Xieite,a new mineral of high-pressure FeCr_2O_4 polymorph

Xieite,a new mineral,occurs in the shock vein of the Suizhou meteorite.The mineral has an ortho-rhombic structure and its space group is Bbmm.The cell parameters are a = 9.462(6),b = 9.562(9),c = 2.916(1).The crystal-chemical formula is(Fe0.87Mg0.13Mn0.01)1.01(Cr1.62Al0.25Ti0.08V0.02)1.97O4,or simply formula FeCr2O4.Stronger X-ray diffraction lines are [d(),I/Io]:(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 tem-perature,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℃,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.

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） A, b = 9.562（9） A, c = 2.916（1）A. The crystal-chemical formula is （Fe0.87Mg0.13Mn0.01）1.01（Cr1.62AI0.25Ti0.08V0.02）1.97O4, or simply formula FeCr2O4. Stronger X-ray diffraction lines are [d （A）, I/Io]： （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-Tcondition for the formation of xieite is estimated to be 18--23 GPa and 1800--1950℃, 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.