Strontianite

Strontianite, gray or white mineral, which chemically is strontium carbonate, chemical formula SrCO₃. Strontianite occurs in shallow groundwater or hydrothermal veins. The mineral has a hardness on the Mohs scale of 3.5 to 4 and a specific gravity of 3.7. Strontianite is mined as a source of strontium.