This book offers a comprehensive overview of the structure and solubility of the mineral schwertmannite, while also delving into characterization methods and techniques, environmental stability, and the potential to retain pollutants. Using examples from the 1990s, when the mineral was first discovered, Schwertmannite compiles years of research in this supplementary guide. Chapter 1 explains its occurrence in various environmental settings, the conditions of its formation, and its association with other secondary precipitates. Chapter 2 discusses its solubility, structure, and iron–sulphur coordination, while Chapter 3 delves into synthesizing approaches such as dialysis techniques, oxidation pathways, and urea hydrolysis. Chapter 4 explores how schwertmannite came to be characterized based on colour, composition, morphology, and crystallinity. The last two chapters deal with the mineral’s interaction with contaminants, its binding mechanisms, its metastability with respect to other iron oxyhydroxides, and the factors controlling transformation processes. This book will benefit a large community of scientists and researchers working in acid mine drainage, since schwertmannite is the most abundant mineral in these sulphate-rich environments. It will be a valuable body of knowledge for research organizations and mining companies, as well as those teaching courses on mining, mineral chemistry, wastewater treatment, acid sulphate soils, soil geochemistry, and mine reclamation.