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A detailed investigation was conducted on high-pressure (~1.4 GPa) tourmaline from an Eoalpine mafic eclogite, which occurs in the Kreuzeck Mountains, Eastern Alps, Austria. Tourmaline from this locality contains the highest amount of Sr²⁺ (up to 0.68 wt% SrO) known to date. The space group is R3m with unit-cell parameters a = 15.944(1), c = 7.202(1) Å, V = 1585.5(3) ų. Analyses by a combination of electron microprobe, optical absorption spectroscopy and crystal-structure refinement (R1 = 1.31%) result in the structural formula ^X(Na_(0.85)Ca_(0.08)Sr_(0.06)K_(0.01))_(Σ1.00)^Y(Mg_(1.68)Al_(0.70) Fe_(0.37)³⁺Ti_(0.10)⁴⁺Fe_(0.11)²⁺Ca_(0.03)Cr_(0.01)³⁺)_(Σ3.00)^Z (Al_(5.15)Mg_(0.80)Fe_(0.05)³⁺)_(Σ6.00)^T(Si_(5.82)B_(0.10)Al_(0.08)O_(18)) (BO₃)₃^V(OH)₃^W [O_(0.45)(OH)_(0.35)F_(0.20)]. The T site contains mainly Si and additionally small amounts of B and Al. According to optical absorption spectroscopy (using the band near 1120 nm), the Fe³⁺/Fe ratio is 79 ± 2%, suggesting that this high-pressure tourmaline crystallized under oxidizing conditions. It has a significant oxy-dravite component. A near-rim zone contains 0.6 wt% Cr₂O₃, 0.5 wt% PbO₂, 0.2 wt% NiO and 0.1 wt% V₂O₃. Only a small F content was found by structure refinement. There is no evidence for significant X-site vacancy in the investigated tourmaline zones. We assume that the original boron source for tourmaline crystallization in the eclogite, i.e. tourmaline-bearing pegmatites in the country-rock, were influenced by a Sr-bearing marble.

Single crystals with dimensions up to 20 × 20 × 20 mm3 of 11 new bis(alkylammonium) zirconium bis(nitrilotriacetates) have been grown from aqueous solutions. Their elastic and thermoelastic properties were derived from ultrasonic resonant frequencies of plane-parallel plates and their shift upon variation of temperature, respectively. All of these crystal species belong to the monoclinic or orthorhombic crystal systems. The majority possesses an acentric crystal structure giving rise to piezoelectric effects, which surmount the maximum longitudinal piezoelectric effect d 111 of α-quartz by a factor of two. The pyroelectric effect of two of these specimens is about three to four times larger than π 3 σ $\pi _3^\sigma $ of tourmaline. In addition, the tensors of thermal expansion were determined. Owing to the dominating large size of the anion most physical properties of the salts with different cations behave quite similar. Branched or more globular alkylammonium cations generate a slightly larger mean elastic stiffness than unbranched cations.

Three new, isotypic silicate compounds, BaY4(Si2O7)(Si3O10), SrYb4(Si2O7)(Si3O10) and SrSc4(Si2O7)(Si3O10), were synthesized using high-temperature flux growth techniques, and their crystal structures were solved from single-crystal X-ray intensity data: monoclinic, P21/m, with a=5.532(1)/5.469(1)/5.278(1), b=19.734(4)/19.447(4)/19.221(4), c=6.868(1)/6.785(1)/6.562(1) A, β=106.53(3)/106.20(3)/106.50(3)°, V=718.8(2)/693.0(2)/638.3(2) A3, R(F)=0.0225/0.0204/0.0270, respectively. The topology of the novel structure type contains isolated horseshoe-shaped Si3O10 groups (Si–Si–Si=93.15–95.98°), Si2O7 groups (Si–Obridge–Si=180°, symmetry-restricted) and edge-sharing M(1)O6 and M(2)O6 octahedra. Single-crystal Raman spectra of the title compounds were measured and compared with Raman spectroscopic data of chemically and topologically related disilicates and trisilicates, including BaY2(Si3O10) and SrY2(Si3O10). The band assignments are supported by additional theoretical calculation of Raman vibrations by DFT methods.

