Itelmenite is a rare sulfate mineral with the formula Na<sub>4</sub>Mg<sub>3</sub>Cu<sub>3</sub>(SO<sub>4</sub>)<sub>8</sub>. It is one of many fumarolic minerals discovered on the Tolbachik volcano.
Saranchinaite and dravertite are examples of other anhydrous complex copper-bearing sulfates, also coming from the Tolbachik volcano.