Leonid A. Pautov

The crystal structure and crystal chemistry of mendeleevite-(Ce), (Cs,□)6(□,Cs)6(□,K)6(REE,Ca,□)30(Si70O175)(H2O,OH,F,□)35, a potential microporous material

Abstract The crystal structure of mendeleevite-(Ce), (Cs,⃞)6(⃞,Cs)6(⃞,K)6(REE,Ca,⃞)30(Si70O175) (H2O,OH,F,⃞)35, a new mineral from the moraine of the Darai-Pioz glacier, the Alai mountain ridge, Tien-Shan mountains, northern Tajikistan, was solved by direct methods and refined to R1 = 4.15% based on 2274 observed [Fo > 4σ|F|] unique reflections measured with Mo-Kα radiation on a Bruker P4 diffractometer equipped with a CCD detector. Mendeleevite-(Ce) is cubic, space group Pm3̄, a 21.9148(4) Å, V 10525(1) Å3, Z = 2, Dcalc = 3.066 g/cm3. The empirical formula (electron microprobe) is Cs5.94K2 .22[(Ce11.35La5.86Nd3.23Pr1.54Sm0.32Gd0.20)∑22.50(Ca4.68Sr1.00)∑5.68]∑28.18 Si70.12O203.17H45.67F6.83, Z = 2, calculated on the basis of 210 (O + F) a.p.f.u., with H2O and OH calculated from structure refinement (OH + F = 17 p.f.u.; H2O = 17.75 p.f.u.). The structural formula is (Cs4.65⃞1.35)∑6(⃞4.71Cs1.29)∑6(⃞3.78K2.22)∑6{[(Ce11.35La5.86Nd3.23 Pr1.54Sm0.32Gd0.20)∑22.50(Ca4.68Sr1.00)∑5.68]∑28.18⃞1.82}∑30(Si70O175)[(OH)10.17F6.83]∑17(H2O)17.75. Simplified and endmember formulae are as follows: (Cs,⃞)6(⃞,Cs)6(⃞,K)6(REE,Ca,⃞)30(Si70O175)(H2O,OH,F,⃞)35 and Cs6(REE22Ca6)(Si70O175)(OH,F)14(H2O)21. The crystal structure of mendeleevite-(Ce) is an intercalation of two independent Si-O radicals and an M framework of (REE,Ca) polyhedra. The Si-O radicals are an(Si 104O260)104- framework and an (Si36O90)36-cluster which do not link directly. The M framework is located between the Si-O framework and the Si-O clusters. Interstitial cations occupy two types of cages and channels. Cages I and II are 78 and 22% occupied by Cs. Channels along [100⃞] contain K atoms and H2O groups. Mendeleevite-(Ce) has no natural or synthetic structural analogues. Mendeleevite-(Ce) is a framework mineral with large cavities and it has the potential to be used as a model for the synthesis of microporous materials of industrial interest.

From structure topology to chemical composition. XX. Titanium silicates : The crystal structure of hejtmanite, Ba2Mn4Ti2(Si2O7)2O2(OH)2F2, a Group-II TS-block mineral

Abstract 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, C1̄, 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) Å3. 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 AP2MO4MH2(Si2O7)2(XO)4(XP)2, Z=4:(Ba1.82K0.07Sr0.02)Σ1.91(Mn2.33Fe2+1.65Zr0.04Mg0.03)Σ3.95(Ti1.88Nb0.10Zr0.02)Σ2(Si2.02O7)2O2[(OH)1.89F0.11]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 = 2.198 Å(φ = O,OH), ideally giving Mn4 apfu. In the H sheet, two [6]MH sites are occupied mainly by Ti, with = 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 XOM(1,2) and two XOA(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 XPM(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)2F2 and Ba2Mn4Ti2(Si2O7)2O2(OH)2F2, Z = 4. Hejtmanite is a Mn-analogue of bafertisite, Ba2Fe2+4Ti2(Si2O7)2O2(OH)2F2.