Fe^(2+)- and Mn^(2+)-rich tourmalines were used to test whether Fe^(2+) and Mn^(2+) substitute on the Z site of tourmaline to a detectable degree. Fe-rich tourmaline from a pegmatite from Lower Austria was characterized by crystal-structure refinement, chemical analyses, and Mössbauer and optical spectroscopy. The sample has large amounts of Fe^(2+) (~2.3 apfu), and substantial amounts of Fe^(3+) (~1.0 apfu). On basis of the collected data, the structural refinement and the spectroscopic data, an initial formula was determined by assigning the entire amount of Fe^(3+) (no delocalized electrons) and Ti^(4+) to the Z site and the amount of Fe^(2+) and Fe^(3+) from delocalized electrons to the Y-Z ED doublet (delocalized electrons between Y-Z and Y-Y): X(Na_(0.9)Ca_(0.1)) ^Y(Fe^(2+)_(2.0)Al_(0.4)Mn^(2+)_(0.3)Fe^(3+)_(0.2)) ^Z(Al_(4.8)Fe^(3+)_(0.8)Fe^(2+)_(0.2)Ti^(4+)_(0.1)) ^T(Si_(5.9)Al_(0.1))O_(18) (BO_3)_3^V(OH)_3 ^W[O_(0.5)F_(0.3)(OH)_(0.2)] with α = 16.039(1) and c = 7.254(1) Å. This formula is consistent with lack of Fe^(2+) at the Z site, apart from that occupancy connected with delocalization of a hopping electron. The formula was further modified by considering two ED doublets to yield: ^X(Na_(0.9)Ca_(0.1)) ^Y(Fe^(2+)_(1.8)Al_(0.5)Mn^(2+)_(0.3)Fe^(3+)_(0.3)) ^Z(Al_(4.8)Fe^(3+)_(0.7)Fe^(2+)_(0.4)Ti^(4+)_(0.1)) ^T(Si_(5.9_Al_(0.1))O_(18) (BO_3)_3 ^V(OH)_3 ^W[O_(0.5)F_(0.3)(OH)_(0.2)]. This formula requires some Fe^(2+) (~0.3 apfu) at the Z site, apart from that connected with delocalization of a hopping electron. Optical spectra were recorded from this sample as well as from two other Fe^(2+)-rich tourmalines to determine if there is any evidence for Fe^(2+) at Y and Z sites. If Fe^(2+) were to occupy two different 6-coordinated sites in significant amounts and if these polyhedra have different geometries or metal-oxygen distances, bands from each site should be observed. However, even in high-quality spectra we see no evidence for such a doubling of the bands. We conclude that there is no ultimate proof for Fe^(2+) at the Z site, apart from that occupancy connected with delocalization of hopping electrons involving Fe cations at the Y and Z sites. A very Mn-rich tourmaline from a pegmatite on Elba Island, Italy, was characterized by crystal-structure determination, chemical analyses, and optical spectroscopy. The optimized structural formula is ^X(Na_(0.6)□_(0.4)) ^Y(Mn^(2+)_(1.3)Al_(1.2)Li_(0.5)) ^ZAl_6 ^TSi_6O_(18) (BO_3)_3 ^V(OH)_3 ^W[F_(0.5)O_(0.5)], with α = 15.951(2) and c = 7.138(1) Å. Within a 3σ error there is no evidence for Mn occupancy at the Z site by refinement of Al ↔ Mn, and, thus, no final proof for Mn^(2+) at the Z site, either. Oxidation of these tourmalines at 700–750 °C and 1 bar for 10–72 h converted Fe^(2+) to Fe^(3+) and Mn^(2+) to Mn^(3+) with concomitant exchange with Al of the Z site. The refined ^ZFe content in the Fe-rich tourmaline increased by ~40% relative to its initial occupancy. The refined YFe content was smaller and the distance was significantly reduced relative to the unoxidized sample. A similar effect was observed for the oxidized Mn^(2+)-rich tourmaline. Simultaneously, H and F were expelled from both samples as indicated by structural refinements, and H expulsion was indicated by infrared spectroscopy. The final species after oxidizing the Fe^(2+)-rich tourmaline is buergerite. Its color had changed from blackish to brown-red. After oxidizing the Mn^(2+)-rich tourmaline, the previously dark yellow sample was very dark brown-red, as expected for the oxidation of Mn^(2+) to Mn^(3+). The unit-cell parameter α decreased during oxidation whereas the c parameter showed a slight increase.

