Vivianite was found along fractures in meta-pelitic rocks associated with meta-cherts from Nagasawa,Iwama-machi, Ibaraki Prefecture. The meta-pelitic rocks arerich in graphite, pyrite and pyrrhotite. Vivianite is intimatelyassociated with pyrite and shows very thin tabular crystals, up to10 cm in length. The unit cell parameters are a=10.024(6),b=13.436(3), c=4.693(4) ? and β=102.30(5)°.Decomposition of pyrrhotite and graphite is consideredto have played a key role to produce reduced andFe2+-rich conditions favorable to the vivianite formation.
展开▼