Byzantievite, Ba5(Ca,REE,Y)22(Ti,Nb)18(SiO4)4[(PO4),(SiO4)]4 (BO3)9O21[(OH),F]43(H2O)1.5: the crystal structure and crystal chemistry of the only known mineral with the oxyanions (BO3), (SiO4) and (PO4)

Abstract The crystal structure of byzantievite, Ba5(Ca,REE,Y)22(Ti,Nb)18(SiO4)4[(PO4),(SiO4)]4(BO3)9O21 [(OH),F]43(H2O)1.5, a new mineral from the moraine of the Dara-i-Pioz glacier, the Alai mountain ridge, Tien-Shan Mountains, northern Tajikistan, was solved by direct methods and refined to R1 = 13.14% based on 3794 observed [Fo >4σ|F|] unique reflections measured with Mo-Ka X-radiation on a Bruker P4 diffractometer equipped with a CCD detector. Byzantievite is hexagonal, space group R3, a = 9.1202(2) Å, c = 102.145(5) Å, V = 7358.0(5) Å3, Z = 3, Dcalc. = 4.151 g cm−3. The empirical formula (electron microprobe analysis) is Ba5.05[(Ca8.99Sr0.96Fe2+0.42Na0.20)∑10.5(Ce3.46La1.54Nd1.20 Pr0.30Sm0.26Dy0.41Gd0.32Th0.39U4+0.17)∑8.05Y3.53]∑22.15(Ti12.31Nb5.30)∑17.61(SiO4)4.65(PO4)3.12(BO3)8.89 O22.16(OH)38.21F4.89(H2O)1.5, Z = 3, calculated on the basis of 124.5 (O + F) a.p.f.u. The H2O and OH contents were calculated from structure refinement (F + OH = 43 a.p.f.u.; H2O = 1.5 a.p.f.u..), and B was determined by SIMS. The crystal structure is a framework of Ti-Ba-Ca-REE-dominant polyhedra and SiO4, PO4 and BO3 groups. In the crystal structure, there are 50 cation sites, 23 of which are fully occupied and 27 partly occupied: six of the 27 partly-occupied sites are >50% occupied, 21 <50% occupied. The crystal structure of byzantievite is an intercalation of three components, one fully ordered with 100% occupancy of cation sites, and two partly ordered with cation-site occupancies of 67% and 17% respectively. Byzantievite is the only known mineral that contains all three of the oxyanions (BO3), (SiO4) and (PO4) as essential components.

Yusupovite, Na2Zr(Si6O15)(H2O)3, a new mineral species from the Darai-Pioz alkaline massif and its implications as a new microporous filter for large ions

Abstract Yusupovite, ideally Na2Zr(Si6O15)(H2O)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/cm3, respectively. Yusupovite is optically biaxial (+) with refractive indices (λ = 589 nm) α = 1.563(2), β = 1.565(2), γ = 1.577(2); 2Vmeas = 42(3)°, 2Vcalc = 45°, strong dispersion: r > v. Yusupovite is monoclinic, C2/m, a = 14.5975(4), b = 14.1100(4), c = 14.4394(4) Å, β = 90.0399(4)°, V = 2974.1(3) Å3. The six strongest reflections in the X‑ray powder diffraction data [d (Å), I, (hkl)] are 7.05, 100, (020); 3.24, 96, (420); 3.10, 69, (241, 2̅41); 5.13, 53, (202, 2̅02); 6.51, 42, (201, 2̅01); 3.17, 34, (042). The chemical composition (electron microprobe) is: Nb2O5 0.39, SiO2 58.84, ZrO2 16.55, HfO2 0.30, FeO 0.01, Y2O3 3.05, Cs2O 2.58, K2O 0.95, Na2O 8.91, H2Ocalc 7.40, total 98.98 wt%, with H2O calculated from structure refinement. The empirical formula (based on 17.5 O apfu) is (Na1.76K0.12Cs0.11)∑1.99 (Zr0.82Y0.17Nb0.02Hf0.01)∑1.02(Si6.01O14.98)(H2O)2.52, Z = 8. The crystal structure of yusupovite was refined to R1 = 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 Si6O15 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 H2O groups at 18-84%. Due to (K,Cs), Na and H2O disorder, the symmetry of yusupovite decreases from orthorhombic, space group Pbcm (elpidite), to monoclinic, space group C2/m, and the b unit-cell parameter of yusupovite is doubled compared to the corresponding cell parameter in elpidite, byus = 2aelp. Yusupovite, ideally Na2Zr(Si6O15)(H2O)3, is a dimorph of elpidite, Na2Zr(Si6O15)(H2O)3.

