<P> Side products from this process include ferrophosphorus, a crude form of Fe P, resulting from iron impurities in the mineral precursors . The silicate slag is a useful construction material . The fluoride is sometimes recovered for use in water fluoridation . More problematic is a "mud" containing significant amounts of white phosphorus . Production of white phosphorus is conducted in large facilities in part because it is energy intensive . The white phosphorus is transported in molten form . Some major accidents have occurred during transportation; train derailments at Brownston, Nebraska and Miamisburg, Ohio led to large fires . The worst incident in recent times was an environmental contamination in 1968 when the sea was polluted from spillage and / or inadequately treated sewage from a white phosphorus plant at Placentia Bay, Newfoundland . </P> <P> Another process by which elemental phosphorus is extracted includes applying at high temperatures (1500 ° C): </P> <Dl> <Dd> 2 Ca (PO) + 6 SiO + 10 C → 6 CaSiO + 10 CO + P </Dd> </Dl> <Dd> 2 Ca (PO) + 6 SiO + 10 C → 6 CaSiO + 10 CO + P </Dd>

Where is most of the phosphorus on earth found