Xieite, a new mineral of high-pressure FeCr2O4 polymorph

Xieite, a new mineral, occurs in the shock vein of the Suizhou meteorite. The mineral has an orthorhombic structure and its space group is Bbmm. The cell parameters are a = 9.462(6) Å, b = 9.562(9) Å, c = 2.916(1)Å. The crystal-chemical formula is (Fe_0.87Mg_0.13Mn_0.01)_1.01(Cr_1.62Al_0.25Ti_0.08V_0.02)_1.97O₄, or simply formula FeCr₂O₄. Stronger X-ray diffraction lines are [d (Å), lll _o]: (2.675, 100), (2.389, 20), (2.089, 10), (1.953, 90), (1.566, 60), (1.439, 15), (1.425, 15), (1.337, 40). Xieite is a high pressure polymorph of FeCr₂O₄ and formed by solid-state transformation of chromite under shock-induced high pressure and temperature, in association with other high-pressure minerals including ringwoodite, majorite, lingunite and tuite. The P-T condition for the formation of xieite is estimated to be 18–23 GPa and 1800–1950°C, respectively. Xieite has recently been approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (IMA 2007-056). The mineral name, xieite, is named after Xiande Xie.