Celestine
Celestine crystals are characteristically pale blue and heavy. It is found mainly in limestones and other sedimentary rocks. It can also form during evaporation in arid areas and can be a secondary mineral in some metallic ore deposits. Celestine is found in South Africa. Celestine is also referred to as Celestite.
Chemical Formular : SrSO4
Refractive Index : 1.619 to 1.635
Hardness : 3 – 3½ on the Mohs Scale
Crystal System : Orthorhombic