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The new ettringite-group mineral chiyokoite, ideally Ca3Si(CO3)[B(OH)4]O(OH)5·12H2O, was found in a hydrothermally altered calc-silicate skarn at the Fuka mine, Okayama Prefecture, Japan. Associated minerals are calcite, henmilite, and tacharanite. Chiyokoite occurs as hexagonal prismatic crystals up to 30 μm long and up to 20 μm thick. The major forms are the hexagonal prism {100} and monohedra {0001} and {000}. The crystals are combined in clusters which form friable nests up to 1 cm across. The mineral is pink to colorless with white streak and vitreous luster. The cleavage is parallel to {100} and {0001}, good. The fracture is stepped. Dmeas is 1.85(1) g/cm3, Dcalc is 1.85 g/cm3. Chiyokoite is optically uniaxial (–), ω = 1.523(2) and ε = 1.492(3) (589 nm). The infrared spectrum is reported. The chemical composition (wt.%) is CaO 27.56, B2O3 3.47, Al2O3 3.05, Fe2O3 0.12, As2O3 4.77, MnO2 0.32, SiO2 6.55, SO3 0.76, H2O 46.3, CO2 7.30, total 100.2. The empirical formula calculated on the basis of 3 Ca apfu is H31.37Ca3(Si0.67Al0.37Mn4+0.02Fe3+0.01)Σ1.07(C1.01B0.61As3+0.29S0.06)Σ1.97O24.19. The simplified general formula is Ca3(Si,Al)(CO3,AsO3)[B(OH)4,AsO3](OH)6·12H2O. Chiyokoite is hexagonal, P63, a = 11.0119(5), c = 10.5252(6) Å, and V = 1105.3(1) Å3. The strongest reflections of the powder X-ray diffraction pattern [d,Å(I)(hkl)] are: 9.53(100)(100), 5.50(24)(110), 4.618(11)(102), 3.812(23)(112), 3.412(15)(211), 2.726(14)(302), 2.521(19)(123), and 2.172(13)(320,402,223). The crystal structure, refined from single-crystal X-ray diffraction data [R1(F) = 0.042], is based on [Ca3(Si,Al)(OH)6(H2O)12] columns parallel to the c axis with B(OH)4– and CO32– and admixed AsO33– anionic groups in channels between the columns. The mineral is named in honor of Professor Chiyoko Henmi (1949–2018).

A new mineral falgarite, K4(V+4O)3(SO4)5 was discovered at the tract of Kukhi-Malik, Fan-Yagnob coal deposit, ca. 75 km N of Dushanbe, Tajikistan. The new mineral is named after the Falgar, an ancient Sogdian name for an area around the Zeravshan riverhead. Falgarite is a fumarolic mineral formed directly from a gas emitted by a natural underground coal fire. Associated minerals are anhydrite, baryte, molybdite, an unidentified Tl-vanadyl sulfate, K–Mg sulfate and an anhydrous Mg-sulfate. Falgarite forms small isometric or pseudo-octahedral individual crystals (10–60 μm) of turquoise colour and spherical aggregates up to 0.5 mm in diameter. Mohs hardness is ~ 2.5, Dmeas = 2.87(2) and Dcalc = 2.89 g/cm3. Refractive indices are: α = 1.588(3), β(calc.) = 1.600(3) and γ = 1.609(2) (590 nm). In transmitted light falgarite is transparent green with a weak pleochroism. The mineral is non-soluble in H2O and 5% HNO3 at room temperature. Infrared spectra support the absence of H2O and OH–. The chemical composition determined by electron-microprobe analysis is (wt.%): Na2O 0.55, K2O 20.76, Tl2O 1.83, VO2 29.38 and SO3 46.78, total 99.29. The empirical formula (based on 23 O apfu) is: (K3.76Na0.15Tl0.07)Σ3.98V3.02S4.99O23.0. The strongest lines of the powder X-ray diffraction pattern are [d,Å(I,%)(hkl)]: 3.20(70)(202); 3.17(80)024; 3.14(70)$\bar{2}$04; 3.01(50)$\bar{1}$51; and 2.88(100)151. Falgarite is monoclinic, P21/n, a = 8.7209(5), b = 16.1777(6), c = 14.4614(7) Å, β = 106.744(5)°, V = 1953.77(17) Å3, Z = 4 and R1 = 0.05. VO6 octahedra and SO4 tetrahedra link together by sharing corners thus forming a [(VO)3(SO4)5]4– framework. K+, Na+ and Tl+ cations are located in the channels of the framework. The synthetic K4(VO)3(SO4)5 analogue is known.

