Raman spectroscopy of various phosphate minerals and occurrence of tuite in the Elga IIE iron meteorite

The Raman spectra of phosphate minerals: apatite, merrillite, panethite, brianite, czochralskiite, maricite, new phosphate with composition of Na 2 Fe(Mg,Ca)(PO 4 ) 2 and high‐pressure phase tuite from the Elga IIE iron meteorite are characterized. Panethite, brianite, czochralskiite and new Na‐Fe phosphate were described for the first time. The basic features of all studied phosphates include strong ν 1 symmetric stretching mode of PO 4 3− ions at 950–990 cm −1 , antisymmetric ν 3 vibrations in the 1000–1175 cm −1 region and weak bands in the 400–500 cm −1 region, which correspond to ν 2 bending mode and in the 550–640 cm −1 region, related to ν 4 bending mode. Weak bands at less than 300 cm −1 represent lattice modes. Most of the studied phosphates have three non‐equivalent positions of phosphorus atoms in the crystal structures and can be derived from glaserite, K 3 Na(SO 4 ) 2 , arrangement. Two or three of non‐equivalent [PO 4 ] tetrahedra typically correspond to two or three strong bands in the region of ν 1 vibrations. High‐pressure mineral tuite has similar composition and was formed after merrillite. P‐O vibrations in equivalent [PO 4 ] tetrahedra produce major Raman band of tuite at 972 cm −1 . The Elga parent‐body experienced a shock pressure of at least 12–15 GPa according to minimum pressures of tuite formation in the static high‐pressure experiments. This is the first finding of tuite in iron meteorites and the only second finding of high‐pressure mineral in them.