Том CLIV, № 3 (2025)

Data on the chemical composition of surface and pore brines of 10 salt lakes of the Crimean Peninsula belonging to the Yevpatoria group are presented. Using the method of thermodynamic modeling, saturation indices for calcium and magnesium carbonates, gypsum, and halite were calculated and their dependence on the total salinity of brines was established. According to the modeling results and taking into account the chemical composition of brines, calcite and gypsum deposition is most likely in the least salty lakes (Bogaily, Moynaskoye, and Oburgskoye ones), and calcite, aragonite, dolomite, magnesite, gypsum, and halite deposition is possible in the saltiest lakes (Sasyk-Sivash, Airohi, Galgasskoye, and Terekii ones). Lakes Sakskoye, Aji-Baychi, and Konradskoye are characterized by an intermediate position in terms of brine salinity and a set of minerals, the deposition of which is possible from surface and pore brines.

The article presents the results of studies of the mineralogy of the ores of the poorly studied gold-antimony Krokhalinoye deposit (dyke type), located on the southeastern flank of the Yana-Kolyma orogenic belt. Sulfide mineralization is represented mainly by stibnite, arsenopyrite and pyrite, less often jamesonite and berthierite are noted; of the gold minerals, high-fineness native gold, aurostibite, electrum and "mustard" gold (auroantimonate) are present. The native gold of the deposit is the highest-fineness of all known deposits of the Central Kolyma region.

Fredrikssonite, a Mn³⁺-dominant oxoborate of the ludwigite group, has been found in exhalations of the Arsenatnaya fumarole at the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, Russia. Earlier this mineral was known only in Mn-enriched skarnoids of the Filipstad ore district in Sweden. In the Arsenatnaya fumarole, Fredrikssonite occurs as reddish-rufous long-prismatic and acicular crystals up to 0.05 mm long in sublimate incrustations formed at temperatures not lower than 550 °C, in association with anhydrite, minerals of the berzelite-schäferite series, svabite, tilasite, calciojohillerite, magnesioferrite, hematite, Mn³⁺-containing ludwigite, rhabdoborite-group borates, diopside, forsterite, and powellite. Tolbachik fredrikssonite is represented by the Fe³⁺-richest variety known today, almost free of Fe²⁺ and Mn²⁺. Its chemical composition (wt.%): 40.96 MgO, 0.28 CuO, 26.57 Mn₂O₃, 13.03 Fe₂O₃, 17.78 B₂O₃, 1.41 As₂O₅, total 100.63; the empirical formula calculated based on 5 O atoms per formula unit is: (Mg_1.97Cu_0.01)_∑1.98(Mn³⁺_0.65Fe³⁺_0.33)_∑0.99[B_0.99As_0.02O₃]O₂. The parameters of the orthorhombic (space group Pbam) unit cell are: a = 9.2078(12), b = 12.4458(13), c = 2.9812(3) Å, V = 341.64(7) ų. The crystal structure of fredrikssonite from the Arsenatnaya fumarole is solved on a single crystal (R = 6.95%); it is isostructural to other members of the ludwigite group. The formation conditions of Mn³⁺-rich oxoborates of this group are discussed.

The previously published data on S₂^•–-containing minerals of the sodalite, cancrinite and scapolite groups are summarized, and new data on the S₂^•– radical anion in haüyne with a commensurate modulated structure and in vesuvianite are presented. It is shown that the S₂^•– radical anion is quite widespread as an impurity in these minerals, affecting their colour as yellow chromophore, as well as such physical properties as luminescence, ESR, Raman and optical electronic spectra in the visible, near IR and UV regions. It is concluded that the S₂^•– radical anion plays an important role in the geochemistry of sulfur and can be considered as an informative geochemical marker.

This work presents the results of a study of the microstructure of mammoth tusk (MT) samples Mammuthus Primigenius using scanning electron microscopy. Dependence of the tusk tissue strength on the characteristics of the crack formation and mineralization was determined. It was found that MT tissues are characterized by the presence of microcracks, the number of which increases with a decrease in the quality of the substantial. It is shown that the anisotropy of the tusk properties, due to the specific framework mineral-organic structure, decreases with an increase in the number of microcracks. It was revealed that the dentin of the tusks is characterized by an uneven distribution of calcium and magnesium ions, indicating the occurrence of mineralization processes accompanied by the transformation and saturation of tissues with magnesium-containing minerals, which was confirmed by the results of X-ray phase analysis, which showed the presence of newberyite (Mg(PO₃OH) · 3H₂O) in the sample. The nature of foreign inclusions can also indicate the environment in which the tusk was found before its discovery, or the introduction of mineral particles into the body of the tusk during the life of the animal.