The new sulfate mineral ferroefremovite, ideally (NH4)2Fe2+2(SO4)3, was discovered at the “Bocca Grande” fumarole, Solfatara di Pozzuoli, Flegrean Volcanic Complex, Naples Province, Campania, Italy. Associated minerals are adranosite, adranosite-(Fe), godovikovite, huizingite-(Al), mascagnite, and opal. Ferroefremovite forms cubic crystals up to 0.1 mm across. The new mineral is colorless and has a vitreous luster and white streak. It is brittle and has an uneven fracture. No cleavage or parting are observed. Mohs hardness is 2. Dmeas. = 2.69(1) g/cm3. Dcalc. = 2.700 g/cm3. Optically, ferroefremovite is isotropic, n = 1.574(3) (λ = 589 nm). It is non-pleochroic. The presence of the NH4+ cation is confirmed by the Raman spectrum. The chemical composition of ferroefremovite is (wt.%; electron microprobe, N determined by CNH analysis) (NH4)2O 11.51, Na2O 0.11, K2O 1.35, MgO 8.38, MnO 0.98, FeO 18.94, SO3 57.08, total 98.35. The empirical formula based on 12 O apfu is [(NH4)1.85K0.12Na0.01]Σ1.98(Fe2+1.11Mg0.87Mn0.06)Σ2.04S2.99O12. Ferroefremovite is cubic, space group P213, with a = 10.0484(9) Å, V = 1014.59(16) Å3, and Z = 4. The strongest lines of the powder X-ray diffraction pattern [d, Å (I, %) (hkl)] are 5.80 (40) (111), 4.50 (20) (201, 210), 4.11 (30) (211), 3.17 (100) (310, 301), 3.02 (20) (311), 2.68 (50) (312, 321), 1.86 (18) (502, 432), 1.62 (18) (523, 532, 611).

Manaevite-(Ce), a new vesuvianite-group mineral has been investigated by means of electron microprobe, TGA and DSC and CHN analysis of H2O, powder X-ray diffraction, single-crystal X-ray structure analysis, 139La NMR, 57Fe Mossbauer spectroscopy, IR spectroscopy and optical measurements. Tetragonal unit-cell parameters are a = 15.9247(13) A, c = 11.9661(10) A, space group P4/nnc. The structure model was solved and refined to R1 = 3.35% for 1757 independent observed reflections with I > 4σ(I). Manaevite-(Ce) is the first vesuvianite-group mineral with the species-defining role of REE3+ at the X3 site. The mineral contains two different kinds of hydroxyl anions. The first type of hydroxyl groups is associated with the O10 and O11 sites as observed for other vesuvianite-group members. Another type of OH groups is due to the hydrogarnet substitution (H4O4)4‒ ↔ (SiO4) 4‒ associated with the Z1 and Z2 sites. The incorporation of REE3+ into the crystal structure of manaevite-(Ce) proceeds via the substitution schemes 2Ca2+ ↔ Th4+ + □ and 3Ca2+ ↔ 2REE3+ + □, which results in the formation of vacancies at the X3 site and the presence of H2O molecules.

The hyalotekite group has been approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (memorandum 57–SM/16). The general formula of the minerals of the hyalotekite group may be written as: A2B2M2[Si8T4O28]W where A = Ba2+, Pb2+ or K+; B = Ba2+, Pb2+ or K+; M = Ca2+, Y3+ or REE3+; T = Si4+, B3+ or Be2+; and W = F– or □ (where REE = rare-earth elements and □ = vacancy).Four minerals are currently known in this group: hyalotekite, Ba4Ca2[Si8B2(SiB)O28]F, triclinic, I$\bar 1$; khvorovite, Pb2+4Ca2[Si8B2(SiB)O28]F, triclinic I$\bar 1$; kapitsaite-(Y), Ba4(YCa)[Si8B2B2O28]F, triclinic, I$\bar 1$; and itsiite Ba4Ca2[Si8B4O28]□, tetragonal, I$\bar 4$2m.We explore the possible end-member compositions within this group by conflating the properties of an end-member with the stoichiometry imposed by the bond topology of the hyalotekite structure-type and the crystal-chemical properties of its known constituents. There are two high-coordination sites in the hyalotekite structure, A and B, and occupancy of each of these sites can be determined only by crystal-structure refinement. If these two sites are considered together, there are 19 end-member compositions of the triclinic structure and six end-member compositions of the tetragonal structure involving A and B = Ba2+, Pb2+, K+; M = Ca2+, Y3+, REE3+; and T = Si4+, B3+, Be2+. There is the possibility for many other hyalotekite-group minerals, and two potential new minerals have been identified from data in the literature.

