Hermannjahnite
A simple copper-zinc sulfate — one of the many rare minerals from Tolbachik's fumaroles.
Intro adapted from Wikipedia (CC BY-SA).
Hermannjahnite is an IMA-recognized mineral species in the sulfate class, with the chemical formula CuZn(SO₄)₂.
It crystallizes in the monoclinic crystal system (space group P2_1/n). It is a member of the Zinkosite structural group.
Key properties: specific gravity 3.74; White streak; Vitreous luster; optically biaxial.
IMA symbol Hjh, IMA status: approved, named in 2015.
Occurs as sublimates around a volcanic fumarole.
It is found associated with Anhydrite, itelmenite, saranchinaite, chalcocyanite, euchlorine, thénardite, aphthitalite, hematite (Saranchinaitovaya fumarole); dolerophanite, tenorite.
The mineral was named to honor Hermann Arthur Jahn, co-author of the Jahn-Teller effect, so pronounced in the structure of hermannjahnite.