Hermannjahnite is a rare sulfate mineral with the relatively simple formula CuZn(SO<sub>4</sub>)<sub>2</sub>. It is one of many fumarolic minerals discovered on the Tolbachik volcano.
Hermannjahnite is a zinc-analogue of dravertite â another mineral from prolific Tolbachik. Minerals somewhat chemically similar to hermannjahnite include ktenasite and christelite.