vivianite

noun

viv·​i·​an·​ite

ˈvivēəˌnīt

plural -s

: 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)

Word History

Etymology

German vivianit, from J. G. Vivian, 19th century English mineralogist + German -it -ite

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