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.

130 years ago, on November 8, 1895, German physicist Wilhelm Röntgen discovered a new type of radiation, which later became known as X-rays. This discovery quickly gained attention from the scientific community, leading to the development of two models of diffraction when X-rays pass through crystals, which significantly expanded our understanding of the world around us. This discovery played a crucial role in advancing research in mineralogy, chemistry, physics, pharmacology, and other related fields. It is associated with the birth of two of the most important modern sciences: X-ray crystallography and X-ray spectroscopy.

The new high-pressure minerals from meteorites and impact craters can be considered as possible components of the deep-seated Earth’s shells. Obviously they exhibit a definite geophysical interest. The important results of structure studies of high-pressure (HP) minerals, obtained in 20182022, are reviewed. A special attention is addressed to the new structure transformations in Earth’s interior of olivine (asimowite, poirierite), pyroxene (akimotoite, hemleyite) and feldspars (lingunite, liebermanite) related with the crystallization of previously unknown their polymorphic modifications. The intergrowths of poirierite with wadsleyite/ringwoodite in impact chondrites confirm the idea that the transformation of olivine into ringwoodite occurs through formation of poirierite. The structure and composition of new high-pressure minerals from impact regions and meteorites carry information about the complex petrology of deep geospheres, which cannot be manifested in products of laboratory experiments.

There are reviewed important results obtained in the studies of HP-minerals during 2018–2022 years. The emphasis is made on the characterization of HP-polymorphs modifications of olivine (asimovite, poirierite) and wollastonite (breyite and davemaoite) discovered in this period. The structure of poirierite (ε-Mg2SiO4) contains the unique silicate chain Si3O9 with one tetrahedron in its period. Consequently its structural formula is Mg2[SiO3]O, and its intergrowth with wadsleyite/ringwoodite in shocked chondrites support the idea that transformations of olivine into ringwoodite becomes via forming of poirierite. The close ratio of cell parameters in wollastonite (1T) at 8.9 GPa and its synthetic analogue CaGeO3 exhibits the similarity of their structures. The HP/HT data confirm the stability of the wollastonite polymorph (1T, 2M, pseudowollastonite and synthetic analogue of breyite) at the upper mantle conditions. The crystal structures and composition of new НР-minerals discovered as inclusions in diamonds, in meteorites and in the rocks near terrestrial impact craters provide the richer information on the complicate petrology of deep-seated geospheres which cannot be obtained on the base of laboratory experiments.

The new mineral achyrophanite (K,Na)3(Fe3+,Ti,Al,Mg)5O2(AsO4)5 was found in high-temperature sublimates of the Arsenatnaya fumarole at the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, Russia. It is associated with aphthitalite-group sulfates, hematite, alluaudite-group arsenates (badalovite, calciojohillerite, johillerite, nickenichite, hatertite, and khrenovite), ozerovaite, pansnerite, arsenatrotitanite, yurmarinite, svabite, tilasite, katiarsite, yurgensonite, As-bearing sanidine, anhydrite, rutile, cassiterite, and pseudobrookite. Achyrophanite occurs as long-prismatic to acicular or, rarer, tabular crystals up to 0.02 × 0.2 × 1.5 mm, which form parallel, radiating, bush-like, or chaotic aggregates up to 3 mm across. It is transparent, straw-yellow to golden yellow, with strong vitreous luster. The mineral is brittle, with (001) perfect cleavage. Dcalc is 3.814 g cm–3. Achyrophanite is optically biaxial (+), α = 1.823(7), β = 1.840(7), γ = 1.895(7) (589 nm), 2V (meas.) = 60(10)°. Chemical composition (wt.%, electron microprobe) is: Na2O 3.68, K2O 9.32, CaO 0.38, MgO 1.37, MnO 0.08, CuO 0.82, ZnO 0.48, Al2O3 2.09, Fe2O3 20.42, SiO2 0.12, TiO2 7.35, P2O5 0.14, V2O5 0.33, As2O5 51.88, SO3 1.04, and total 99.40. The empirical formula calculated based on 22 O apfu is Na1.29K2.15Ca0.07Mg0.34Mn0.01Cu0.11Zn0.06Al0.44Fe3+2.77Ti1.00Si0.02P0.02S0.14V0.04As4.90O22. Achyrophanite is orthorhombic, space group P2221, a = 6.5824(2), b = 13.2488(4), c = 10.7613(3) Å, V = 938.48(5) Å3 and Z = 2. The strongest reflections of the PXRD pattern [d,Å(I)(hkl)] are 5.615(59)(101), 4.174(42)(022), 3.669(31)(130), 3.148(33)(103), 2.852(43)(141), 2.814(100)(042, 202), 2.689(29)(004), and 2.237(28)(152). The crystal structure of achyrophanite (solved from single-crystal XRD data, R = 4.47%) is unique. It is based on the octahedral-tetrahedral M-T-O pseudo-framework (M = Fe3+ with admixed Ti, Al, Mg, Na; T = As5+). Large-cation A sites (A = K, Na) are located in the channels of the pseudo-framework. The achyrophanite structure can be described as stuffed, with the defect heteropolyhedral pseudo-framework derivative of the orthorhombic Fe3+AsO4 archetype. The mineral is named from the Greek άχυρον, straw, and φαίνομαι, to appear, in allusion to its typical straw-yellow color and long prismatic habit of crystals.

