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The crystal structure and chemical formula of zvyaginite, ideally Na2ZnTiNb2(Si2O7)2O2(OH)2(H2O)4, a lamprophyllite-group mineral of the seidozerite supergroup from the type locality, Mt. Malyi Punkaruaiv, Lovozero alkaline massif, Kola Peninsula, Russia have been revised. The crystal structurewas refined with a new origin in space group C1, a = 10.769(2), b = 14.276(3), c = 12.101(2) Å, α = 105.45(3), β = 95.17(3), γ = 90.04(3)°, V = 1785.3(3.2) ų, R1 = 9.23%. The electron-microprobe analysis gave the following empirical formula [calculated on 22 (O + F)]: (Na0.75Ca0.09K0.04□1.12)Σ2 (Na1.12Zn0.88Mn0.17Fe0.042+□0.79)Σ3 (Nb1.68Ti1.25Al0.07)Σ3 (Si4.03O14)O2 [(OH)1.11F0.89]Σ2(H2O)4, Z = 4. Electron-diffraction patterns have prominent streaking along c* and HRTEM images show an intergrowth of crystalline zvyaginite with two distinct phases, both of which are partially amorphous. The crystal structure of zvyaginite is an array of TS (Titanium-Silicate) blocks connected via hydrogen bonds between H2O groups. The TS block consists of HOH sheets (H = heteropolyhedral, O = octahedral) parallel to (001). In the O sheet, the [6]MO(1,4,5) sites are occupied mainly by Ti, Zn and Na and the [6]MO(2,3) sites are occupied by Na at less than 50%. In the H sheet, the [6]MH(1,2) sites are occupied mainly by Nb and the [8]AP(1) and [8]AP(2) sites are occupied mainly by Na and □. The MH and AP polyhedra and Si2O7 groups constitute the H sheet. The ideal structural formula is Na□Nb2NaZn□Ti(Si2O7)2O2(OH)2(H2O)4. Zvyaginite is a Zn-bearing and Na-poor analogue of epistolite, ideally (Na□)Nb2Na3Ti(Si2O7)2O2(OH)2(H2O)4. Epistolite and zvyaginite are related by the following substitution in the O sheet of the TS-block: (Na2+)epi↔Znzvy2+ +□zvy. The doubling of the t1 and t2 translations of zvyaginite relative to those of epistolite is due to the order of Zn and Na along a (t1) and b (t2) in the O sheet of zvyaginite. [ABSTRACT FROM AUTHOR]

Fogoite-(Y), Na3Ca2Y2Ti(Si2O7)2OF3, is a new mineral from the Lagoa do Fogo, SãoMiguel Island, theAzores. It occurs in cavities as highly elongated (on [001]) prisms, up to 2000 μm long and 50 μm × 50 μm in crosssection, associated with sanidine, astrophyllite, fluornatropyrochlore, ferrokentbrooksite, quartz and ferrokatophorite. Crystals are generally transparent and colourless, with vitreous lustre, occasionally creamy white. Fogoite-(Y) has a white streak, splintery fracture and very good {100} cleavage. Mohs hardness is ~5. Dcalc. = 3.523 g/cm3. It is biaxial (+) with refractive indices (λ = 590 nm) α = 1.686(2), β = 1.690(2), γ = 1.702(5); 2Vmeas.= 57(1)° and 2Vcalc. = 60°. It is nonpleochroic. Fogoite-(Y) is triclinic, space group P1̄, a = 9.575(6), b = 5.685(4), c = 7.279(5) Å, α = 89.985(6), β = 100.933(4), γ = 101.300(5)°, V = 381.2 (7)Å3. The six strongest reflections in the powder X-ray diffraction data [d (Å), I, (h k l)] are: 2.954, 100, (1̄ 1̄ 2, 3̅ 1 0); 3.069, 42, (3 0 0, 0 1̄ 2); 2.486, 24, (3 1 0, 2 1̄ 2); 3.960, 23, (1̄ 1̄ 1, 2̄̅ 1 0); 2.626, 21, (2̄̅ 2 0); 1.820, 20, (1̄ 0 4). Electron microprobe analysis gave the following empirical formula calculated on 18 (O + F) (Na2.74Mn0.15)Σ2.89Ca2[Y1.21(La0.01Ce0.03 Nd0.03Sm0.02Gd0.08Dy0.08Er0.05Yb0.04Lu0.01)Σ0.35Mn0.16 Zr0.11Na0.09 Fe2+0.07Ca0.01]Σ2(Ti0.76Nb0.23Ta0.01)Σ1(Si4.03O14)O1.12F2.88, Z = 1. The crystal structure was refined on a twinned