Mendeleevite-(Nd), (Cs,□)6(□,Cs)6(□,K)6(REE,Ca)30(Si70O175)(OH,H2O,F)35 is a new mineral from the Darai-Pioz alkaline massif, Tajikistan. Mendeleevite-(Nd) was found in a pectolite aggregate in silexites (quartz-rich rocks) which consist of fine to medium pectolite grains, quartz, aegirine and fluorite, with minor khvorovite, mendeleevite-(Ce), sokolovaite, hyalotekite, orlovite, kirchhoffite, pekovite, neptunite, zeravshanite, senkevichite, nordite-(Nd), alamosite, pyrochlore-group minerals and baratovite. Mendeleevite-(Nd) forms colourless cubic crystals 10–40 μm in size; it has a vitreous lustre and a Mohs hardness of 5–5.5; Dmeas. = 3.20(2) g/cm3, Dcalc. = 3.155 g/cm3. Mendeleevite-(Nd) is optically isotropic, with the refractive index n = 1.582(2). Mendeleevite-(Nd) is cubic, space group Pm3̄, a = 21.9106(4) Å; Z = 2. The six strongest reflections in the powder X-ray diffraction pattern are [d (Å), I (%), (h k l)] are: 11.01, 100, (0 0 2); 15.63, 55, (0 1 1); 3.47, 42, (2 0 6); 3.099, 42, (3 4 5); 2.192, 42, (0 0 10); 1.819, 41, (3 6 10). Chemical analysis by electron microprobe gave SiO2 42.30, Ce2O3 10.12, La2O3 3.60, Nd2O3 16.19, Pr2O3 2.79, Sm2O3 4.19, Gd2O3 1.69, Eu2O3 0.47, SrO 2.99, CaO 2.20, Cs2O 8.50, K2O 0.85, H2O 3.85, F 1.25, –O = F2 –0.53, sum 100.46 wt.%, with H2O calculated by analogy with mendeleevite-(Ce). The empirical formula based on 210 (O + F) apfu, with F + OH + H2O = 35 pfu, is Cs6(□4.20K1.80)∑6{[(Nd9.57Ce6.13Sm2.39La2.20Pr1.68Gd0.93Eu0.27)∑23.17(Ca3.90Sr2.87)∑6.77]∑29.94□0.06}∑30(Si70.03O175)(OH14.47F6.54)∑21.01 (H2O)14, Z = 2. The simplified and ideal formulae are (Cs,□)6 (□,Cs)6(□,K)6 (REE,Ca)30 (Si70O175)(OH, H2O,F)35 and Cs6(REE23Ca7)(Si70O175)(OH,F)19(H2O)16, respectively. The compatibility index (from measured density) = – 0.039 (excellent). Mendeleevite-(Nd) is a Nd analogue of mendeleevite-(Ce), (Cs,□)6(□,Cs)6(□,K)6(REE,Ca,□)30(Si70O175)(H2O,OH,F,□)35. Both minerals are named after Dmitri Mendeleev (1834–1907), the great Russian chemist, author of the periodic table of chemical elements, who has had a significant impact on the development of natural sciences and industry, both in Russia and around the world.

Odigitriaite, a new Cs, Na, Ca borosilicate mineral, was discovered in moraine adjacent to the Darai-Pioz alkaline massif in the upper reaches of the Darai-Pioz river at the intersection of the Turkestansky, Zeravshansky and Alaisky mountain ridges, Tajikistan. It occurs as irregular thin flakes associated with quartz, pectolite, baratovite, fluorite, pekovite, polylithionite, aegirine, leucosphenite, pyrochlore, neptunite, reedmergnerite, mendeleevite-(Ce), zeravshanite and sokolovaite. It is colourless with a white streak, is translucent and has a vitreous lustre; it does not fluoresce under ultraviolet light. Odigitriaite is brittle with an uneven fracture and a Mohs hardness of 5. The calculated density is 2.80(2) g/cm3. The indices of refraction are α = 1.502, β = 1.564, γ = 1.576; 2Vobs = 46(2)°, dispersion is weak r > v, and there is no pleochroism. The chemical composition is as follows (electron microprobe, H2O calculated from structure): SiO2 55.30, Al2O3 0.09, Y2O3 0.44, MnO 0.94, FeO 0.10, PbO 0.21, K2O 0.01 Cs2O 8.36, B2O3 4.75, H2O 0.37, F 1.74, O = F2 –0.74, total 99.43 wt.%. The empirical formula of odigitriaite is Cs0.90Na5.12Ca4.68Mn0.20Y0.06Fe0.02Pb0.01[Si13.92Al0.03B2.06O38]F1.39(OH)0.62. The end-member formula is CsNa5Ca5[Si14B2O38]F2. The strong reflections in the powder X-ray diffraction pattern are: [(d, Å), (I, %), (hkl)]: 5.45 (25) (1 1 3), 4.66 (33) (3 1 1), 4.40 (26) (0 2 2), 4.10 (36) (3 1 3), 3.95 (25) (3̄ 1 3), 2.85 (31) (2 2 2), 2.68 (40) (0 0 6), 3.62 (45) (0 2 4), 3.35 (100) (2̄ 2 4), 3.31 (30) (3̄ 1 5), 3.25 (35) (4 0 4), 3.04 (60) (4̄ 2 2), 2.925 (22) (4̄ 2 3), 1.813 (23) (9 1 0). Odigitriaite is monoclinic, space group C2/c, a = 16.652(5), b = 9.598 (3), c = 22.120(7) Å, β= 92.875(14)°, V = 3530.9(1.9) Å3, Z = 4. The crystal structure of odigitriaite was solved by direct methods and refined to an R1 value of 2.75% based on single-crystal X-ray data. It is a double-layer sheet-borosilicate mineral; Cs and Na are intercalated within the double-layer sheet, and the double layers are linked by interstitial Ca and Na atoms.

