A complex zirconium titanium oxide with three polytypoids known (2M, 3O, 3T).
Gieré et al. (1998) identified five hypothetical end-members, CaZrTi2O7, CaZrMe5+Me3+O7, ACTZrTiMe2+O7, REEZrTiMe3+O7 and REEZrMe5+Me2+O7. The last one has been observed as a 53% percentage of REEZrNb(Mn,Fe)O7 in a sample from the Eifel volcanic region (Della Ventura et al., 2000).
Originally described as a new mineral given the name polymignite by Berzelius (1824) from a syenite pegmatite atFredriksvärn (now: Stavern), Vestfold, Norway. The specimens were collected by Nils Otto Tank (1800-1864) around 1823-1824, when he was a student of mineralogy. Polymignite at Stavern is metamict. Brögger (1890) described in detail the morphology and the chemical and physical properties. Lima-de-Faria (1958) found that recrystallization at 700℃ of the type material gave a cubic phase (with fluorite structure). Pudovkinaet al. (1969) calculated, based on the axial ratios (0.712:1:0.512) given by Brögger (1890) and the cell unit volume, that polymignite is orthorhombic. Later shown to be identical with zirconolite described in 1956, and subsequently discredited in 1988. In spite of its priority and wide use in the literature, polymignite is now considered a metamict, originally orthorhombic variety of zirconolite.
Haifleret al. (2021) investigated three samples of metamict "Polymignite" from different syenite pegmatites near Stavern and found that the chemical composition corresponded to the zirconolite-related mineralsstefanweissite andnöggerathite-(Ce).