Crystal structures, chemical (including light elements) and spectral data (optical and Mossbauer spectroscopies) were used to characterize coloured (brown, pink, green) tourmalines from three granitic pegmatites from the Moldanubian nappes (Konigsalm, Maigen and Blocherleitengraben; Lower Austria). The tourmalines can be classified as fluor-schorl, schorl, foitite, magnesiofoitite, olenite and "fluor-elbaite" with varying Li contents, up to ~ 1.2 wt% Li_2O. Coexisting minerals are quartz, plagioclase (up to An_7), microcline, garnet (spessartine-almandine), muscovite, biotite (annite), very rare lepidolite, apatite, monazite-(Ce), xenotime-(Y), allanite-(Ce) and zircon. The chemical composition of the Fe^(2+)-rich tourmaline samples (up to ~ 1.0 wt% TiO_2) varies from fluorschorl, with α = 15.987(2), c = 7.163(2) A to ^X(_(0.63)Na_(0.37)) ^Y(Fe^(2+)_(1.12)Al_(1.09)Mg_(0.56)Mn^(2+)_(0.08)Fe^(3+) _(0.07)Li_(0.02)Ti^(4+)_(0.01)Zn_(0.01)_(0.04)) ^Z(Al_(5.74)Mg_(0.26)) (BO_3)_3 [Si_(5.96)Al_(0.04)O_(18)] ^V(OH)_3 ^W[(OH)_(0.95)F_(0.05)], strongly dichroic (pink and blue) foitite, with α 15.9537(2), c = 7.1448(4) A, to ^X(_(0.51)Na_(0.49)) ^Y(Fe^(2+)_(0.97)Al_(0.93)Mg_(0.75)Fe^(3+)_(0.23)Mn^(2+) _(0.04)Li_(0.01)Ti^(4+)_(0.01)_(0.06))^Z(Al_(5.72)Mg_(0.28)) (BO_3)_3 [Si_(5.95)Al_(0.05)O_(18)]^V(OH)_3^W[(OH)_(0.91)O_(0.06)F_(0.03)], magnesiofoitite, with α = 15.9476(4), c = 7.1578(4) A. The chemical composition of the Al- and Lirich and Mn^(2+)-bearing (up to ~ 5.7 wt% MnO) samples varies from ^X(Na_(0.84)Ca_(0.02)_(0.14))^Y(Al_(1.35)Li_(0.78)Mn^(2+) _(0.65)Ti^(4+)_(0.01)_(0.21))^ZAl_6(BO_3)_3[Si_(5.92)Al_(0.04)B_(0.04)O_(18)]^V(OH)_3^W[F_(0.81)(OH)_(0.19)], "fluor-elbaite" with α = 15.8887(3), c = 7.1202(3) A, to ^X(Na_(0.76)Ca_(0.12)_(0.12))^Y(Al_(1.52)Li_(0.69)Mn^(2+) _(0.43)Fe^(2+)_(0.09)_(0.27))^ZAl_6(BO_3)_3 [Si_(5.71)B_(0.29)O_(18)]^V(OH)_3^W[F_(0.69)(OH)_(0.31)], B-rich "fluorelbaite", with α = 15.8430(3), c = 7.1051(3)A. A positive correlation between the and bond lengths in tourmalines where the Z site is only occupied by Al (R^2 = 0.617) is useful to correct the bond length for the inductive effect of the varying bond length. This is important for producing accurate assignments for the different 6-coordinated sites in tourmaline. On the basis of Sm-Nd (garnet, monazite), U-Th-Pb, and U-Pb ages (monazite), the pegmatites crystallised during the Variscan tectonometamorphic event in the Visean (339 4 Ma Maigen, 332 3 Ma Konigsalm). These ages are in the range of the earliest intrusions of the South Bohemian pluton (Rastenberg type durbachites). However, on the basis of the spatial relationship of the pegmatites and the Rastenberg type intrusions, a linkage of the intrusive body and the pegmatites is unlikely. Alternatively, the pegmatites may have evolved as granitic pegmatitic melts during decompression from the surrounding country rocks in the frame of exhumation of the Moldanubian nappes after the peak of the Variscan metamorphism.

