This is a 'preproof' accepted article for Mineralogical Magazine. This version may be subject to change during the production process. DOI: 10.1180/mgm.2023.10 Botuobinskite and mirnyite, two new minerals of the crichtonite group included in Cr- pyrope xenocrysts from the Internatsionalnaya kimberlite Dmitriy I. Rezvukhin 1,* , Sergey V. Rashchenko 1,2 , Igor S. Sharygin 1,3 , Vladimir G. Malkovets 1,4 , Taisia A. Alifirova 5 , Leonid. A. Pautov 6,7 , Elena N. Nigmatulina 1 , Yurii V. Seryotkin 1,2 1 – Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, 3 Koptyuga Avenue, Novosibirsk 630090, Russia 2 – Novosibirsk State University, 1 Pirogova Street, Novosibirsk 630090, Russia 3 – Institute of the Earth’s Crust, Siberian Branch of the Russian Academy of Sciences, 128 Lermontova Street, Irkutsk 664033, Russia 4 – ALROSA (Public Joint-Stock Company), 5 Lenina Street, Mirny 678170, Russia 5 – Department of Lithospheric Research, University of Vienna, Josef-Holaubek-Platz 2/UZA2, Vienna 1090, Austria 6 – Fersman Mineralogical Museum of the Russian Academy of Sciences, 18-2 Leninskiy Avenue, 119071 Moscow, Russia 7 – Institute of Mineralogy, South Urals Research Center of Mineralogy and Geoecology, Uralian Branch of the Russian Academy of Sciences, Miass 456317, Russia * Correspondence: m.rezvukhin@igm.nsc.ru, m.rezvukhin@gmail.com ABSTRACT Two new mineral species of the crichtonite group – botuobinskite, ideally SrFe 2+ (Ti 4+ 12Cr 3+ 6)Mg2[O36(OH)2], and mirnyite, ideally SrZr(Ti 4+ 12Cr 3+ 6)Mg2O38, occur as inclusions in mantle-derived Cr-pyrope xenocrysts from the Internatsionalnaya kimberlite pipe, Mirny field, Siberian craton. Botuobinskite forms needle- and blade-like acicular crystals up to 1 mm in length and up to 30 µm in diameter, a large platy inclusion (700x700x80 µm) and roughly isometric grains (up to 80 µm), while mirnyite occurs as needle-and blade-like elongated inclusions (up to 1 mm). Both minerals are jet-black, opaque and exhibit metallic lustre. In plane-polarised incident reflected light, botuobinskite and mirnyite are greyish-white with a weak brownish tint. Between crossed polars, the new species show distinct anisotropy in shades of bluish grey to greenish-brown. Neither bireflectance nor pleochroism is observed. Calculated densities for botuobinskite and mirnyite are 4.3582(5) and 4.3867(3) gm/cm 3 , respectively. The crystal structures of botuobinskite and mirnyite have been refined (R = 0.0316 and 0.0285, respectively) from single crystal X-ray diffraction data. The minerals are trigonal, crystallize in the space group R−3 (No. 148) and are isostructural with other members of the crichtonite group. https://doi.org/10.1180/mgm.2023.10 Published online by Cambridge University Press