"The Northern Iron River area, commonly known as Mineral Hills, comprises about 7 square miles near the northwest margin of the Iron River-Crystal Falls synclinorium. Because of thick glacial deposits, bedrock geology is known mainly from mine workings and drill exploration. Rock units, from oldest to youngest, are: (1) tightly folded strata of the Animikie Series, which includes Badwater Greenstone, Dunn Creek Slate. Riverton Iron-Formation, and Hiawatha Graywacke; (2) metadiabase dikes and sills, and; (3) at least one diabase dike of Keweenawan age. Faults dominate the structure, particularly the North Mineral Hills fault and the South Mineral Hills fault, both east-northeast reverse faults of large displacement. The general distribution of iron ore bodies in relation to synclinal structures is shown in cross sections, maps, and sketches. A brief history, description, and production for each mine. and descriptions of all known explorations are given. Partial extent of mine workings, drill-hole information, and magnetic survey data are shown on a geologic map."--Abstract.