Vivianite

Vivianite is named in honor of John Henry Vivian (1785 - 1855), an English mineralogist and mine owner who first discovered this mineral in Cornwall. Pure, fresh vivianite is colorless but oxidizes very easily and changes color from deep blue to black. It is an iron-phosphate mineral (Fe3[PO4]2.8H2O), formed in an anaerobic system in the presence of dissolved ferrous ions and phosphorous (P) with relatively low sulfide concentrations. It is different from struvite (magnesium ammonia phosphate precipitate) in terms of chemical composition and appearance. Struvite deposits generally appear as white or off-white crystallizations.