Wernerbaurite (IMA 2012–064) and schindlerite (IMA 2012–063) from the St. Jude mine, Slick Rock district, San Miguel County, Colorado, USA, were described as hydronium-bearing decavanadate minerals with the formulae {[Ca(H 2 O) 7 ] 2 (H 2 O) 2 (H 3 O) 2 }{V 10 O 28 } and {[Na 2 (H 2 O) 10 ](H 3 O) 4 }{V 10 O 28 }, respectively. Because these phases correspond to known synthetic phases with these formulae, the presence of NH 4 in these minerals was not considered. Recent investigations of a similar phase discovered at a vanadium locality in the Fergana Valley of Kyrgyzstan showed it to contain NH 4 , leading us to reanalyze the original electron-microprobe mounts of wernerbaurite and schindlerite, specifically seeking N; those analyses confirmed the presence of sufficient NH 4 to replace the originally assigned H 3 O. With the additional H sites included and O replaced by N at the NH 4 sites, the structure refinement residual improved for wernerbaurite from R 1 = 3.41% to R 1 = 3.26% and for schindlerite from R 1 = 3.99% to R 1 = 3.70%. The newly assigned NH 4 sites exhibited normal NH 4 –O bond distances and coordination and reasonable bond-valence sums. The H 3 O synthetic equivalents of both phases had been reported, as well as the NH 4 synthetic equivalent of schindlerite. Subsequent to the publication of the original description of the minerals, the NH 4 equivalent of wernerbaurite has also been reported.

Bulgakite, ideally Li 2 (Ca,Na)Fe 2+ 7 Ti 2 (Si 4 O 12 ) 2 O 2 (OH) 4 (O,F)(H 2 O) 2 , and nalivkinite, ideally Li 2 NaFe 2+ 7 Ti 2 (Si 4 O 12 ) 2 O 2 (OH) 4 F(H 2 O) 2 , are astrophyllite-supergroup minerals. Bulgakite is a new mineral from the Darai-Pioz alkaline massif in the upper reaches of the Darai-Pioz river, in the area of the joint Turkestansky, Zeravshansky, and Alaisky ridges, Tajikistan. Bulgakite was found in fenitized amphibole–quartz–feldspar rock with brannockite, sogdianite, bafertisite, albite, and titanite. Bulgakite is brownish orange, transparent in thin grains, and has a vitreous luster. Mohs hardness is 3, D meas. = 3.30(2) g/cm 3 , D calc. = 3.326 g/cm 3 . Bulgakite is biaxial (+) with refractive indices (λ = 589 nm) α = 1.695(3), β = 1.711(2), γ = 1.750(3); 2 V meas. = 70(5)°, 2 V calc. = 67°, strong dispersion: r > v . Cleavage is perfect parallel to {001} and moderate parallel to {010}. Chemical analysis by electron microprobe gave SiO 2 35.63, Al 2 O 3 0.95, Na 2 O 1.04, K 2 O 3.27, Cs 2 O 0.31, CaO 2.56, MgO 0.16, ZnO 0.15, FeO 29.24, MnO 7.14, TiO 2 11.07, Nb 2 O 5 0.49, ZrO 2 0.37, SnO 2 1.18, F 1.01, Li 2 O 1.36 (AAS), Rb 2 O 0.85 (AAS), (H 2 O) calc. 4.04, sum 100.38 wt.%, H 2 O was calculated from crystal-structure analysis. The empirical formula based on 31.94 (O + OH + F + H 2 O) pfu is (Li 0.94 K 0.91 Rb 0.12 Cs 0.03 ) Σ2 (Ca 0.60 Na 0.40 ) Σ1 (Fe 2+ 5.34 Mn 1.32 Li 0.25 Mg 0.05 Na 0.04 Zn 0.02 ) Σ7.02 (Ti 1.82 Sn 0.10 Nb 0.05 Zr 0.04 ) Σ2.01 [(Si 7.78 Al 0.24 ) Σ8.02 O 24 ]O 2 (OH) 4 (F 0.70 O 0.30 )[(H 2 O) 0.94 □ 1.06 ] Σ2 , Z = 1. Bulgakite is triclinic, space group P , a 5.374(1), b 11.965(2), c 11.65(3) A, α 113.457(8), β 94.533(8), γ 103.08(1)°, V 657.5(8) A 3 . The six strongest reflections in the X-ray powder diffraction data [ d (A), I, ( hkl )] are: 10.54, 100, (001); 3.50, 100, (003); 2.578, 100, (130); 2.783, 90, (1 2); 1.576, 68, (3 1, 2); 2.647, 55, ( 11). The crystal structure has been refined to R 1 = 2.6% for 3592 unique F o > 4σ F ) reflections. In the crystal structure of bulgakite, there are four [4] T sites, with T –O> = 1.626 A, occupied mainly by Si, with minor Al. The TO 4 tetrahedra constitute the T 4 O 12 astrophyllite ribbon. The [6] D site is occupied mainly by Ti, with D –φ> = 1.965 A (φ = O, F). The T 4 O 12 astrophyllite ribbons and D octahedra constitute the H (Heteropolyhedral) sheet. In the O (Octahedral) sheet, there are four Fe 2+ -dominant [6] M (1–4) sites, with = 2.159 A (φ = O, OH). Two