crystal to R1 = 2.81% on the basis of 2157 unique reflections (Fo > 4σFo) and is a framework of TS (Titanium Silicate) blocks, which consist of HOH sheets (H - heteropolyhedral, O - octahedral) parallel to (100). In the O sheet, the the [6]MO(1) site is occupied mainly by Ti, = 1.623 Å; the [6]MH site is occupied by Yand rare-earth elements (Y > REE), with minor Mn, Zr, Na, Fe2+ and Ca, = 2.271 Å and the [6]AP site is occupied by Ca, = 2.416 Å. The MH and AP octahedra and Si2O7 groups constitute the H sheet. The ideal compositions of the O and two H sheets are Na3Ti(OF)F2 and Y2Ca2(Si2O7)2 apfu. Fogoite-(Y) is isostructural with götzenite and hainite. The mineral is named after the type locality, the Fogo volcano in the Azores. [ABSTRACT FROM AUTHOR]

The crystal structure of hejtmanite, Ba2Mn4Ti2(Si2O7)2O2(OH)2F2, from Mbolve Hill, Mkushi River area, Central Province, Zambia (holotype material) has been refined on a twinned crystal to R1 = 1.88% on the basis of 4539 [|F| > 4σ|F|] reflections. Hejtmanite is triclinic, C, a = 10.716(2), b = 13.795(3), c = 11.778(2) Å, α = 90.07(3), β = 112.24(3), γ = 90.03(3)°, V = 1612(2) ų. Chemical analysis (electron microprobe) gives: Ta2O5 0.09, Nb2O5 1.27, ZrO2 0.65, TiO2 14.35, SiO2 23.13, BaO 26.68, SrO 0.19, FeO 11.28, MnO 15.12, Cs2O 0.05, K2O 0.33, F 3.82, H2Ocalc. 1.63, O = F -1.61, total 97.10 wt.%, where the H2O content was calculated from the crystal-structure refinement, with (OH + F) = 4 apfu. The empirical formula, calculated on the basis of 20 (O + F) anions, is of the form (Si2O7)2(XO)4(XP)2, Z = 4: (Ba1.82K0.07Sr0.02)Σ1.91(Mn2.33 Zr0.04Mg0.03)Σ3.95(Ti1.88Nb0.10Zr0.02)Σ2(Si2.02O7)2O2[(OH)1.89 F0.11]Σ2F2. The crystal structure is a combination of a TS (Titanium Silicate) block and an I (intermediate) block. The TS block consists of HOH sheets (H - heteropolyhedral, O - octahedral). The topology of the TS block is as in Group-II TS-block minerals: Ti (+ Nb) = 2 apfu per (Si2O7)2 [as defined by Sokolova (2006)]. In the O sheet, five [6]MO sites are occupied mainly by Mn, less Fe2+ and minor Zr and Mg, with < MO-φ> = 2.198 Å (φ = O,OH), ideally giving Mn4 apfu. In the H sheet, two [6]MH sites are occupied mainly by Ti, with < MH-φ> = 1.962 Å (φ = O,F), ideally giving Ti2 apfu; four [4]Si sites are occupied by Si, with < Si-O> = 1.625 Å. The MH octahedra and Si2O7 groups constitute the H sheet. The two [12]Ba-dominant AP(1,2) sites, with  = 2.984 Å (φ = O, F), ideally give Ba2 apfu. Two (1,2) and two (1,2) sites are occupied by O atoms and OH groups with minor F, respectively, ideally giving (XO)4 = (XMO)2 + (XAO)2 = O2(OH)2 pfu. Two (1,2) sites are occupied by F, giving F2 apfu. TS blocks link via a layer of Ba atoms which constitute the I block. Simplified and end-member formulae of hejtmanite are Ba2(Mn,Fe2+)4Ti2 (Si2O7)2O2(OH,F)2 F2 and Ba2Mn4Ti2(Si2O7)2O2(OH)2F2, Z = 4. Hejtmanite is a Mn-analogue of bafertisite, Ba2 Ti2(Si2O7)2O2(OH)2F2. [ABSTRACT FROM AUTHOR]

Berezanskite, ideally Ti2□2KLi3(Si12O30), is hexagonal, space group P6/mcc, a=9.898(4), c=14.276(6) Å, V=1211.2(9) ų, Z=2. The crystal structure was refined to an R1 index of 2.08% based on 392 unique observed reflections. Berezanskite is isostructural with milarite, ideally ACa2BoCKT(2)(Be2Al)(T(1)Si12O30)(H2O)0-2. The structural unit is of the form [T(2)3T(1)12O30] with T(1)=Si and T(2)=Li, in which (LiO4) tetrahedra link [Si12O30] six-membered double-rings into a framework. The A, B and C sites occur in the interstices of the framework with the following site populations: A=Ti4+2, =1.938(2) Å; B=□2; C=K, =3.058(2) Å. In the T(2)=Li3 milarite-group minerals, the distance is inversely related to the occupancy of the B site. [ABSTRACT FROM AUTHOR]

