Abstract

Kangite (IMA 2011-092), (Sc,Ti,Al,Zr,Mg,Ca,□)2O3, is a new scandia mineral, occurring as micrometer-sized crystals with REE-rich perovskite and spinel in a davisite-dominant ultra-refractory inclusion from the Allende CV3 carbonaceous chondrite. The phase was characterized by SEM, EBSD, synchrotron micro-Laue diffraction, micro-Raman, and EPMA. The mean chemical composition of the type kangite is (wt%) TiO2 36.6, Sc2O3 26.4, ZrO2 11.3, Al2O3 7.0, Y2O3 5.4, CaO 3.9, MgO 3.14, Dy2O3 1.8, SiO2 1.7, V2O3 1.31, Er2O3 0.92, FeO 0.8, Gd2O3 0.60, Ho2O3 0.40, Tb2O3 0.18, Cr2O3 0.09, ThO2 0.04, O −0.3, sum 101.28, which leads to an empirical formula calculated on the basis of 3 O atoms of [(Sc0.54Al0.16Y0.07V0.03Gd0.01Dy0.01Er0.01)3+∑0.83(Ti0.66Zr0.13)4+∑0.79(Mg0.11Ca0.06 Fe0.02)2+∑0.190.19] ∑2.00O3. Synchrotron micro-Laue diffraction (i.e., an energy scan by a high-flux X-ray monochromatic beam) on one type domain at submicrometer resolution revealed that kangite has a cation-deficient Ia3̄ bixbyite-type cubic structure. The cell parameters are a = 9.842(1) Å, V = 953.3(1) Å3, Z = 16, which leads to a calculated density of 3.879 g/cm3. Kangite is a new ultra-refractory mineral, likely originating through low-temperature oxidation of a Sc-,Ti3+-enriched high-temperature condensate oxide dating to the birth of the Solar System.

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