Strontium is not as abundant as calcium or barium. It can be found in minerals as the cellestite (that contains SrSO4) and the stroncianite (that contains SrCO3), both relatively abundant in the terrestrial crust, being the first the more common form. Strontium is also found in small amounts associated with other rare-earth minerals. The main deposits of these minerals are found in the USA, the United Kingdom, Germany and Mexico.