. Rau, and Ken Caldeira; Industrial clays of the midwestern United States, by Haydn H. Murray; The life and times of the Indiana Limestone Institute, by Jim Owens; Recent trends in the industrial mineral and fuel industry of Indiana, by Kathryn R. Shaffer and Nelson R. Shaffer; Ohio's industrial minerals in the twenty-first century, by Mark E. Wolfe;and abstracts of other presentations (posters and talks for which no papers were submitted).