A multimethodic approach based on infrared, Raman, electron spin resonance and photoluminescence spectroscopy, absorption spectroscopy in near infrared, visible and ultraviolet regions, single-crystal X-ray diffraction as well as electron microprobe analyses was applied to the characterization of a new commensurately modulated cubic haüyne analogue with the modulation parameter of 0.2 and unit-cell parameter of 45.3629(3) Å (designated as haüyne-45Å) from the Malobystrinskoe lazurite deposit, in the Baikal Lake area, Siberia, Russia, as well as associated SO32−-bearing afghanite. Haüyne-45Å is the second member, after vladimirivanovite, of the sodalite group with a commensurately modulated structure. The average structure is based on the tetrahedral aluminosilicate sodalite-type framework with sodalite cages of different sizes. The simplified formula of haüyne-45Å is Na6Ca2−x(Si6Al6O24)(SO42−,HS−,S2●−,S4,S3●−,S52−)2−y. The structural modulations of the haüyne-45Å framework are presumably related to the regular alternation of SO42− anions with polysulfide S2●−, S3●−, S4, and S52− groups detected by the spectroscopic methods. Mechanisms of thermal conversions of S-bearing groups in haüyne-45Å under oxidizing and reducing conditions at temperatures up to 800 °C are studied, and their geochemical importance is discussed.

The structural characteristics of minerals that can act as water accumulators in deep geospheres have been studied. Given the vast mass of the Earth’s mantle, even a small amount of water trapped in nominally anhydrous phases of these minerals can significantly exceed the amount of water in the hydrosphere today.