Hezuolinite is a new mineral species occurring as an accessory mineral in the Saima alkaline complex in Liaoning Province, NE China. The mineral occurs in a green-aegirine nepheline syenite as non-metamict grains and is associated with microcline, nepheline, aegirine, biotite, eudialyte, rinkite and titanite. The anhedral crystals are several hundred micrometres in size. The mineral is black with dark-brown streak. It is translucent with a resinous luster. Cleavage or parting was not observed. It is brittle with a conchoidal fracture. The hardness is VHN 100 683–964 kg mm −2 (5.5–6 on Mohs’ scale). The measured density is 4.28 g cm −3 , and the calculated value is 4.30 g cm −3 from the empirical chemical formula. Optically, hezuolinite is biaxial negative, with n > 1.8 and 2V = 75°. The dispersion is strong with r > v . The mineral shows a strong pleochroism, from pale brown to dark brown. The average of twenty-five analyses leads to the empirical formula (Sr 2.15 Ce 0.55 La 0.49 Ca 0.49 Na 0.12 Nd 0.09 Pr 0.03 Th 0.03 Sm 0.01 Eu 0.01 ) ∑3.98 (Zr 0.82 Fe 2+ 0.14 Hf 0.02 Mn 0.01 ) ∑1.00 (Ti 1.38 Fe 3+ 0.36 Fe 2+ 0.14 Al 0.04 Nb 0.02 ) ∑1.94 Ti 2 O 8 (Si 2.01 O 7 ) 2 , on the basis of O = 22. The simplified formula is (Sr, REE ) 4 Zr(Ti,Fe 3+ ,Fe 2+ ) 2 Ti 2 O 8 (Si 2 O 7 ) 2 , ideally Sr 2 REE 2 Zr(Fe 2+ )Ti 3 O 8 (Si 2 O 7 ) 2 . The five strongest reflections in the X-ray powder-diffraction pattern [ d in A (I)( hkl )] are: 2.98(100)(−204), 3.02(90)(−313), 1.96(90)(024), 2.18(40)(−422), and 2.84(70)(020). The structure was solved and refined in space group C 2/ m , with a = 13.973(3), b = 5.6984(11), c = 11.988(2) A, β = 114.10(1) °, V = 871.3(3) A 3 , Z = 2, to R1 = 0.037, wR2 = 0.097. The structure of hezuolinite is similar to rengeite. The changes of Sr-O, Zr-O and Ti(1)-O distances confirm partial substitutions of REE for Sr, and Fe for Ti. The sites of O(1), O(2) and O(3) of the hezuolinite structure ( C 2/ m ) are split into O(1) and O(1′), O(2) and O(2′), O(3) and O(3′) sites in the rengeite structure ( P 2 1 / a ), respectively. The Si(1)-O(7)-Si(2) angle in hezuolinite is 175.8°, and is significantly less bent than in rengeite (169.7°). The observed systematic extinctions are in agreement with space group C 2/ m . Hezuolinite is a member of the perrierite-subgroup and can be considered as a chemical intermediate between rengeite and perrierite.

