Definition of vivianite
: a mineral Fe3(PO4)2.8H2O consisting of a hydrous ferrous phosphate that has limited isomorphism with annabergite, erythrite, and koettigite, is colorless when unaltered or blue to green when unaltered but grows darker on exposure, and occurs in monoclinic crystals or fibrous, massive, and earthy (hardness 1.5–2; specific gravity, 2.58–2.68)
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Origin and Etymology of vivianite
German vivianit, from J. G. Vivian, 19th century English mineralogist + German -it -ite
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