Celestite
Celestite got its name from the celestial blue color in its crystals. Celestite is distinguished by its high specific gravity (density), tabular crystals that resemble barite, relative softness and transparency to translucency. Found in sedimentary deposits, veins and cavities, it is often associated with minerals such as gypsum and dolomite. Most fine specimens today come from Madagascar.
Chemistry: Strontium Sulfate ♦ Class: Sulfates ♦ Group: Barite ♦ Color: Usually blue, can be colorless, yellow and tints of red, green and brown ♦ Luster: Vitreous ♦ Transparency: Transparent to translucent ♦ Fracture: Conchoidal ♦ Crystal system: Orthorhombic ♦ Moh's hardness: 3-3.5 ♦ Localities: Include Lake Erie region of Ohio, Michigan and New York USA; Madagascar; Sicily and Germany