Szomolnokite

Szomolnokite is a monoclinic iron sulfate mineral forming a complete solid solution with magnesium end-member kieserite. In 1877 szomolnokite's name was derived by Joseph Krenner from its type locality of oxidized sulfide ore containing iron in Szomolnok, Slovakia.
As of mid-January 2020 the only continent on which szomolnokite has not been found and reported is Antarctica.
At room temperature szomolnokite is stable up to a pressure of 6.2 GPa, and then transforms into Triclinic [crystal system|triclinic] crystal structure.