Kalistrontite
Kalistrontite is an IMA-recognized mineral species in the sulfate class, with the chemical formula K₂Sr(SO₄)₂.
It crystallizes in the hexagonal crystal system. It is a member of the Palmierite structural group.
Key properties: Mohs hardness 2–2.5; specific gravity 3.3; Vitreous luster; optically uniaxial.
IMA symbol Kst, IMA status: approved, named in 1962.
Found in a drillhole into anhydrite beds, probably formed by the reaction of sylvite with strontium-bearing solutions (Alshtan, Russia); an alteration product of celestine (Pleismar, Germany); in a lake-bed evaporite (Omongwa Pan, Namibia).
It is found associated with Halite, anhydrite, dolomite, sylvite, clay (Alshtan, Russia); halite, sylvite, anhydrite (Pleismar, Germany); gypsum (Omongwa Pan, Namibia).
The name refers to potassium, KALIum, and STRONTium in the composition.