Rozenite is a hydrous iron sulfate mineral, Fe2+SO4·4(H2O).
It occurs as a secondary mineral, formed under low humidity at less than 21 °C (70 °F) as an alteration of copper-free melanterite, which is a post mine alteration product of pyrite or marcasite. It also occurs in lacustrine sediments and coal seams. Associated minerals include melanterite, epsomite, jarosite, gypsum, sulfur, pyrite, marcasite and limonite.[2]
It was first described in 1960 for an occurrence on Ornak Mountain, Western Tatra Mountains, Małopolskie, Poland. It was named for Polish mineralogist Zygmunt Rozen (1874–1936).[2][3]
The thermal expansion of rozenite was studied from −254 °C (−425.2 °F) to 17 °C (63 °F) using neutron diffraction. Rozenite exhibits negative linear thermal expansion, meaning that it expands in one direction upon cooling.[5]