Discovery of Rubinite, Ca_3Ti^(3+)_2Si_3O_(12), a new Garnet Mineral in Refractory Inclusions from Carbonaceous Chondrites

Abstract

During a nanomineralogy investigation of carbonaceous chondrites, a new Ti^(3+)-dominant garnet, named "rubinite," Ca_3Ti^(3+)_2Si_3O_(12) with the Ia^3d garnet structure, was identified in five Ca-Al-rich inclusions (CAIs) from the CV3 chondrites Vigarano, Allende, and Efremovka. Field-emission scanning electron microscope, electron back-scatter diffraction, electron microprobe and ion microprobe techniques were used to characterize the chemistry, oxygen-isotope compositions, and structure of rubinite and associated phases. Synthetic Ca_3Ti^(3+)_2Si_3O_(12) garnet was reported by [1]. Here, we describe the first natural occurrences of rubinite as a refractory mineral in primitive meteorites. The mineral has been approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (IMA 2016-110) [2]. The name honors Alan E. Rubin, a cosmochemist at University of California, Los Angeles (UCLA), USA, for his many contributions to cosmochemistry and meteorite research.

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