H and the central O sheets form the HOH block, and adjacent HOH blocks link via a common anion (X P D ) of two D octahedra. In the I (Intermediate) block between adjacent HOH blocks, there are two interstitial cation sites, A and B , and a W site, partly occupied by H 2 O. The A site splits into two partly occupied sites, [13] A (1) and [6] A (2), with A(1)–A(2) = 1.16 A. The [6] A (2) site is occupied by Li with = 2.285 A (φ = O, F, H 2 O), and the [13] A (1) site is occupied by K, Rb, and Cs with = 3.298 A. The aggregate content of the A site is (Li 0.94 K 0.91 Rb 0.12 Cs 0.03 ) Σ2 , ideally Li 2 apfu . The [10] B site is occupied by (Ca 0.60 Na 0.40 ) with B –φ> = 2.593 A. The W site is occupied by [(H 2 O) 0.94 □ 1.06 ] Σ2 pfu . The mineral is named bulgakite after Lev Vasil9evich Bulgak (born 1955), Russian mineralogist, gemologist, and discoverer of several new minerals. The crystal structure of nalivkinite has been revised and refined to R 1 = 4.52% for 3546 unique ( F o > 4σ F ) reflections: space group P , a 5.374(3), b 11.948(5), c 11.676(5) A, α 113.360(6), β 94.538(8), γ 103.01(1)°, V 658.7(9) A 3 , Z = 1, D calc. = 3.347 g/cm 3 . The revised empirical formula of nalivkinite is based on 32.14 (O + OH + F + H 2 O) pfu : (Li 1.14 K 0.75 Cs 0.09 Pb 0.02 ) Σ2 (Na 0.71 Ca 0.29 ) Σ1 (Fe 2+ 5.62 Mn 0.90 Zr 0.08 Na 0.08 Mg 0.04 Zn 0.04 ) Σ6.76 (Ti 1.56 Nb 0.24 Sn 0.09 Zr 0.08 Ta 0.04 ) Σ2 [(Si 7.86 Al 0.15 ) Σ8.01 O 24 ]O 2 (OH) 4 F[(H 2 O) 1.14 □ 0.86 ] Σ2 . The presence of H 2 O groups in the bulgakite and nalivkinite structures was confirmed by infrared spectroscopy. Bulgakite is a Ca-analogue of nalivkinite. Bulgakite and nalivkinite are related by the following substitution: 0.3 B Ca 2+ + 0.3 X O 2– ↔ 0.3 B Na + + 0.3 X F – .

Khvorovite, ideally Pb42+Ca2[Si8B2(SiB)O28]F, is a new borosilicate mineral of the hyalotekite group from the Darai-Pioz alkaline massif in the upper reaches of the Darai-Pioz river, Tajikistan. Khvorovite was found in a pectolite aggregate in silexites (quartz-rich rocks). The pectolite aggregate consists mainly of pectolite, quartz and fluorite, with minor aegirine, polylithionite, turkestanite and baratovite; accessory minerals are calcite, pyrochlore-group minerals, reedmergnerite, stillwellite-(Ce), pekovite, zeravshanite, senkevichite, sokolovaite, mendeleevite-(Ce), alamosite, orlovite, leucosphenite and several unknown Cs-silicates. Khvorovite occurs as irregular grains, rarely with square or rectangular sections up to 150 μm, and grain aggregates up to 0.5 mm. Khvorovite is colourless, rarely white, transparent with a white streak, has a vitreous lustre and does not fluoresce under ultraviolet light. Cleavage and parting were not observed. Mohs hardness is 5–5.5, and khvorovite is brittle with an uneven fracture. The measured and calculated densities are 3.96(2) and 3.968 g/cm3, respectively. Khvorovite is biaxial (+) with refractive indices (λ = 589 nm) α = 1.659(3), βcalc. = 1.671(2), γ = 1.676(3); 2Vmeas. = 64(3)°, medium dispersion: r < v. Khvorovite is triclinic, space group I1¯, a = 11.354(2), b = 10.960(2), c = 10.271(2) Å, α = 90.32(3), β = 90.00(3), γ = 90.00(3)°, V = 1278(1) Å3, Z = 2. The six strongest lines in the powder X-ray diffraction pattern [d (Å), I, (hkl)] are: 7.86, 100, (110); 7.65, 90, (101); 7.55, 90, (011); 3.81, 90, (202); 3.55, 90, (301); 2.934, 90, (312, 312). Chemical analysis by electron microprobe gave SiO2 36.98, B2O3 6.01, Y2O3 0.26, PbO 40.08, BaO 6.18, SrO 0.43, CaO 6.77, K2O 1.72, Na2O 0.41, F 0.88, O=F –0.37, sum 99.35 wt.