Citation: Moore, P. B.; Araki, T.; Kampf, A. R.; Steele, I. M. (1976). Olmstaedite, K2Fe2[Fe2(Nb,Ta)2O4(H2O)4(PO4)4], a new species, its crystal structure and relation to vauxite and montgomeryite. American Mineralogist, 61, pp. 5-11.
Formula: Fe2 H4 K Nb0.59 O12 P2 Ta0.41
List type: noninterleaving
List: 3D
Basis: (1;0;0 0;1;0 0;0;1)
Dimensionality: 3
Formula: Fe4 Nb2 O24 P4 Ta2 (Fe2 Nb O12 P2 Ta)
Multiplicity: 1