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Dmitryivanovite (CaAl2O4) is a newly described, calcium aluminum oxide from the Northwest Africa 470 (NWA470) CH3 chondrite (Ivanova et al. 2002). NWA470 contains abundant small Ca,Alrich inclusions (CAIs), and dmitryivanovite, whose composition is close to stoichiometric CaAl2O4[Ca1.000(Al1.993Si0.003Ti0.002)1.998O4], was found in one of these CAIs. It occurs as ~10 μm subhedral grains intergrown with grossite (CaAl4O7), perovskite, and melilite. Electron backscatter diffraction (EBSD) analysis revealed that dmitryivanovite is a high-pressure polymorph of CaAl2O4(a = 7.95, b = 8.62, c = 10.25 Å, β = 93.1°, space group P21/c, and Z = 12). Dmitryivanovite is the third phase to be described from nature in the binary system of CaO-Al2O3, the other two being hibonite (CaAl12O19) and grossite (CaAl4O7)-all are found in CAIs. The presence of CaAl2O4in NWA470 suggests a local elevated dust/gas ratio in the solar nebula. The phase diagram of CaAl2O4shows that ~2 GPa is required to stabilize the high-pressure CaAl2O4polymorph at 1327 °C, above which CaAl2O4condenses from the solar nebula. Because it is unlikely that the solar nebula ever had such a high total gas pressure, it appears more probable that condensation of the low-pressure polymorph occurred in the solar nebula with an enhanced dust-to-gas ratio and that subsequently the high-pressure polymorph was produced by shock metamorphism, most likely after the CaAl2O4-bearing CAI was incorporated into the NWA470 parent asteroid.

Andreyivanovite (ideally FeCrP) is another new phosphide species from the Kaidun meteorite, which fell in South Yemen in 1980. Kaidun is a unique breccia containing an unprecedented variety of fragments of different chondritic as well as achondritic lithologies. Andreyivanovite was found as individual grains and linear arrays of grains with a maximum dimension of 8 μm within two masses of Fe-rich serpentine. In one sample, it is associated with Fe-Ni-Cr sulfides and florenskyite (FeTiP). Andreyivanovite is creamy white in reflected light, and its luster is metallic. The average of nine electron microprobe analyses yielded the formula Fe(Cr0.587Fe0.150V0.109Ti0.081Ni0.060Co0.002)P. Examination of single grains of andreyivanovite using Laue patterns collected by in situ synchrotron X-ray diffraction (XRD), and by electron-backscatter diffraction revealed it to be isostructural with florenskyite; we were unable to find single crystals of sufficient quality to perform a complete structure analysis. Andreyivanovite crystallizes in the space group Pnma, and has the anti-PbCl2structure. Previously determined cell constants of synthetic material [a = 5.833(1), b = 3.569(1), and c = 6.658(1) Å] were consistent with our XRD work. We used the XPOW program to calculate a powder-XRD pattern; the 5 most intense reflections are d = 2.247 (I = 100), 2.074 (81), 2.258 (46), 1.785 (43), and 1.885 Å (34). Andreyivanovite is the second new phosphide to be described from the Kaidun meteorite. Andreyivanovite could have formed as a result of cooling and crystallization of a melted precursor consisting mainly of Fe-Ni metal enriched in P, Ti, and Cr. Serpentine associated with andreyivanovite would then have formed during aqueous alteration on the parent asteroid. It is also possible that the andreyivanovite could have formed during aqueous alteration; however, artificial FeTiP has been synthesized only during melting experiments, at low oxygen fugacity, and there is no evidence that a hydrothermal genesis is reasonable.