Shulamitite Ca₃TiFe³⁺AlO₈ - A new perovskite-related mineral from Hatrurim Basin, Israel

Shulamitite, ideally Ca₃TiFe³⁺AlO₈, is a mineral intermediate between perovskite CaTiO₃ and brownmillerite Ca₂(Fe,Al)₂O₅. It was discovered as a major mineral in a high-temperature larnite-mayenite rock from the Hatrurim Basin, Israel. Shulamitite is associated with larnite, F-rich mayenite, Cr-containing spinel, ye'elimite, fluorapatite, and magnesioferrite, and retrograde phases (portlandite, hematite, hillebrandite, afwillite, foshagite and katoite). The mineral forms reddish brown subhedral grains or prismatic platelets up to 200 mm and intergrowths up to 500 mm. The empirical formula of the holotype shulamitite (mean of 73 analyses) is (Ca_2.992Sr _0.007LREE_0.007)(Ti_0.981Zr _0.014Nb_0.001)(Fe³⁺_0.947Mg _0.022Cr_0.012Fe²⁺_0.012Mn _0.001)(Al_0.658Fe³⁺_0.288Si _0.054)O₈. The X-ray diffraction powder-pattern (MoKa-radiation) shows the strongest lines {d [Å](I_obs)} at: 2.677(100), 2.755(40), 1.940(40), 11.12(19), 1.585(17), 1.842(16), 1.559(16), 3.89 (13), 1.527(13). The unit-cell parameters and space group are: a = 5.4200(6), b = 11.064(1), c = 5.5383(7) Å, V= 332.12(1) ų, Pmma, Z = 2. The calculated density is 3.84g/cm ³. The crystal structure of shulamitite has been refined from X-ray single-crystal data to R1 = 0.029 %. No partitioning among octahedral sites was found for Ti and Fe³⁺ in the structure of shulamitite, these cations are randomly distributed among all octahedra indicating an example of "valency-imposed double site occupancy". The strong bands in the Raman spectrum of shulamitite are at: 238, 250, 388,561, and 742 cm^-1. Shulamitite from the Hatrurim Basin crystallized under combustion metamorphism conditions characterized by very high temperatures (1150-1170 °C) and low pressures (high-T-region of the spurrite-merwinite facies). Chemical data for shulamitite and its Fe-analog from other metacarbonate occurrences (natural and anthropogenic) are given here.