Vol CLII, No 3 (2023)

This paper is devoted to the olivine pseudomorphization processes occurring in basalt under the action of high-temperature O₂-rich gas in oxidizing-type fumaroles at the Tolbachik volcano (Kamchatka, Russia). The alteration of olivine with composition Fo_72–90 in a terraneous oxidizing-type exhalation system involves two independent processes: (1) oxidative breakdown (above 600 °C) with the formation of forsterite Fo_90–100 together with hematite, magnesioferrite, and, presumably, “magnesian laihunite”; (2) replacement by mineral aggregates in which pyroxenes [enstatite, clinoenstatite, diopside, aegirine-augite (Ca_0.5Na_0.5)(Mg_0.5Fe_0.5)Si₂O₆], low-alumina fluoromagnesian micas (yangzhumingite and fluorotetraferriphlogopite), chondrodite or cristobalite are the main components accompanied by hematite, sometimes with magnesioferrite or tenorite. In the active Arsenatnaya fumarole, the change of the main Si minerals in pseudomorphs with the gas temperature decrease occurs in a sequence that generally reflects an increase in the degree of condensation of tetrahedral Si-O motifs: olivine (forsterite) → orthopyroxene (enstatite) → clinopyroxenes → micas → cristobalite.

The principal specific features are considered for new minerals discovered during the period 2014–2021 and nominated as winners of their competition “Mineral of the Year” announced by the IMA in 2014. The corresponding publications contain the detailed description of phenomena complicating the real structure (merelaniite), the uncommon combination of chemical elements (seaborgite), fragments of compounds previously known only in synthetic nonorganic phases (ophirite, chanabayaite, bojarite). The special attention is focused upon the indicative role of these minerals for reconstruction of physical-chemical conditions accompanying their crystallization, as well as to their position in corresponding transformational-genetic series. There is proposed the crystal growth model of the new W-bearing mineral tewite, which has been proved experimentally.

A study of composition of minerals (major and rare-earth elements) of clinozoisite amphibolites closely associated with corundum-bearing rocks at the Khitoostrov occurrence (North Karelia) was carried out. The clinozoisite amphibolites contain ferruginous phlogopite containing more Al than the ferruginous phlogopite in the host garnet amphibolites; calcium amphibole belongs to the chermakite–pargasite–sadanagaite series; the basic plagioclase which is absent in the host rocks, and margarite. Reactionary relationships of minerals are noted – plagioclase-amphibole symplectites around garnet porphyroblasts, development of clinozoisite after calcium amphibole. Some of the minerals (clinozoisite, calcium amphibole) acquire rare-earth elements (REE) distribution spectra that are uncharacteristic for them, inheriting them from substitutable minerals in the areas of distribution of reaction structures: calcium amphibole inherits the spectrum of garnets, and clinozoisite inherits the spectrum of calcium amphibole. The hypothesis of metasomatic origin of clinozoisite amphibolites and the redistribution of REE under the influence of fluid are discussed.

The atomic force microscopy has allowed to register in experiments the development of a screw dislocation on surface of the growing dioxidine crystal triggered by input of tourmaline particles as solid impurities. For theoretical explanation of the process, there is proposed a three-stage mechanism assuming the (1) relaxation of stresses around the impurity particle through formation of one or more dislocations before its germetization at the first stage, then (2) additional formation of boundary dislocations in the moment of the particle been sealing by a growth layer at the second stage, and (3) appearance of the resulting dislocation after complete sealing of the impurity at the third stage. Thus, for the first time the phenomenon of dislocation propagating through growth layers was registered in nanoscale.

The oxidation state of Fe, Cu, Eu, Ce, etc. in minerals is an important indicator of redox conditions for their formation and evolution. In this work, the features of X-ray emission Fe L_α,β spectra (XES) obtained by Cameca SX100 microprobe, as well as the Mössbauer spectra of Cr-spinels of various compositions from a number of the Urals ultramafic massifs, have been studied. Using microprobe data on the composition and homogeneity of the grains, as well as the Fe³⁺/\({\text{Fe}}_{{{\text{tot}}}}^{{{\text{M\"o ssb}}}},\) 19 intralaboratory reference samples have been selected from a large number of the Urals Cr-spinels. Based on the analysis of BSE images and maps of the distribution of elements in Cr-spinel grains, the most homogeneous ones were identified. It was shown that, up to the determination error, Fe³⁺/\({\text{Fe}}_{{{\text{tot}}}}^{{{\text{M\"o ssb}}}}\) coincides with that obtained in the framework for calculation approach based on microprobe data on the composition and assumptions about the mineral stoichiometry. For determination of Fe oxidation state by XES data, it has been proposed to use as a calibration dependence for intralaboratory reference samples the position of the maximum of Fe L_α line on the content of Fe²⁺; the latter is satisfactorily approximated by a linear function (r_xy = 0.96); the relative error of Fe²⁺ determination is 2%. Approbation of the developed approach was carried out on a series of control samples of Cr-spinels; the obtained values of Fe²⁺ and Fe³⁺/Fe_tot agree satisfactorily with the Mössbauer and calculated data in the stoichiometric approximation.

For the first time the article publishes letters of A.E. Fersman (November 1938–February 1945) and E.M. Fersman (August 1945–January 1964) from archive of D.P. Grigoriev stored in the Russian Mineralogical Society, and memories of V.N. Florovskaya about meetings with A.E. Fersman (1937–1945) and P.N. Chirvinsky (1937–1954) at the Afrikanda deposit, the Tietta scientific station in Khibiny and later in Moscow, Leningrad, Perm. The publication is timed to the 140th anniversary of the A.E. Fersman date of birth. Attention is drawn to the importance of preserving and researching personal archives when studying the history of science.

The article contains an overview of reports and master classes at the International Diamond School, which took place in February 20–25, 2023 in Bressanone, Italy. The School touched upon such aspects of the study of natural diamonds as geochemical and isotope features and morphology of crystals, composition of inclusions in them, geological conditions of formation, as well as interesting debatable issues.