Vol CLII, No 1 (2023)

The article is devoted to the 250th anniversary of the first higher technical educational institution in Russia – Saint Petersburg Mining University (Mining Institute), whose students and scientific schools made a great contribution to the development of mining and geological sciences and ensured the formation of the mineral resource base of Russia. The main stages of the glorious history of the Mining Institute from its foundation in 1773 to the present day are described. The constant close relationship with the Mining Institute of the Russian Mineralogical Society was emphasized. The Presidium and library of RMS has been located within the walls of the Institute for 154 years and where meetings and congresses of the Society are invariably held.

The new ixiolte-group mineral nioboixiolite-(Mn²⁺), ideally \( \left( {{\text{N}}{{{\text{b}}}_{{{2 \mathord{\left/ {\vphantom {2 3}} \right. } 3}}}}{\text{Mn}}_{{{1 \mathord{\left/ {\vphantom {1 3}} \right. } 3}}}^{{2 + }}} \right){{{\text{O}}}_{{\text{2}}}}{\text{,}} \) the niobian analogue of ixiolite-(Mn²⁺), was discovered in the Sosedka granitic pegmatite vein, Malkhan pegmatite field, Zabaikalsky Krai (Transbaikal Region), Siberia, Russia. The associated minerals are albite, quartz, microcline, elbaite, beryl, bismuthinite, euxenite-(Y), zircon, rutile, cassiterite, and cannonite. Nioboixiolite-(Mn²⁺) occurs as clusters of dark brown to brown-black prismatic crystals up to 0.8 × 1.5 × 5 mm embedded in albite. The lustre is submetallic to adamantine, and the streak is brown. Cleavage is not observed. The Mohs’ hardness is 4.5–5. Density calculated using the empirical formula is equal to 5.803 g cm^–3. The IR spectrum and reflectance spectra in visible range are given. The chemical composition of nioboixiolite-(Mn²⁺) is (electron microprobe, wt %): MnO 14.94, Sc₂O₃ 1.80, Fe₂O₃ 0.20, Y₂O₃ 1.34, TiO₂ 7.66, ZrO₂ 1.74, SnO₂ 1.01, ThO₂ 0.26, UO₂ 1.44, Nb₂O₅ 42.80, Ta₂O₅ 26.77, total 99.96. The empirical formula is (Nb_1.59\({\text{Mn}}_{{1.04}}^{{2 + }}\)Ta_0.59Ti_0.47Sc_0.13Zr_0.07Y_0.06Sn_0.03U_0.03\({\text{Fe}}_{{0.01}}^{{3 + }}\))_Σ4.02O₈ (Z = 1). The crystal structure was determined using single-crystal X-ray diffraction data and refined to R = 0.0474. The new mineral is isostructural to other ixiolite-group members. Nioboixiolite-(Mn²⁺) is orthorhombic, space group: Pbcn, a = 4.762(2) Å, b = 5.739(1) Å, c = 5.149(1) Å, V  =  140.7(1) ų. The strongest lines of the powder X-ray diffraction pattern [d, Å (I, %) (hkl)] are: 3.662 (29) (110), 2.984 (100) (111), 2.505 (21) (021), 1.775 (21) (130), 1.748 (28) (202), 1.726 (35) (221), 1.553 (20) (113), 1.473 (19) (023), 1.463 (30) (311, 132).

Native cobalt was found in amphibolite of the Kola ultra-deep borehole (SG-3) from a depth of 9630 m by a complex of local analytical methods (analytical scanning electron microscopy, EBSD). The studied amphibolite is a fine-grained melanocratic rock composed mainly of magnesio-ferri-hornblende and containing accessory native-metal, telluride, sulphotelluride and sulphide (Au, Ag, Pd, Bi, Cu, Pb, Zn, Sb, Fe) mineralization. It includes a clinopyroxene xenoclast which poor in sulphides and including native cobalt. The absence of any significant impurity in native cobalt and its belonging to the hexagonal α-modification was determined. Native cobalt was formed probably before both the stage of retrograde metamorphism with the hydrothermal alteration of amphibolite and the formation of the volcano-sedimentary protolith of this rock. Native cobalt probably belongs to the early high-temperature mineral phases inherited from the older Proterozoic-Archean basic volcanism, while the time of formation of this layer of amphibolites is 2.4 billion years.

Olivine group minerals were formed in melilite-nepheline paralavas in two combustion metamorphic (CM) complexes as result of thermal alterations of sedimentary rocks caused by multistage current and quaternary wild coal fires. Products of decomposition of the olivine solid solution into Ca-bearing fayalite and kirschsteinite have been found in paralavas of the Khamaryn–Khural–Khiid CM complex. And, besides these two minerals, forterite–fayalite, monticellite–kirschsteinite and simplectite intergrowths of kirschsteinite with nepheline were detected in paralavas of the Nyalga PM complex. Olivines are differing by their textural features, index value Mg# = Mg/(Mg + Fe) and their crystallization temperature as a consequence of local variations of formation conditions and composition of silica-undersaturated Ca-rich mafic initial melts of melilite–nepheline paralavas. Olivines of the monticellite–kirschsteinite series containing up to 86 mol. % of kirschsteinite end-member occur only in paralavas containing xenoliths of thermally modified carbonate–silicate sedimentary rocks. Crystallization of these olivines together with gehlenitic melilite took place in the process of reactionary interaction between mafic paralava melts and xenoliths of marly limestones with large variations in contents of silicate (clay–feldspar) admixture.

Fluoborite has been for the first time discovered in magnetite-bearing skarns at the distance of few meters from the contact between dolomite-carbonate and granodiorite of the Aktash deposit. Fluoborite, Mg₃(BO₃)(F,OH)₃, was revealed and studied with optical and electron microscopy and determination of its chemical composition (wt %): MgO 63.29–64.56, F 18.35–21.91, B₂O₃ 18.44–18.58, H₂O 4.02–5.62, –O=F₂ 7.73–9.23, total 99.27–99.85. The identity of the mineral has been confirmed by X-ray phase analysis (reflections 7.702, 4.445, 3.584, 2.908, 2.417, 2.22, 2.133, 1.806, 1.763, 1.678, 1.635, 1.554, 1.534, 1.485, 1.477 Å) and Raman spectroscopy (Raman spectra with bands 952, 848, 534, 423, 345, 239 and 175 cm^–1). Radial-columnar aggregates of fluoborite occurring in serpentine are partially replaced by fluorite, and some tops of its crystals are overgrown by magnetite metacrystals. These magnetite metacrystals contain poikilites of fluoroborite and fluorite.

The article is dedicated to the 250th anniversary of the St. Petersburg Mining University (Mining Institute). History of the Mining University is closely connected with the names of scientists who have made a huge contribution to the development of mineralogy and adjacent sciences. The names of 57 alumni and staff members of the Institute have forever entered the history of mineralogy. 62 mineral species are named in their honor. The article summarizes the scientific interests and achievements of teachers, scientists and mining engineers, after whom the minerals were named.