Hydroxylbastn & auml;site-(La), the OH- and La-dominant member of the bastn & auml;site group, in fact known for many years, was studied in detail and has been approved by the IMA-CNMNC as a new mineral species with the ideal, end-member formula La(CO3)(OH). The holotype originates from the Vuoriyarvi (another spelling: Vuorij & auml;rvi) alkaline-ultrabasic complex, Northern Karelia, and the cotype from the Mochalin Log REE deposit, Potaniny Mts, South Urals, both in Russia. At Vuoriyarvi, hydroxylbastn & auml;site-(La) occurs as clusters (up to 1 mm) of light brown, honey-yellow or colourless hexagonal tabular to short-prismatic crystals up to 0.15 mm associated with fluorite and ancylite-(Ce) in cavities of calcite-dolomite carbonatites. At Mochalin Log, hydroxylbastn & auml;site-(La) forms light brown grains up to 0.2 mm included in massive aggregates of other LREE minerals: bastn & auml;site-(Ce), bastn & auml;site-(La), percleveite-(Ce), percleveite-(La), biraite-(Ce), biraite-(La), t & ouml;rnebohmite-(La), ferriperb & oslash;eite-(Ce), allanite-(Ce), etc. Dmeas is 4.75(2) and Dcalc is 4.778 g cm-3 (holotype). Hydroxylbastn & auml;site-(La) is optically uniaxial (+), omega = 1.76(1) and epsilon = 1.86(1) (holotype). The chemical composition (wt.%, electron microprobe, CO2 and H2O calculated: holotype/cotype) is: CaO 0.23/0.00, SrO 0.07/0.00, La2O3 39.47/39.58, Ce2O3 33.51/31.99, Pr2O3 1.03/1.51, Nd2O3 1.95/2.38, F 0.76/3.33, CO2 20.49/20.34, H2O 3.77/2.58, -O=F 0.32/1.40, total 100.96/100.31. The empirical formulae, calculated based on the sum of metal cations of 1 apfu and one CO3 group pfu, are (La0.52Ce0.44Nd0.02Pr0.01Ca0.01)Sigma 1.00(CO3)[(OH)0.90F0.09]Sigma 0.99 (holotype) and (La0.53Ce0.42Nd0.03Pr0.02)Sigma 1.00(CO3)[(OH)0.62F0.38]Sigma 1.00 (cotype). Hydroxylbastn & auml;site-(La) is hexagonal, P6, unit-cell parameters (from powder XRD data, holotype/cotype) are: a = 12.537(3)/12.533(1), c = 9.968(2)/9.908(1) & Aring;, V = 1356.8(5)/1347.9(3) & Aring;3 and Z = 18. Strong reflections of the powder XRD pattern [d,& Aring;(I)(hkl)] are (holotype): 4.98(39)(002), 3.616(88)(300), 2.926(100)(302), 2.089(41)(330), 2.052(46)(304) and 1.927(40)(332). The crystal structure of holotype hydroxylbastn & auml;site-(La) was refined by the Rietveld method, Rwp = 0.0071, Rp = 0.0050, Robs = 0.0466. It is isostructural to hydroxylbastn & auml;site-(Ce) and synthetic bastn & auml;site-type hydroxyl-carbonates REE3+(CO3)(OH) (REE = La-Er), but differs from fluorine-dominant bastn & auml;sites which adopt the space group P62c.

The crystal structure of zharchikhite, AlF(OH) 2 , from the Zharchikhinskoe deposit (Buryatia, Russia) is solved here using single-crystal X-ray diffraction. The mineral is monoclinic, space group P 2 1 /c , a = 5.1788 (4), b = 7.8386 (4), c = 5.1624 (4) Å, β = 116.276 (10)°, V = 187.91 (3) Å 3 and Z = 4. Zharchikhite demonstrates a novel structure type roughly related to the α-PbO 2 structure type and different from other compounds of the Al–F–OH system. The crystal structure of zharchikhite is based on the octahedral pseudoframework built from zigzag chains of edge-sharing AlF 2 (OH) 4 octahedra; adjacent chains are linked via F vertices and the pseudoframework contains wide channels.

The new mineral popugaevaite Ca3[B5O6(OH)6]FCl28H2O was found at the Internatsional'nyi diamond mine, Internatsional'naya kimberlite pipe, Sakha (Yakutia) Republic, Russia. It belongs to the low-temperature hydrothermal mineral assemblage formed in the contact zone between kimberlite and a boron-bearing halite rock. Popugaevaite occurs as veinlets in massive aggregates of ekaterinite and crusts (up to 0.7 mm thick and up to 1 cm x 4 cm in area) on ekaterinite nodules embedded in halite. Other associated minerals are Fe-rich szaib & eacute;lyite, serpentine, dolomite, pyrrhotite and chalcopyrite. Crude prismatic crystals of popugaevaite are up to 0.3 x 1 mm. The mineral is transparent, colourless, with vitreous lustre and perfect {010} cleavage. It is optically biaxial (-), alpha 1.502(2), beta 1.523(2), gamma 1.530(2) and 2Vmeas = 50(10)degrees. The chemical composition (wt.%, electron-microprobe, boron by ICP-MS, H2O calculated by stoichiometry) is: CaO 28.54, B2O3 28.62, F 3.19, Cl 11.50, H2O 32.83, O = (F,Cl) -3.94, total 100.74. The empirical formula, calculated based on 23 O+F+Cl and 22 H atoms per formula unit, is Ca3.07B4.96O6.03(OH)6F1.01Cl1.968H2O. Popugaevaite is monoclinic, space group Pn, a = 8.7055(11), b = 8.1025(11), c = 14.812(2) & Aring;, beta = 91.367(7)degrees, V = 1044.5(2) & Aring;3 and Z = 2. The strongest reflections of the powder X-ray diffraction pattern [d,& Aring;(I,%)(hkl)] are: 8.12(100)(010), 4.058(27)(020), 3.577(15)( $\bar 1$21), 2.936(10)(123), 2.834(16)(301, $\bar 1$05) and 2.283(10)(133). The crystal structure was solved based on single-crystal XRD data and refined on powder data by the Rietveld method, Rwp = 0.0058, Rp = 0.0043 and Robs = 0.0241. Popugaevaite is an isostructural analogue of brianroulstonite Ca3[B5O6(OH)6](OH)Cl28H2O with F- instead of the OH- group non-bound with boron. The structure is based upon the layers of twelve-membered rings of alternating BO3 triangles and BO2(OH)2 tetrahedra. The mineral is named in honour of the Russian geologist Larisa Anatol'evna Popugaeva (1923-1977), one of the principal discoverers of diamondiferous kimberlite pipes in Yakutia.

