Schwertmannite: A unique mineral, contains a replaceable ligand, transforms to jarosites, hematites, and/or basic iron sulfate

An infrared study is made of the chemical changes of synthetic schwertmannite, which normally is a coal oxidation by-product formed by thiobacillus ferrooxidan bacteria. Schwertmannite, a class of minerals, is a metastable compound that transforms to jarosite, hematite, and/or basic iron sulfate at relatively low temperatures, and is analogous in structure to basic iron sulfate, but with a –Fe–O– cage. A proposed formula for schwertmannite is Fe₄O₄(OH)₂·AN_(2/e)*nH₂O, where AN is the anion andeis its charge, where sulfate can be replaced with other anions, a possible catalyst. The facile conversion of schwertmannite to a black or yellow material might make a useful raw material for the pigment industry.