Tistarite, Ti2O3, a new refractory mineral from the Allende meteorite

Chi Ma & George R. Rossman

Division of Geological and Planetary Sciences
California Institute of Technology
Pasadena, CA 91125-2500, USA


Tistarite, ideally Ti2O3, is a new member of the corundum-hematite group. It is found as one subhedral crystal in a cluster of micrometer-sized refractory grains along with khamrabaevite (TiC), rutile, and corundum crystals within a chondrule from the Allende meteorite. The mean chemical composition determined by electron microprobe analysis is (wt%) Ti2O3 94.94, MgO 2.06, Al2O3 1.50, ZrO2 0.44, FeO 0.24, CaO 0.10, Cr2O3 0.06, sum 99.34. The empirical formula calculated on the basis of 3 O atoms is (Ti3+1.90Mg0.07Al0.01Zr0.01)Σ2.02O3. Tistarite is rhombohedral, R-3c; a = 5.158 Å, c = 13.611 Å, V = 313.61 Å3, and Z = 6. Its electron back-scatter diffraction pattern matches that of synthetic Ti2O3 with the R-3c structure. The strongest calculated X-ray powder diffraction lines from the synthetic Ti2O3 data are [d spacing in Å (I) hkl]: 3.734 (84) (012), 2.707 (88) (104), 2.579 (90) (110), 2.242 (38) (113), 1.867 (33) (024), 1.703 (100) (116), 1.512 (28) (214), 1.489 (46) (300), 1.121 (20) (226), 0.896 (25) (416). The mineral is named after the composition “Ti” and the word “star,” implying that this new refractory mineral is among the first solids formed in the solar system.  

pronounciation:  tie-star'-ite

Reflected light photomicrograph of tistarite that has its top half with a residual coating of carbon after the electron microprobe analysis.
Backscattered electron image of the same tistarite in the SEM.

Raman spectral data for tistarite

American Mineralogist 93, 154-157