The new ludwigite-group mineral savelievaite, ideally Mg2Cr3+O2(BO3), was found in the chromitite body at the Malaya Kharamatalou river valley, Voikar-Syninskiy ultrabasic complex, Polar Urals, Russia. Savelievaite and Cr-enriched ludwigite occur in clinochlore veinlets and are associated with earlier magnesiochromite, spinel, chromite, pargasite, diopside, forsterite, serpentine, magnetite and pentlandite. Savelievaite forms prismatic, acicular or fibrous crystals up to 0.05 x 0.4 mm, usually assembled in radiating or chaotic clusters up to 1 x 1.5 mm across. It is opaque, black to greenish-black. The lustre is vitreous for prismatic crystals and silky for fibrous aggregates. D(calc.) = 3.91 g cm-3. Under the microscope in reflected light, savelievaite is grey, non-pleochroic, with weak bireflectance and anisotropism. The chemical composition (wt.%, EMPA, Fe2+:Fe3+ ratio by stoichiometry) is: MgO 34.88, FeO 10.83, NiO 0.36, B2O3 16.80, Al2O3 2.97, V2O3 0.21, Cr2O3 21.97, Fe2O3 12.40, TiO2 0.43, total 100.85. The empirical formula calculated on the basis of 5 O apfu is (Mg1.72Fe2+0.30Ni0.01)Sigma 2.03(Cr3+0.57Fe3+0.31Al0.12Ti0.01V3+0.01)Sigma 1.02B0.96O5. Savelievaite is orthorhombic, space group Pbam, a = 9.2631(6), b = 12.2298(8), c = 3.0104(2) & Aring;, V = 341.04(4) & Aring;3 and Z = 4. The strongest reflections of the powder X-ray diffraction pattern [d,& Aring;(I)(hkl)] are: 5.101(100)(120); 2.551(90)(240); 2.524(88)(201); 2.163(36)(250); and 2.033(55)(321). The crystal structure was solved from single-crystal X-ray diffraction data and refined to R1 = 0.0405. Savelievaite is isostructural with ludwigite, Cr3+ is concentrated at the M4 site. The mineral is named in honour of the Russian petrologist and geologist Dr. Galina Nikolaevna Savelieva (b. 1936). Ludwigite, ideally Mg2Fe3+O2(BO3), and savelievaite form a continuous isomorphous series in which Cr3+ content varies from 0 to 0.60 apfu. Occurrences of Cr-enriched (>1 wt.% Cr2O3) varieties of ludwigite are mainly related to ultrabasic complexes. The Cr-richest (>10 wt.% Cr2O3) ludwigite-savelievaite-series members are found in chromite ores at the Voikar-Syninskiy complex and Volchiegorskoe and Tatishchevskoe deposits, both in the South Urals.

