Strontioperloffite, SrMn22+Fe23+PO43OH3⁠, a new bjarebyite-group mineral from the Spring Creek mine, South Australia, Australia

Strontioperloffite, $SrMn22+Fe23+PO43OH3$⁠, is a new bjarebyite-group mineral from the Spring Creek copper mine, near Wilmington, South Australia, Australia. It occurs as tabular to bladed crystals up to 0.4 mm in size. Associated minerals are copper, cuprite, mitridatite and rhodochrosite. The colour is dark brownish orange and the streak is pale orange. The lustre is vitreous and crystals are translucent. Cleavage is excellent parallel to {100}. Calculated density is 3.89 g/cm³. The mineral is biaxial (–), with α = 1.805(4), β = 1.820(4), γ = 1.829(4). The calculated 2V is 75.0°. Chemical analysis by electron microprobe gave P₂O₅ 31.90, As₂O₅ 0.10, Fe₂O₃ 23.62, Al₂O₃ 0.17, FeO 1.55, MnO 19.41, CaO 0.38, SrO 8.90, BaO 8.65, H₂O_calc 4.08, total 98.81 wt%. The empirical formula based on 15 oxygen atoms is $Sr0.57Ba0.38Na0.01∑0.96Mn1.832+Fe0.142+Ca0.05∑2.02Fe1.983+Al0.02∑2.00P3.00As0.01∑3.01O11.98OH3.02$⁠. The ideal formula is $SrMn22+Fe23+PO43OH3$⁠. The mineral is monoclinic, P2₁/m, with a = 9.1830(18), b = 12.349(3), c = 5.0081(10) Å, β = 100.23(3)°, V = 558.91(19) Å³ and Z = 2. The strongest eight X-ray powder-diffraction lines [d in Å(I)(hkl)] are: 9.055(32)(100), 5.122(23)(120), 3.158(100)(031, 22$1¯$⁠), 3.106(53)(040), 2.985(20)(211), 2.938(22)(140, 310), 2.892(20)(131) and 1.921(53)(222, 350). Strontioperloffite is isostructural with members of the bjarebyite group. The crystal structure was solved from single-crystal X-ray diffraction data using synchrotron radiation and refined to R1 = 4.10% on the basis of 1620 unique reflections with F_o > 4σ(F_o).