Bobshannonite, Na2KBa(Mn,Na)8(Nb,Ti)4(Si2O7)4O4(OH)4(O,F)2, is a new TS-block mineral from Mont Saint-Hilaire, Québec, Canada. It occurs as blocky crystals 0.5−1 mm across, perched on sérandite and albite. Other associated minerals are epididymite, catapleiite, aegirine, kupletskite, rhodochrosite and rhabdophane-(Ce). Bobshannonite occurs as vitreous to frosty, transparent to translucent very pale brown to orange brown crystals, has a very pale brown streak, hackly fracture and does not fluoresce under cathode or ultraviolet light. Cleavage is {001} very good, no parting was observed, Mohs hardness is ~4, it is brittle and Dcalc. = 3.787 g/cm3. Crystals are twinned extensively and do not extinguish in cross-polarized light. Bobshannonite is triclinic, C1̄, a = 10.839(6), b = 13.912(8), c = 20.98(1) Å, α = 89.99(1), β = 95.05(2), γ = 89.998(9)°, V = 3152(5) Å3. The six strongest reflections in the powder X-ray diffraction data [d (Å), I, (hkl)] are: 2.873, 100, (2̅4̅1, 2̅41, 044, 04̅4, 241, 24̅1); 3.477, 60, (006); 3.193, 59, (224, 22̅4); 2.648, 40, (4̅02, 243, 24̅3); 2.608, 35, (008, 226, 22̅6); 1.776, 30, (249). Chemical analysis by electron microprobe gave Ta2O5 0.52, Nb2O5 19.69, TiO2 5.50, SiO2 26.31, Al2O3 0.06, BaO 7.92, ZnO 1.02, FeO 0.89, MnO 26.34, MgO 0.06, Rb2O 0.42, K2O 2.38, Na2O 4.05, F 0.70, H2Ocalc. 1.96, O = -0.29, total 97.53 wt.%, where the H2O content was calculated from the crystal-structure analysis. The empirical formula on the basis of 38 anions is Na1.89(K0.93Rb0.08)Σ1.01Ba0.95(Mn6.85Na0.52Zn0.23Fe0.232+ Mg0.03Al0.02)Σ7.88 (Nb2.73Ti1.27Ta0.04)Σ4.04(Si8.07O28)O9.32H4.01F0.68, Z = 4. The crystal structure was refined to R1 = 2.55% on the basis of 7277 unique reflections [F > 4σ(F)] and can be described as a combination of a TS (Titanium Silicate) block and an I (Intermediate) block. The TS block consists of HOH sheets (H - heteropolyhedral, O − octahedral). The topology of the TS block is as in Group II of the Ti disilicates: Ti + Nb = 2 a.p.f.u. per (Si2O7)2 [as defined by Sokolova (2006)]. In the O sheet, ten [6]MO sites are occupied mainly by Mn, less Na and minor Zn, Fe2+, Mg and Al, with = 2.223 Å. In the H sheet, four [6]MH sites are occupied by Nb and Ti (Nb > Ti), with = 1.975 Å, and eight [4]Si sites are occupied by Si, with = 1.625 Å. The MH octahedra and Si2O7 groups constitute the H sheet. The TS blocks link via common vertices of MH octahedra. In the I block, Ba and K are ordered at the AP(1) and AP(2) sites with Ba:K = 1:1 and the two BP sites are occupied by Na. The ideal composition of the I block is Na2KBa a.p.f.u. Bobshannonite, perraultite, surkhobite and jinshajiangite are topologically identical Group-II TS-block minerals. Bobshannonite is the Nb-analogue of perraultite. The mineral is named bobshannonite after Dr. Robert (Bob) D. Shannon (b. 1935), in recognition of his major contributions to the field of crystal chemistry in particular and mineralogy in general through his development of accurate and comprehensive ionic radii and his work on dielectric properties of minerals. [ABSTRACT FROM AUTHOR]