%. The empirical formula based on 29 (O+F) a.p.f.u. is (Pb2.762+Ba0.62K0.56Na0.16)Σ4.10(Ca1.86Sr0.06Y0.04Na0.04)Σ2[Si8B2(Si1.46B0.65)Σ2.11O28](F0.71O0.29), Z = 2 , and the simplified formula is (Pb2+, Ba, K)4Ca2[Si8B2(Si,B)2O28]F. The crystal structure of khvorovite was refined to R1 = 2.89% based on 3680 observed reflections collected on a four-circle diffractometer with MoKα radiation. In the crystal structure of khvorovite, there are four [4]-coordinated Si sites occupied solely by Si with = 1.617 Å. The [4]-coordinated B site is occupied solely by B, with = 1.478 Å. The [4]-coordinated T site is occupied by Si and B (Si1.46B0.54), with = 1.605 Å; it ideally gives (SiB) a.p.f.u. The Si, B and T tetrahedra form an interrupted framework of ideal composition [Si8B2(SiB)O28]11–. The interstitial cations are Pb2+, Ba and K (minor Na) [A(11–22) sites] and Ca [M site]. The two A sites are each split into two subsites ∼0.5 Å apart and occupied by Pb2+ and Ba + K. The [8]-coordinated M site is occupied mainly by Ca, with minor Sr, Y and Na. Khvorovite is a Pb2+ analogue of hyalotekite, (Ba,Pb2+,K)4(Ca,Y)2[Si8(B,Be)2(Si,B)2O28]F and a Pb2+-, Ca-analogue of kapitsaite-(Y), (Ba,K)4(Y,Ca)2[Si8B2(B,Si)2O28]F. It is named after Pavel V. Khvorov (b. 1965), a Russian mineralogist, to honour his contribution to the study of the mineralogy of the Darai-Pioz massif.

Yusupovite, ideally Na 2 Zr(Si 6 O 15 )(H 2 O) 3 , is a new silicate mineral from the Darai-Pioz alkaline massif in the upper reaches of the Darai-Pioz river, area of the joint Turkestansky, Zeravshansky, and Alaisky ridges, Tajikistan. Yusupovite was found in a pegmatite composed mainly of reedmergnerite, aegirine, microcline, and polylithionite. It occurs as prismatic grains about 2 mm in size embedded in reedmergnerite; associated minerals are quartz, pectolite, zeravshanite, mendeleevite-(Ce), fluorite, leucosphenite, a pyrochlore-group mineral, neptunite, telyushenkoite, moskvinite-(Y), and shibkovite. Yusupovite is colorless, transparent with a white streak, has a vitreous luster, and does not fluoresce under ultraviolet light. Cleavage is perfect on {110}, parting was not observed. Mohs hardness is 5. Yusupovite is brittle with a splintery fracture. The measured and calculated densities are 2.69(2) and 2.713 g/cm 3 , respectively. Yusupovite is optically biaxial (+) with refractive indices (λ = 589 nm) α = 1.563(2), β = 1.565(2), γ = 1.577(2); 2 V meas = 42(3)°, 2 V calc = 45°, strong dispersion: r > v. Yusupovite is monoclinic, C 2/ m , a = 14.5975(4), b = 14.1100(4), c = 14.4394(4) A, β = 90.0399(4)°, V = 2974.1(3) A 3 . The six strongest reflections in the X-ray powder diffraction data [ d (A), I, ( hkl )] are 7.05, 100, (020); 3.24, 96, (420); 3.10, 69, (241, 241); 5.13, 53, (202, 202); 6.51, 42, (201, 201); 3.17, 34, (042). The chemical composition (electron microprobe) is: Nb 2 O 5 0.39, SiO 2 58.84, ZrO 2 16.55, HfO 2 0.30, FeO 0.01, Y 2 O 3 3.05, Cs 2 O 2.58, K 2 O 0.95, Na 2 O 8.91, H 2 O calc 7.40, total 98.98 wt%, with H 2 O calculated from structure refinement. The empirical formula (based on 17.5 O apfu) is (Na 1.76 K 0.12 Cs 0.11 ) ∑1.99 (Zr 0.82 Y 0.17 Nb 0.02 Hf 0.01 ) ∑1.02 (Si 6.01 O 14.98 )(H 2 O) 2.52 , Z = 8. The crystal structure of yusupovite was refined to R 1 = 3.46% based on 4428 observed reflections. In the crystal structure, there are six Si sites occupied by Si, two M sites occupied mainly by Zr with minor Y and Hf. Si tetrahedra form an epididymite Si 6 O 15 ribbon along [010]. Epididymite ribbons and Zr-dominant M octahedra share common vertices to form a heteropolyhedral Si-Zr-O framework. There are six interstitial sites partly occupied by alkali cations Na, K, and Cs. The three [7]-coordinated Na sites are occupied by Na at 95, 84, and 78%. The three A sites are occupied by K and Cs at 12, 18, and 16%. There are 10 W sites occupied by H 2 O groups at 18–84%. Due to (K,Cs), Na and H 2 O disorder, the symmetry of yusupovite decreases from orthorhombic, space group Pbcm (elpidite), to monoclinic, space group C 2/ m , and the b unit-cell parameter of yusupovite is doubled compared to the corresponding cell parameter in elpidite, b yus = 2 a elp . Yusupovite, ideally Na 2 Zr(Si 6 O 15 )(H 2 O) 3 , is a dimorph of elpidite, Na 2 Zr(Si 6 O 15 )(H 2 O) 3 .

