Austin Celestine - aka Celestite

Celestine, also known as celestite, is a mineral composed primarily of strontium sulfate (SrSO₄). Its crystal structure is orthorhombic, and it typically forms tabular or prismatic crystals, though it can also be found as granular or fibrous aggregates. The mineral is most recognized for its pale blue color, although it can also appear in shades of white, gray, or red depending on trace impurities. Celestine has a relatively low hardness of 3-3.5 on the Mohs scale, and its specific gravity is around 3.95-4.0. The blue color in the tip of celestine is primarily caused by trace amounts of impurities or structural defects within the crystal lattice. In particular, the blue hue is thought to result from the presence of minor amounts of metal ions, such as iron, that replace strontium in the crystal structure, as well as from the interaction of light with these impurities. 

Austin Celestine refers to rare celestine mineral deposits found in and around Austin, Texas. This mineral occurs in sedimentary rock formations, particularly those associated with evaporite sequences common in the Edwards Plateau region. These formations include limestones or dolomites, reflecting ancient marine environments and evaporation processes that left behind the mineral over geological time.