Chemical and structural variations of 11 minerals of the cancrinite group having an Al,Si,O framework of the AB type are summarized and discussed. The total number of chemically studied samples is 360 (our data and literature data): cancrinite 192 and 35, vishnevite 21 and 13, cancrisilite 19 and 10, kyanoxalite and oxalate-rich intermediate members of the cancrinite– kyanoxalite series 12 and 0, davyne 10 and 23, depmeierite 2 and 0, balliranoite 1 and 0, hydroxycancrinite 0 and 1, quadridavyne 0 and 10, microsommite 0 and 8, and pitiglianoite 0 and 3. We provide original structural data for nine samples of distinct varieties of cancrinite and one sample of cancrisilite, as well as published structural data on the above-listed minerals. The major topics are the distribution and ratios of extra-framework components, cations (Na + , Ca 2+ , K + ), anions (CO 3 2− , SO 4 2− , Cl − , C 2 O 4 2− , PO 4 3− ) and H 2 O, with special emphasis on oxalate and phosphate anions. The idealized formula of cancrinite has been refined: Na 7 Ca[Al 6 Si 6 O 24 ](CO 3 ) 1.5 •2H 2 O. The solid-solution series with coupled substitutions in the framework and extra-framework portions are discussed, as is the genetic aspect of crystal chemistry of cancrinite-group minerals with a AB -type framework.

Elpidite Na2ZrSi6O15 · 3H2O [space group Pbcm, a = 7.1312(12), b = 14.6853(12), and c = 14.6349(15) A] from Khan Bogdo (Mongolia) and its K- and Rb-exchanged forms K1.78Na0.16H0.06ZrSi6O15 · 0.85H2O [Cmce, a = 14.054(3), b = 14.308(3), and c = 14.553(3) A] and Na1.58Rb0.2H0.22ZrSi6O15 · 2.69H2O [Pbcm, a = 7.1280(10), b = 14.644(3), and c = 14.642(3) A] that were obtained by cation exchange at 90°C, as well as K1.84Na0.11H0.05ZrSi6O15 · 0.91H2O [Cmce, a = 14.037(3), b = 14.226(3), and c = 14.552(3) A] and Rb1.78Na0.06H0.16ZrSi6O15 · 0.90H2O [Cmce, a = 14.2999(12), b = 14.4408(15), and c = 14.7690(12) A], obtained at 150°C are studied by single-crystal X-ray diffraction and IR spectroscopy. The base of the structures is a heteropolyhedral Zr-Si-O framework whose cavities accommodate Na (K, Rb) cations and H2O molecules.

Nanlingite was first described as a new mineral from a dolomitic limestone along a contact between greisenized granite and dolomitic limestone in the Nanling area, Hunan Province, China. The structure was solved and refined on single-crystal X-ray data in space group R 3 m , with a = 10.2114(10), c = 25.689(3) A, V = 2319.2(6) A 3 , to R1 = 0.021, wR2 = 0.049. The chemical formula of nanlingite is Na(Ca, Li, Na) 6 (Mg, Fe) 12 (AsO 3 ) 2 [Fe(AsO 3 ) 6 ] F 14 with Z = 3 according to the crystal structure refinement. The complex framework is formed by edge- and corner-sharing of distorted NaF 8 and CaF 4 O 4 cubes, MgF 2 O 4 octahedra, and AsO 3 trigonal pyramids. The lithium atom occupies (22 %) the split site at 0.58(2) A from the main Ca site and exhibits a five-fold coordination with 2.21 A. The iron atom (at 3 b , site symmetry 3m) is surrounded by six As atoms of AsO 3 groups at a distance of 2.40 A with the lone-pair electrons pointing towards the central atom. This [Fe(AsO 3 ) 6 ] cluster is a novel configuration in the crystal chemistry of minerals. According to Mossbauer spectra and electron energy-loss spectroscopy data the oxidation state of Fe in nanlingite is mainly Fe II with a low-spin state. In the configuration of arsenite groups, the distance = 1.73 A of the [Fe(AsO 3 ) 6 ] clusters is shorter than the normal range. The empirical crystal-chemical formula for nanlingite is (Na 0.90 Li 0.10 )∑ 1.00 (Ca 4.41 Li 1.06 Mg 0.17 Na 0.06 Mn 0.05 □ 0.25 )∑ 6.00 (Mg 11.38 Fe 3+ 0.30 Al 0.29 Ti 0.03 )∑ 12.00 (AsO 3 ) 2 [Fe II (AsO 3 ) 6 ](F 13.77 OH 0.16 )∑ 13.93 .