The crystal structure of laptevite-(Ce), NaFe2+(REE7Ca5Y3)(SiO4)4(Si3B2PO18)(BO3)F11, a new mineral species from the Darai-Pioz alkaline massif, Northern Tajikistan

Abstract Laptevite-(Ce), ideally NaFe2+(REE7Ca5Y3) · (SiO4)4(Si3B2PO18)(BO3)F11, is a new member of the vicanite group discovered in the moraine of the Darai-Pioz glacier, Alai Mountain Range, Tien-Shan, Tajikistan. The crystal structure of laptevite-(Ce), trigonal, a = 10.804(2) Å , c = 27.726(6) Å , V = 2802.6(2) Å 3, sp. gr. R3m, Z = 3, Dcalc. = 4.660 · 103 kg/m3, has been refined to R1 = 0.0387 for 924 unique (Fo > 4σF) reflections, collected on a Bruker single-crystal P4 diffractometer with a 4K CCD detector and Mo-Ka X-radiation. The simplified formula is NaFe2+(REE,Ca,Y)15(SiO4)4 [(Si,B,P)6O18](BO3)F11. In the crystal structure of laptevite-( Ce), there are four tetrahedrally coordinated T sites. The T(1) site is occupied by Si and minor B, 〈T(1)-O〉 = 1.594 Å ; the T(2, 3) sites are occupied by Si, 〈T(2,3)-O〉 = 1.64 Å ; the T(4) site is occupied by B, P and minor Si, with 〈T(4)-O〉 = 1.51 Å . The [3]-coordinated T(5) site has composition B0.84⃞0.16, with 〈T(5)-O〉 = 1.42 Å . Cations at the T(1 + 4), T(2, 3) and T(5) sites form the complex anions (Si3B2PO18), (SiO4)4 and (BO3), respectively. The [7-10-coordinated M(1-5) sites are occupied by REE, Ca, Y and minor Sr, with 〈M(1-5)-O〉 = 2.37-2.62 Å . The octahedrally coordinated M(6) site is occupied by Fe2+ > Mn > Ti, with 〈M(6)-O〉 =2.13 Å . The [10]-coordinated M(7) site has composition Na0.75REE0.25, with 〈M(7)-O〉 = 2.64 Å . The T and M polyhedra form a framework. Laptevite-(Ce) is isostructural with other vicanite-group minerals: vicanite- (Ce), okanoganite-(Y), hundholmenite-(Y) and proshchenkoite-(Y). Vicanite-group structures differ in the dominant cation species at the T(1, 3-6) and M(3-7) sites.

Mendeleevite-(Nd), (Cs,□)6(□,Cs)6(□,K)6(REE,Ca)30(Si70O175)(OH,H2O,F)35, a new mineral from the Darai-Pioz alkaline massif, Tajikistan

Abstract 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-(Се), 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 Pm3̅, 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)Σ6{[(Nd9.57Ce6.13Sm2.39La2.20Pr1.68Gd0.93Eu0.27)Σ23.17(Ca3.90Sr2.87)Σ6.77]Σ29.94□0.06}Σ30(Si70.03O175)(OH14.47F6.54)Σ21.01(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.

Refinement of the crystal structure of berezanskite, Ti2□2KLi3(Si12O30)

Abstract Berezanskite, ideally Ti2□2KLi3(Si12O30), is hexagonal, space group P6/mcc, a = 9.898(4), c = 14.276(6) Å, V = 1211.2(9) Å3, 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, inwhich (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.

