Strontium - Occurrence

Occurrence

Strontium commonly occurs in nature, the 15th most abundant element on Earth, averaging 0.034% of all igneous rock and is found chiefly as the form of the sulfate mineral celestite (SrSO₄) and the carbonate strontianite (SrCO₃). Of the two, celestite occurs much more frequently in sedimentary deposits of sufficient size to make development of mining facilities attractive. Because strontium is used most often in the carbonate form, strontianite would be the more useful of the two common minerals, but few deposits have been discovered that are suitable for development.

The mean strontium content of ocean water is 8mg/l.

Strontium metal can be prepared by electrolysis of melted strontium chloride mixed with potassium chloride:

Sr2+ + 2 e− → Sr

2 Cl− → Cl₂ (g) + 2 e−

Alternatively it is made by reducing strontium oxide with aluminium in a vacuum at a temperature at which strontium distills off.

Three allotropes of metallic strontium exist, with transition points at 235 and 540 °C.

According to the British Geological Survey, China was the top producer of strontium in 2007, with over two-thirds world share, followed by Spain, Mexico, Turkey, Argentina, and Iran.