Vivianite (Fe2+ Fe2+ 2(PO 4) 2·8H 2O) is a hydrated phosphate mineral found in a number of geological environments. Small amounts of manganese Mg and calcium Pure vivianite is colorless, but the mineral oxidizes very easily, changing the color, and it is usually found as deep blue to deep bluish green prismatic to flattened crystals. Vivianite crystals are often found inside fossil shells, such as those of bivalves , or attached to fossil bone.
It was named by Abraham Gottlob Werner in 1817, the year of his death, after either John Henry Vivian (1785–1855), a Welsh-Cornish politician, mine owner and mineralogist living in Truro , Cornwall, England, or after Jeffrey G. Vivian, an English mineralogist. Vivianite was discovered at Wheal Kind, in St Agnes, Cornwall