¹Chi Ma,²Alexander N. Krot,¹Julie Paque,³Oliver Tschauner,¹Kazuhide Nagashima
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13771]
¹Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, 91125 USA
²Hawai‘i Institute of Geophysics and Planetology, University of Hawai‘i at Mānoa, Honolulu, Hawai‘i, 96822 USA
³Department of Geoscience, University of Nevada, Las Vegas, Nevada, 89154 USA
Published by arrangement with John Wiley & Sons

Beckettite (Ca2V6Al6O20; IMA 2015-001) is a newly discovered refractory mineral, occurring as micrometer-sized grains intergrown with hibonite and perovskite, and surrounded by secondary grossular, anorthite, coulsonite, hercynite, and corundum. It occurs within highly altered areas in a V-rich, Type A Ca-Al-rich inclusion (CAI), A-WP1, from the Allende CV3 carbonaceous chondrite. The type beckettite has an empirical formula of (Ca1.99Na0.01)(V3+3.47Al1.40Ti4+0.57Mg0.25Sc0.08Fe2+0.04)(Al5.72Si0.28)O20, with a triclinic structure in space group Purn:x-wiley:10869379:media:maps13771:maps13771-math-0001 and cell parameters a = 10.367 Å, b = 10.756 Å, c = 8.895 Å, α = 106.0°, β = 96.0°, γ = 124.7°, V = 739.7 Å3, and Z = 2, which leads to a calculated density of 3.67 g cm−3. Beckettite’s general formula is Ca2(V,Al,Ti,Mg)6Al6O20 and the endmember formula is Ca2V6Al6O20. Beckettite is slightly 16O-depleted (Δ17O = −16 ± 2‰) compared to the coexisting hibonite and spinel −24 ± 2‰. Beckettite is a primary high-temperature mineral resulting from igneous crystallization of an 16O-rich V-rich CAI melt together with V-bearing hibonite, perovskite, burnettite, spinel, and paqueite. Subsequently, beckettite experienced an incomplete isotope exchange with an 16O-poor aqueous fluid (Δ17O = −3 ± 2‰) on the Allende parent asteroid.