Kirchhoffite, CsBSi 2 O 6 , is a new species of silicate mineral from the Darai-Pioz alkaline massif in the upper reaches of the Darai-Pioz River, in the area of the joint Turkestansky, Zeravshansky and Alaisky ridges, Tajikistan. It occurs as equant grains 10 to 80 μm in diameter, associated with quartz, pectolite, baratovite, polylithionite, aegirine, fluorite, leucosphenite, pyrochlore, neptunite and reedmergnerite. Kirchhoffite is colorless, transparent with a white streak, and a vitreous luster; it does not fluoresce under ultraviolet light. No cleavage or parting was observed. The Mohs hardness is 6 to 6½, and it is brittle with a conchoidal fracture. The measured and calculated densities are 3.62(2) and 3.639 g/cm 3 , respectively. Kirchhoffite is uniaxial (+) with indices of refraction ω = 1.592(2), ɛ = 1.600(2). The mineral is tetragonal, space group I 4 1 / acd , a 13.019(2), c 12.900(3) A, V 2186.3(1) A 3 , Z = 16, a : c = 1 : 0.9909. The six strongest lines in the X-ray powder diffraction pattern are [ d in A( I )( hkl )] are 3.26(100) (040), 3.48(82)(132), 2.770(67)(332, 233), 2.294(41)(044), 2.109(34)(352, 253), 5.32(32)(121). Chemical analysis by electron and ion microprobes gave SiO 2 40.47, B 2 O 3 11.27, K 2 O 0.11, Cs 2 O 48.16, Rb 2 O 0.09, for a sum of 100.10 wt.%. The resulting empirical formula on the basis of six atoms of oxygen is (Cs 1.02 K 0.01 ) ∑1.03 B 0.96 Si 2.02 O 6 , ideally CsBSi 2 O 6 . The crystal structure of kirchhoffite was refined to an R 1 index of 3.1% based on 487 observed reflections collected on a four-circle diffractometer with Mo K α X-radiation. In the structure, there are two tetrahedrally coordinated sites: Si is occupied by silicon, Si –O> = 1.610 A, B is occupied by boron, B –O> = 1.465 A, and Cs is [12]-coordinated, = 3.301 A. Tetrahedra form a [BSi 2 O 6 ] framework, the topology of which is identical to that of tetragonal pollucite, CsAlSi 2 O 6 . The [12]-coordinated Cs atoms occupy the channels along [111] formed by six-membered rings of tetrahedra. Kirchhoffite, CsBSi 2 O 6 , is a B analogue of the tetragonal modification of pollucite.

Two new mineral species, vorontsovite, ideally (Hg5Cu)TlAs4S12, and ferrovorontsovite, ideally (Fe5Cu)TlAs4S12, the Tl- and Tl–Fe-analogues of galkhaite, respectively, have been discovered at the Vorontsovskoe gold deposit, Northern Urals, Russia. They occur as anhedral grains up to 0.5 mm (vorontsovite) and 0.2 mm (ferrovorontsovite) embedded in a calcite-dolomite matrix. The chemical composition of vorontsovite (wt %) is: Hg 35.70, Fe 5.36, Zn 1.26, Cu 3.42, Ag 0.64, Tl 11.53, Cs 0.35, Pb 0.04, As 15.98, Sb 2.35, Te 0.41, S 22.70, Se 0.02, total 99.76. The empirical formula, calculated on the basis of 23 atoms pfu, is: [(Hg3.02Fe1.63Zn0.33)Σ4.98(Cu0.91Ag0.10)Σ1.01](Tl0.96Cs0.04)Σ1.00(As3.62Sb0.33Te0.05)Σ4.00S12.01. The composition of ferrovorontsovite (wt %) is: Hg 25.13, Fe 9.89, Zn 1.16, Cu 3.95, Ag 0.45, Tl 12.93, Cs 0.44, Pb 0.04, As 17.83, Sb 2.15, Te 0.40, S 24.91, total 99.28. The empirical formula, calculated on the basis of 23 atoms pfu, is: [(Fe2.74Hg1.94Zn0.27)Σ4.95(Cu0.96Ag0.06)Σ1.02](Tl0.98Cs0.05)Σ1.03(As3.68Sb0.27Te0.05)Σ4.00S12.00. Both minerals are cubic, space group I-43m, with a = 10.2956(6) Å, V = 1091.3(1) Å3, Z = 2 (vorontsovite); and a = 10.2390(7) Å, V = 1073.43(22) Å3, Z = 2 (ferrovorontsovite). The crystal structures of both minerals were refined to R = 0.0376 (vorontsovite) and R = 0.0576 (ferrovorontsovite). Vorontsovite and ferrovorontsovite have been approved by the IMA-CNMNC under the numbers 2016-076 and 2017-007, respectively. The first one is named after the type locality, but also honors the mining engineer Vladimir Vasilyevich Vorontsov. The second is named for its chemical composition, as the Fe-analogue of the first. Both species are isostructural with galkhaite, being its Tl- and Tl–Fe analogues, respectively, and forming altogether the galkhaite group.