Veblenite, ideally K2⧠22Na(Fe2+5Fe3+ 4 Mn2+ 7⧠)Nb3Ti(Si2O7)2(Si8O22)2O6(OH)10(H2O)3, is a new mineral with no natural or synthetic analogues. The mineral occurs at Ten Mile Lake, Seal Lake area, Newfoundland and Labrador (Canada), in a band of paragneiss consisting chiefly of albite and arfvedsonite. Veblenite occurs as red brown single laths and fibres included in feldspar. Associated minerals are niobophyllite, albite, arfvedsonite, aegirine-augite, barylite, eudidymite, neptunite, Mnrich pectolite, pyrochlore, sphalerite and galena. Veblenite has perfect cleavage on {001} and splintery fracture. Its calculated density is 3.046 g cm-3. Veblenite is biaxial negative with α 1.676(2), β 1.688(2), γ 1.692(2) (λ 590 nm), 2Vmeas = 65(1)°, 2Vcalc = 59.6°, with no discernible dispersion. It is pleochroic in the following pattern: X = black, Y = black, Z = orange-brown. The mineral is red-brown with a vitreous, translucent lustre and very pale brown streak. It does not fluoresce under short and long-wave UV-light. Veblenite is triclicnic, space group P1, a 5.3761(3), b 27.5062(11), c 18.6972(9)Å,α 140.301(3), β 93.033(3), γ 95.664(3)°, V = 1720.96(14) Å3. The strongest lines in the X-ray powder diffraction pattern [d(Å )(I)(hkl)] are: 16.894(100)(010), 18.204(23)(011), 4.271(9)(141, 040, 120),11.661(8)(001), 2.721(3)(19-5), 4.404(3)(13 2, 142), 4.056(3)(031, 11-2; 152, 14 3), 3.891(2)(003). The chemical composition of veblenite from a combination of electron microprobe analysis and structural determination for H2O and the Fe2+/Fe3+ ratio is Nb2O5 11.69, TiO2 2.26, SiO2 35.71, Al2O3 0.60, Fe2O3 10.40, FeO 11.58, MnO 12.84, ZnO 0.36, MgO 0.08, BaO 1.31, SrO 0.09, CaO 1.49, Cs2O 0.30, K2O 1.78, Na2O 0.68, H2O 4.39, F 0.22, O = F -0.09, sum 95.69 wt.%. The empirical formula [based on 20 (Al+Si) p.f.u. is (K0.53Ba0.28Sr0.03⧠0.16)Σ1(K0.72Cs0.07⧠1.21)Σ2(Na0.72Ca0.17⧠1.11)Σ2 (Fe2+5.32Fe3+4.13Mn2+5.97Ca0.70Zn0.15Mg0.07⧠0.66)Σ17(Nb2.90Ti0.93Fe3+0.17)Σ4(Si19.61Al0.39)Σ20O77.01 H16.08F0.38. The simplified formula is (K,Ba,⧠)3(⧠,Na)2(Fe2+,Fe3+,Mn2+)17(Nb,Ti)4(Si2O7)2 (Si8O22)2O6(OH)10(H2O)3. The infrared spectrum of the mineral contains the following bands (cm-1): 453, 531, 550, 654 and 958, with shoulders at 1070, 1031 and 908. A broad absorption was observed between ∼3610 and 3300 with a maximum at ∼3525. The crystal structure was solved by direct methods and refined to an R1 index of 9.1%. In veblenite, the main structural unit is an HOH layer, which consists of the octahedral (O) and two heteropolyhedral (H) sheets. The H sheet is composed of Si2O7 groups, veblenite Si8O22 ribbons and Nb-dominant D octahedra. This is the first occurrence of an eight-membered Si8O22 ribbon in a mineral crystal structure. In the O sheet, (Fe2+, Fe3+, Mn2+) octahedra share common edges toform a modulated O sheet parallel to (001). HOH layers connect via common vertices of D octahedra and cations at the interstitial A(1,2) and B sites. In the intermediate space between two adjacent HOH layers, the A(1) site is occupied mainly by K; the A(2) site is partly occupied by K and H2O groups, the B site is partly occupied by Na. The crystal structure of veblenite is related to several HOH structures: jinshanjiangite, niobophyllite (astrophyllite group) and nafertisite. The mineral is named in honour of David R. Veblen in recognition of his outstanding contributions to the fields of mineralogy and crystallography. [ABSTRACT FROM AUTHOR]