Vivianite from the Pleistocene of the Horloff Graben (Hessen, Germany)

The structure of nodules containing vivianite [Fe3(PO4)2.8H2O], and crystal aggregates consisting entirely of this mineral is described on the basis of thin sections. The material studied was collected by the author in a lignite quarry at Wölfersheim near Frankfurt am Main (Germany) from a clay lense, c 5 m below surface. Here vivianite occurs in the form of crystal aggregates which exhibit a radial structure. In the nodules vivianite is found only as patches on the external surface and in cavities. The degree of oxidation varies widely, which explains the various shades of colours seen. It is quite possible that this vivianite formed during two phases.