Three old specimens, collected in the 19 th century and now deposited in Fersman Mineralogical Museum, Moscow, are labeled as rhodizite from the Sarapulka, Shaitanka (both cotype localities) and Alabashka granitic pegmatite fields, Central Urals, Russia. All are Cs-dominant (Cs > K) and must now be considered londonite. The crystal structure of londonite from Sarapulka was solved from single-crystal data collected at 193 K and refined to R = 0.0203. The mineral is cubic, space group P 43 m, a 7.3149(7) A. Its structure is based on a microporous quasi-framework formed by clusters of four edge-sharing AlO 6 octahedra linked by BO 4 and BeO 4 tetrahedra. Both Cs + and K + are ordered in the cages of the quasi-framework. The very short Cs–K distance, 0.51(3) A, prevents simultaneous occupancy of these positions in the same cage. The Be and K atoms are also separated by an unallowable short distance of 2.76(3) A, and thus their contents are coupled. The solid-solution system between rhodizite (K-dominant), londonite (Cs-dominant) and the hypothetical K- and Cs-free analogue, (□,H 2 O){Al 4 [Be 4 B 12 O 28 ]}, is complicated, with numerous coupled heterovalent substitutions. Taking into consideration chemical, structural and IR data, it can be presented as: ( A ,□,H 2 O) 1 ( Al ,Li) 4 ( Be ,Li,Al,□ ) 4 ( B ,Be) 12 [ O 28− x (OH,F) x ], where A = K , Cs and x 4 O 4 ] clusters and a sodalite-type [B 12 O 24 ] framework results in the formation of an original complex, [Al 4 O 4 B 12 O 24 ], in rhodizite and londonite.

Nous avons affine la structure cristalline de la senkevichite, de composition ideale Cs K Na Ca 2 T1 4+ O [Si 7 O 18 (OH)], triclinique, PI, a 10.4191(4), b 12.2408(5), c 7.0569(3) A, a 90.857(1), β 99.193(1). γ 91.895(1)°, V 887.8(1) A 3 , Z= 2. D calc 3.125 g/cm 3 , provenant du complexe de Dara-i-Pioz, dans les montagnes Tien-Shan. au Tajikistan, jusqu'a un residu R 1 de 4.5% en utilisant 4872 reflexions uniques (F o > 4σF) prelevees avec un diffractometre a monocristal Bruker P4 muni d'un detecteur CCD 4K et rayonnement MoKα. Les analyses effectuees avec une microsonde electronique ont donne SiO 2 51.08 TiO 2 8.94, FeO 0.50, MnO 2.59, CaO 10.98, K 2 O 6.13, Na 2 O 3.76, Nb 2 O 5 0.64, Cs 2 O 15.28, (H 2 O) calc 1.09, pour un total de 100.99% (poids), et la proportion de (H 2 O) a ete etablie par analyse de la structure. La senkevichite est isostructurale avec la tinaksite et la tokkoite. La structure contient sept sites Si a coordinence tetraedrique, avec une distance moyenne de 1.623 A. Six de ces sites sont coordonnes par des atomes d'oxygene, et le site Si(7) est coordonne par trois atomes d'oxygene et un groupe (OH). Il s'agit donc d'un groupe silicate acide. Il y a trois sites M a coordinence [6]. Le site M(1) contient surtout T1 4+ (et un peu de Nb), avec = 1.985 A. Le site M(2) contient uniquement Ca, avec = 2.382 A, et le site M(3) contient Ca (et des quantites mineures de Fe 2+ et Mn 2+ ). avec = 2.317 A. Il y a un site Na a coordinence [7], avec = 2.504 A. Il y a deux sites A, le site A(1) a coordinence [12], contenant surtout le cesium (et un peu de K), avec = 3.318 A. et le site A(2), a coordinence [10], contenant uniquement le K, avec = 2.987A. La senkevichite est l'analoque a Cs de la tinaksite, K 2 Na Ca 2 T1 4+ O [S1 7 O 18 (OH)], et l'oxyanalogue a Cs-Na-Ti 4+ de la tokkoite, K 2 Ca 4 F |Si 7 O 18 (OH)].