Celestine is a mineral composed of strontium sulfate (SrSO₄), renowned for its pale sky-blue color, although it can also be colorless, yellow or reddish, depending on impurities. It crystallizes in the orthorhombic system, often forming tabular or prismatic crystals. Celestine is found mainly in sedimentary rocks such as limestone and dolomite. Appreciated for its beauty, it is prized by mineralogy enthusiasts.