¹Chi Ma,^2,3Alan E. Rubin
American Mineralogist 111, 1186-1191 Link to Article [https://doi.org/10.2138/am-2025-10003]
¹Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125, U.S.A.
²Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, California 90095, U.S.A.
³Maine Mineral & Gem Museum, 99 Main Street, P.O. Box 500, Bethel, Maine 04217, U.S.A.
Copyright: The Mineralogical Society of America

Colomeraite (IMA 2021-061), with an end-member formula NaTi³⁺Si₂O₆, is a new Na pyroxene identified in the Colomera IIE iron meteorite. Colomeraite occurs with albite and K-feldspar in a silicate inclusion. The mean chemical composition of type colomeraite by electron probe microanalysis is (wt%) SiO₂ 54.82, Ti₂O₃ 17.15, TiO₂ 5.58, NaO₂ 12.33, MgO 3.93, FeO 3.59, CaO 1.98, MnO 0.28, Al₂O₃ 0.24, Cr₂O₃ 0.13, K₂O 0.02, total 100.05, giving rise to an empirical formula of (Na_0.88Ca_0.08Mg_0.04)(⁠Mg_0.17Fe_0.11Mn_0.01Al_0.01)Si_2.01O₆, with Ti³⁺ and Ti⁴⁺ partitioned, based on stoichiometry. Colomeraite has the C2/c diopside-type structure with a = 9.70(1) Å, b = 8.88(1) Å, c = 5.30(1) Å, β = 106.8(1)°, V = 437(2) ų, and Z = 4, as revealed by electron backscatter diffraction. The calculated density using the measured composition is 3.36 g/cm³. Colomeraite is a high-pressure and high-temperature Na-Ti³⁺-pyroxene, probably formed from an alkali plagioclase-Ti-rich phase melt via impact mixing of metal and silicates under extremely reducing conditions. The mineral is named after the host meteorite “Colomera.”

^1,2,3Yiping Yang et al. (>10)
American Mineralogist 111, 1036-1045 Link to Article [https://doi.org/10.2138/am-2025-9674]
¹Key Laboratory for Deep Earth Processes and Strategic Mineral Resources, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
²Center for Advanced Planetary Science (CAPS), Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
³Guangdong Provincial Key Laboratory of Mineral Physics and Materials, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
Copyright: The Mineralogical Society of America

Mineral structures record the formation and evolution of the Earth-Moon system. Here we report the discovery of correlated disorder in a silicate mineral kuratite [ideal formula ], which cannot be well documented by classical crystallography, in breccia clasts from near and far sides of the Moon. We employed the advanced three-dimensional electron diffraction (3DED) method in combination with spherical aberration corrected transmission electron microscopy to thoroughly characterize its structural features. The results indicate that the kuratite, coexisting with dendritic pigeonite and ulvöspinel, displays intricate correlated disorder features. These are characterized by alternating arrangements of five correlated site pairs confined within a single disordered layer. The occurrence of a vitrified dendritic pigeonite with similar composition suggests that kuratite formed during the impact-induced melting-cooling processes. This finding shows consistency in impact-driven surface processes between the lunar near and far sides, while demonstrating the utility of advanced nanoscale crystallographic methods for decoding extraterrestrial mineral formation mechanisms.