The new mineral calcioveatchite, ideally SrCaB11O16(OH)5·H2O, is a Ca-Sr-ordered analogue of veatchite. It was found at the Nepskoe potassium salt deposit, Irkutsk Oblast, Siberia, Russia in halite-sylvite and sylvite-carnallite rocks, with boracite, hilgardite, kurgantaite, hydroboracite, volkovskite, veatchite, anhydrite, magnesite, and quartz. Calcioveatchite forms prismatic or tabular crystals up to 1 × 1.5 × 3 mm3 and crystal clusters up to 3 mm across. It is transparent and colourless with vitreous lustre. Calcioveatchite is brittle, cleavage is perfect on {010}, the Mohs’ hardness is ca 2, Dmeas is 2.58(1), and Dcalc is 2.567 g cm−3. Calcioveatchite is optically biaxial (+), α = 1.543(2), β = 1.550(5), γ = 1.626(2), 2Vmeas = 30(10)°, and 2Vcalc = 35°. The average chemical composition (wt.%, electron microprobe, H2O calculated by stoichiometry) is: CaO 7.05, SrO 20.70, B2O3 61.96, H2O 10.22, and total 99.93. The empirical formula, calculated based on 22 O apfu = O16(OH)5(H2O) pfu, is Sr1.23Ca0.78B10.99O16(OH)5·H2O. Calcioveatchite is monoclinic, space group P21, a = 6.7030(3), b = 20.6438(9), c = 6.6056(3) Å, β = 119.153(7)°, V = 798.26(8) Å3, and Z = 2. Polytype: 1M. The strongest reflections of the powder XRD pattern [d,Å(I,%)(hkl)] are: 10.35(100)(020), 5.633(12)(110), 5.092(10)(120), 3.447(14)(060), 3.362(13)(101, 051), 3.309(38)(–102), 2.862(10)(012), and 2.585(19)(080). The crystal structure was solved based on single-crystal XRD data, R1 = 0.0420. Calcioveatchite (calcioveatchite-1M) is an isostructural analogue of veatchite-1M with the 11-fold cation polyhedron occupied mainly by Sr [Sr0.902(8)Ca0.098(8)] whereas the 10-fold polyhedron is Ca dominant [Ca0.686(7)Sr0.314(7)]. The chemical composition of veatchite from five localities in Russia (Nepskoe), Kazakhstan (Shoktybay and Chelkar in the North Caspian Region), and the USA (Tick Canyon and Billie Mine in California) was studied, and it is shown to exist in nature as a continuous, almost complete isomorphous series which extends from Ca-free veatchite, Sr2B11O16(OH)5·H2O, to calcioveatchite with the composition Sr1.14Ca0.87B10.99O16(OH)5·H2O.

Materials with high ion mobility are widely used in many fields of modern science and technology. Over the last 40 years, they have thoroughly changed our world. The paper characterizes the structural features of minerals and their synthetic analogs possessing this property. Special attention is paid to the ionic conductors with tetrahedral (zincite- and wurtzite-like), octahedral (ilmenite-like), and mixed (NASICON-like) frameworks. It is emphasized that the main conditions for fast ionic transport are related to the size and positions occupied by a mobile ion, their activation energy, the presence and diameter of conduction channels running inside the structure, isomorphic impurities, and other structural peculiarities. The results of the studies of solid electrolytes are dispersed in different editions, and the overview of new ideas related to their crystal structures was the focus of this paper.

New high-pressure (HP) minerals of impact meteorites can be considered as possible components of deep geospheres. This paper characterizes the structural peculiarities of recently discovered minerals of this genetic type, which are of geophysical interest. Special attention is paid to new data on structural transformations of (Fe,Ti)-oxides with structures of ilmenite and post-spinel phases, HP polymorphs of magnetite, olivine, pyroxenes, and feldspars in deep Earth layers. The structures and composition of new HP minerals from impact zones, meteorites, and diamond inclusions bear information on the complex petrology of deep geospheres, which can be unraveled in laboratory experiments, as well as allowing prediction of their role as possible transporters of large cations in the Earth’s mantle, which affects the thermal regime of the Earth’s interiors.

