Goryainovite, Ca2PO4Cl, is a new halophosphate, the chlorine analogue of 'spodiosite', Ca2PO4F. It is orthorhombic, Pbcm, a = 6.215(2), b = 7.011(2), c = 10.788(3) angstrom, V = 470.0(8) angstrom(3), Z = 4 (from powder X-ray diffraction data). The mineral is found in a magnetite-serpentine rock of the Stora Sahavaara iron ore deposit (67.408 degrees N 23.297 degrees E) where it forms small (up to 20 mu m in diameter) rounded inclusions in magnetite, in close association with hydroxylapatite-chlorapatite, pyrrhotite, pyrite, chalcopyrite, valleriite and thorianite. Goryainovite is a transparent, colourless mineral with a vitreous lustre and a white streak. Cleavage is not observed, and the fracture is conchoidal. The Mohs hardness is c. 4. In transmitted light, the mineral is colourless, biaxial (-), beta approximate to 1.66 (for lambda = 589 nm). D-calc = 2.98 g.cm(-3). The mean chemical composition specified with electron microprobe is (wt.%): P2O5 33.19, Cl 16.96, CaO 53.25, O = Cl -3.83, total 99.57. The empirical formula calculated on the basis of 3 cations per molecule is Ca-2.01 [P0.99O3.98]Cl-1.01. The simplified formula is Ca2PO4Cl. The strongest X-ray powder diffraction lines [d in angstrom, (I), (hkl)] are 2.845(90)(113), 2.746(100)(211), 2.333(25)(114), 2.028(15)(132), 1.9569 (30)(115), 1.8370 (20)(025). The Raman spectrum of goryainovite includes 10 bands of PO43--group vibrations. Goryainovite represents probably an early-formed phosphate of the magnetite-serpentine rock and crystallized together with magnetite. When chlorine fugacity decreased, almost all goryainovite was transformed into chlorapatite-hydroxylapatite, and only grains isolated in magnetite remained unaltered. The mineral is named in honour of Prof. Pavel M. Goryainov (b. 1937) for his contribution to the knowledge of the geology and petrology of banded iron formation of the north-eastern part of the Fennoscandian Shield.
