Demon's Bluff, Anglesea

Vivianite, 2.5mm across

Vivianite nodules up to 20cm across have been found on the beach west of Anglesea on Victoria's south coast. These are usually water-rounded dark blue nodules that sometimes have crystal-lined cavities. It is thought that the nodules formed in an non-oxidising environment in black Anglesea sand, from the reaction of pyrite nodules and organic phosphate material. Very pale siderite has also been described in these nodules, as has an unidentified iron potassium calcium phosphate, with some affinities to leucophosphite (Segnit, 1976).

Large vivianite nodule (polished face), 90mm across

References:

Segnit, E.R., (1976). Vivianite Pebbles from Anglesea, Victoria. Australian Mineralogist No. 5.

Vivianite nodule fragments showing pyrite, each about 30mm across