Strontioborite, which was first described in 1960 and later discredited by the then named Commission on New Minerals and Mineral Names of the International Mineralogical Association (IMA CNMMN), has been re-investigated (electron microprobe, single-crystal and powder X-ray diffraction, crystal structure determination and IR spectroscopy) on two specimens, including the holotype, and revalidated by the IMA Commission on New Minerals, Nomenclature and Classification (CNMNC). Strontioborite is known only at the Chelkar salt dome (North Caspian Region, Western Kazakhstan), in halite rocks with bischofite, magnesite, anhydrite, halurgite, boracite, ginorite and celestine. It forms colourless lamellar, scaly or tabular crystals up to 2 mm across. The chemical composition (wt.%, H2O is calculated for (OH)(4) = 4 H apfu, according to structural data; holotype/neotype) is: CaO 1.42/0.27, SrO 23.10/23.79, B2O3 67.37/67.57, H2O 8.73/8.72, total 100.62/100.37. The empirical formulae [calculated based on 15 O apfu = O-11(OH)(4) pfu] of the holotype and neotype specimens are Sr0.92Ca0.10B7.98O11(OH)(4) and Sr0.95Ca0.02B8.02O11(OH)(4), respectively. The idealised formula is Sr[B8O11(OH)(4)]. Strontioborite is monoclinic, space group P2(1), a = 7.6192(3), b = 8.1867(2), c = 9.9164(3) & Aring;, beta = 108.357(4)degrees, V = 587.07(3) & Aring;(3) and Z = 2. The strongest reflections of the powder X-ray diffraction pattern [d,& Aring;(I)(hkl)] are: 7.22(100)(100), 5.409(61)(110), 4.090(64)(020), 3.300(48)(210), 2.121(30)(24) and 2.043(37)(040, 024, 24). The crystal structure, solved from single-crystal X-ray diffraction data (R = 0.0372), is based upon the (100) layers of polymerised B-O-OH polyanions [B8O11(OH)(4)](2-) and Sr-centred nine-fold polyhedra SrO6(OH)(3). The B-O-OH polyanion is the cluster of three tetrahedra and three triangles; these clusters are decorated by the [B2O2(OH)3] pyro-group consisting of two triangles. The layers are linked via vertices of Sr-centred polyhedra, which share seven vertices with B-centred polyhedra of one layer and two vertices with B-centred polyhedra of the adjacent layer, and by the system of H bonds. The crystal chemistry of strontioborite is discussed in comparison with other natural and synthetic borates.

Single crystals of Ga-, Ge-, and Ga,Ge-rich (up to 41.42 wt% GeO 2 and 33.95 wt% Ga 2 O 3 or 0.98 apfu (atom per formula unit) Ge and 0.90 apfu Ga) and undoped topazes were grown on natural topaz seeds as a newly overgrown layer up to 5 mm thick. The thermogradient hydrothermal method was used at a temperature range of 600 - 650 degrees C and a pressure of 100 MPa under the condition of reverse temperature solubility factor of silica and alumina in the fluoride solution. The chemical composition and crystal structure of the grown topazes, as well as the distribution of gallium and germanium in the overgrown layer, were investigated by electron microprobe analysis (EMPA), single crystal X-ray diffraction (SCXRD) and Raman spectroscopy. The overgrown layers of Ge-, and Ga,Ge-rich topazes have a zonal distribution of elements, two zones corresponding to topaz Al 2 SiO 4 (F,OH) 2 and krieselite (Al,Ga) 2 GeO 4 (F,OH) 2 compositions are distinguished. The structural and spectroscopic studies show linear dependences of unit cell parameters and Raman shift on germanium and gallium contents and confirm the existence of a complete series of topaz-krieselite solid solution.

The paper is devoted to different aspects of new minerals studies and the significance of new minerals in modern science. The most prolific type localities of minerals are briefly overviewed and the role of modern approaches and analytical methods in the studies of new minerals is highlighted. Different implications of recent discoveries are demonstrated on the examples of new mineral species described from peralkaline rocks, volcanic fumaroles, supergene environments, and high-pressure mineral-forming systems in deep geospheres.

