VIVIANITE (from the name of the discoverer, the English mineralogist J. G. Vivian * EN: vivianite, blue iron earth, blue oches; DE: Vivianit; FR: vivianite; ES: vivianita; RU: вивианит) is the mineral of the class of phosphates, Fe3[PO4]2•8H2O. Vivianite contains 43% of the FeO, and approximately 28% of the P2O5. The usual impurities are the Mn2+, Mg, and Ca. Vivianite crystallizes into the monoclinic crystal system. The crystals are prismatic, columnar, acicular, less often tabular. There are characteristic the stellate and radial-radiant intergrowths, spherolites, nodules, earthy and powdery masses. The fresh specimens are colourless, the mineral is easily oxidized when exposed to the air, while acquiring the pale-blue, indigo-blue, to black-blue colouration. The earthy masses are pale-blue to dark-blue. The hardness is 1.5-2. The density is up to 2700 kilograms per cubic metre.

Vivianite is the supergene mineral. Vivianite is formed under the reductive conditions with the availability of the (PO4)3- ions within the solutions. Vivianite may be found within the sedimentary rocks and ores, within the peats, lignites, forest soils, and so on. The beautiful radiant aggregates of vivianite are distributed within the Kerch deposits of the phosphorus-containing limonites within the Crimea peninsula. Vivianite in the form of the earthy interlayers exists within many peat bogs. Vivianite also emerges during the change of the iron-manganese phosphates within the rare-metallic pegmatites. Vivianite may be used as the blue paint.