Tatarinovite Са3Al(SO4)[В(ОH)4](ОH)6 · 12H2O, a new ettringite-group mineral from the Bazhenovskoe deposit, Middle Urals, Russia, and its crystal structure

A new mineral, tatarinovite, ideally Са3Аl(SO4)[В(ОН)4](ОН)6 · 12Н2O, has been found in cavities of rhodingites at the Bazhenovskoe chrysotile asbestos deposit, Middle Urals, Russia. It occurs (1) colorless, with vitreous luster, bipyramidal crystals up to 1 mm across in cavities within massive diopside, in association with xonotlite, clinochlore, pectolite and calcite, and (2) as white granular aggregates up to 5 mm in size on grossular with pectolite, diopside, calcite, and xonotlite. The Mohs hardness is 3; perfect cleavage on (100) is observed. Dmeas = 1.79(1), Dcalc = 1.777 g/cm3. Tatarinovite is optically uniaxial (+), ω = 1.475(2), ε = 1.496(2). The IR spectrum contains characteristic bands of SO42−, CO32−, B(OH)4−, B(OH)3, Al(OH)63-, Si(OH)62-, OH–, and H2O. The chemical composition of tatarinovite (wt %; ICP-AES; H2O was determined by the Alimarin method; CO2 was determined by selective sorption on askarite) is as follows: 27.40 CaO, 4.06 B2O3, 6.34 A12O3, 0.03 Fe2O3, 2.43 SiO2, 8.48 SO3, 4.2 CO2, 46.1 H2O, total is 99.04. The empirical formula (calculated on the basis of 3Ca apfu) is H31.41Ca3.00(Al0.76Si0.25)Σ1.01 · (B0.72S0.65C0.59)Σ1.96O24.55. Tatarinovite is hexagonal, space gr. P63, a = 11.1110(4) Å, c = 10.6294(6) Å, V = 1136.44(9) A3, Z = 2. Its crystal chemical formula is Са3(Аl0.70Si0.30) · {[SO4]0.34[В(ОН)4]0.33[СO3]0.24}{[SO4]0.30[В(ОН)4]0.34[СО3]0.30[В(ОН)3]0.06}(ОН5·73О0.27) · 12Н2O. The strongest reflections of the powder X-ray diffraction pattern [d, Å (I, %) (hkl)] are 9.63 (100) (100), 5.556 (30) (110), 4.654 (14) (102), 3.841 (21) (112), 3.441 (12) (211), 2.746 (10) (302), 2.538 (12) (213). Tatarinovite was named in memory of the Russian geologist and petrologist Pavel Mikhailovich Tatarinov (1895–1976), a well-known specialist in chrysotile asbestos deposits. Type specimens have been deposited at the Fersman Mineralogical Museum of the Russian Academy of Sciences, Moscow.

Formation of baotite in alcaline rocks of a moraine of Dara-i-Pioz glacier, Tadjikistan

Unusual baotite aggregates were found among boulders, bearing alcaline mineralization at a moraine of the Dara-i-Pioz glacier, Tadjikistan. Baotite forms intergrowths with barylite and berezanskite (association # 1) and with quartz in tienshanite (Tn), as well as radial needle splitted crystals in tienshanite voids (association #2). Electron microprobe analysis gives (wt %, assoc. # 1/assoc. #2): SiO 2 15.65/15.80, TiO 2 41.05/36.97, Nb 2 O 5 0.72/2.70, Fe 2 O 3 0.33/1.21, Al 2 O 3 0.14/1.21, PbO 1.39/ -, BaO 37.96/38.14, Cl 2.46/2.29, MnO, CaO, Na 2 O, K 2 O - traces, total 99.24/98.17. Optically uniaxial, positive, ω = 1.940(5), e > 2.00. Six strongest lines in the X-ray powder diffraction pattern are (d o b s . , I): 3.73(6), 3.52(6), 3.32(8), 2.92(5), 2.236(10), 1.334(4). The origin of the baotite (Baot), associated with tienshanite (Tn) appears to result from the hydrothermal alteration. A possible reaction is: 8Tn + Cl - = lBaot + 44Qv + 8(2Na + , Mn + 2 , 2B + 3 , 5.5O - 2 ).

Odigitriaite, CsNa5Ca5[Si14B2O38]F2, a new caesium borosilicate mineral from the Darai-Pioz alkaline massif, Tajikistan: Description and crystal structure

Abstract 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-(Се), 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]F-. 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) (3̅ 1 3), 3.95 (25) (3 1 3), 2.85 (31) (2 2 2), 2.68 (40) (0 0 6), 3.62 (45) (0 2 4), 3.35 (100) (2̅ 2 4), 3.31 (30) (3̅ 1 5), 3.25 (35) (4 0 4), 3.04 (60) (4̅ 2 2), 2.925 (22) (4̅ 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.