Betzite, ideally Na6Ca2(Al6Si6O24)Cl4, a new cancrinite-group mineral, was discovered in a metasomatically altered (pyrometamorphosed) calcic xenolith, hosted by alkaline basalt at the Bellerberg paleovolcano in the Eastern Eifel region, Rhineland-Palatinate, Germany. The associated minerals are anorthite, phlogopite, diopside, grossular, fluorite, calcite, a tobermorite-like mineral, and vanadoallanite-(Ce). Betzite occurs as colorless hexagonal prismatic crystals up to 2 mm long and up to 0.5 mm thick. The new mineral is brittle, with a Mohs' hardness of 5½. Distinct cleavage on {100} and parting on {0001} are observed. The Dmeas = 2.38(2) g/cm3 and Dcalc = 2.363 g/cm3. Betzite is optically uniaxial (+) with ω = 1.528(2) and ε = 1.545(3). The IR spectrum is given. The chemical composition of betzite is (wt.%; electron microprobe, H2O determined by the modified Penfield method): Na2O 11.88, K2O 4.82, CaO 10.74, MgO 0.21, Al2O3 27.32, Fe2O3 0.68, SiO2 32.84, SO3 1.89, Cl 10.48, H2O 1.10, −O≡Cl −2.37, total 99.59. The empirical formula is Na4.22K1.13Ca2.11Mg0.06(Si6.01Al5.90Fe3+0.09O24)Cl3.25(SO4)0.26(H1.34O0.64). The crystal structure was determined using single-crystal X-ray diffraction data. It is hexagonal, space group P63, a = 12.8166(9) Å, c = 5.3562(3) Å, V = 761.95(12) Å3 (at a temperature of 100 K) and Z = 3. Betzite is a dimorph of quadridavyne, with a disordered distribution of extra-framework components occupying channels. The strongest lines of the powder X-ray diffraction pattern [d, Å (I, %) (hkl)] are: 11.14 (31) (100), 4.833 (93) (101), 3.715 (95) (300), 3.313 (100) (211), 2.787 (37) (400), 2.681 (56) (002, 131), 2.474 (35) (112, 401), 2.146 (24) (330). The mineral is named in honor of the German amateur mineralogist Volker Betz (b. 1947).

Unusual chemical and structural varieties of two lovozerite-group minerals from the Lovozero alkaline complex (Kola Peninsula) were studied by means of electron microprobe analysis, single-crystal X‑ray diffraction, and IR spectroscopy. The Zr- and Fe-rich variety of kazakovite with the composition Na 6.20 U 0.01 (H 3 O) 0.25 (Mn 0.72 Ca 0.10 ) Σ0.82 (Ti0 .61 Zr 0.18 ) Σ0.97 Si 6 O 17.83 (OH) 0.17 was found in the Palitra pegmatite body, Mt. Kedykverpakhk. The mineral is trigonal, R 3 m , a = 10.2622(5), с = 13.0884(7) Å, V = 1193.71(13) Å 3 ; R hkl = 0.0383. The variety of trigonal litvinskite from Mt. Alluaiv is characterized by the lowest total content of large cations sum (Na, Ca, and Mn) and the space group previously unknown for this mineral R 3 m . Its composition is Na 2.05 (H 2 O) 0.64 (Mn 0.13 Ca 0.02 ) Σ0.15 (Zr 0.93 Ti 0.06 Fe_0.02^3 + ]) Σ1.01 Si 6 O 12.36 (OH) 5.64 , and unit cell parameters are: a = 10.1880(10), с = 13.1209(16) Å, V = 1179.4(3) Å 3 ; R hkl = 0.0665. The presence of hydronium H 3 O + was first revealed for lovozerite-group minerals. The possibility of formation of kapustinite and litvinskite as a result of the step-by-step townendite alteration process (decationization with the replacing of the corresponding part of O 2– by OH – ) is discussed.

General characteristics of the crystal-chemical features of the sulfide class of minerals, including the genesis, chemical bonding, different approaches to the classification, etc., are given. The structures of the main representatives of tetrahedral sulfides, disulfides, cluster sulfides, sulfides of elements with incomplete valence shells, and sulfosalts are considered. Mineralogically possible iron sulfides in the Earth’s core are presented. It is noted that the geophysical interest in sulfide Fe5S2 is related to its possible presence in the core of not only the Earth but also in the other planets in the solar system.