Celestine

Celestine is a mineral composed of strontium sulfate (SrSO₄), famous for its transparent crystals with delicate sky-blue hues, though it can also be colorless, white, yellow, or gray. It primarily forms in sedimentary rocks and geological cavities, where it develops magnificent prismatic crystals. The finest specimens, particularly those from Madagascar, are renowned for their transparency, vitreous luster, and characteristic blue color.