Celestite

Celestine (SrSO) is by far the most common Strontium mineral, originally named in German referencing the faint blue color of the original specimen Andreas Gotthelf Schütz had in 1791. It’s found on every continent, typically in sedimentary rocks, along with other evaporite deposits like Gypsum, Barite, and Halite, and in limestone and Dolomite.