ˈvivēəˌnīt noun
( -s )
Etymology: German vivianit, from J. G. Vivian, 19th century English mineralogist + German -it -ite
: a mineral Fe 3 (PO 4 ) 2 .8H 2 O 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; sp. gr., 2.58-2.68)