The new, non-centrosymmetric chain silicate, K2.9Rb0.1ErSi3O9, was prepared by a high-temperature flux-growth technique, and its crystal structure was determined from single-crystal X-ray intensity data (Mo-Kα, 293 K) in space P1, with a = 6.672(1), b = 6.719(1), c = 6.725(1) Å, α = 108.87(3), β = 106.72(3), γ = 107.61(3)°, V = 245.82(6) Å3, Z = 1, R(F) = 2.81%. The compound represents a novel structure type. K2.9Rb0.1ErSi3O9 is characterized by a mixed octahedral-tetrahedral framework, in which each corner of the isolated ErO6 octahedron ( = 2.26 Å) is linked to infinite [Si3O9] chains extending approximately along [111]. This connectivity results in a microporous character with two different, narrow channels that extend parallel to [111] and [100] and host K+ cations. The atomic arrangement is strongly pseudorhombohedral. A single-crystal Raman spectrum of K2.9Rb0.1ErSi3O9 is in agreement with the low space-group symmetry. Relations to minerals and synthetic compounds based on [Si3O9] chains are discussed, revealing that the geometry of the chain in K2.9Rb0.1ErSi3O9 is similar to that in pectolite, NaCa2[HSi3O9].

A new lead iron(III) hydrated phosphate, Pb 3 Fe 2 (PO 4 ) 4 (H 2 O), has been synthesised hydrothermally in Teflon-lined stainless steel autoclaves at 220 °C for 7 days, with an initial pH of 1.5. It is the first example of a synthetic hydrous Pb–Fe 3+ phosphate. Crystals are small, colourless to white prisms, uniaxial (+) and non-pleochroic. The calculated refractive index for white light is n = 1.95. Single-crystal structure determination ( R ( F ) = 0.0457) shows Pb 3 Fe 2 (PO 4 ) 4 (H 2 O) to be tetragonal, space group P 4 1 2 1 2 (no. 92), with a = 9.0440(10), c = 16.766(3) A, V = 1371.4(3) A 3 and Z = 4. Pb 3 Fe 2 (PO 4 ) 4 (H 2 O) has a structure type which is based on a tetrahedral–octahedral framework of FeO 6 octahedra sharing corners with PO 4 tetrahedra, with Pb atoms and H 2 O molecules occupying voids in the framework. Pb 3 Fe 2 (PO 4 ) 4 (H 2 O) is homeotypic with synthetic Pb 3 Cr 2 (PO 4 ) 4 ; both compounds share the same heteropolyhedral topology and the same space group, but only Pb 3 Fe 2 (PO 4 ) 4 (H 2 O) contains an additional position occupied by a water molecule. The octahedral–tetrahedral chain of Pb 3 Fe 2 (PO 4 ) 4 (H 2 O) is topologically similar to double–strand chains found in the structures of hannayite, galliskiite, kapundaite, PbIn(AsO 4 )(AsO 3 OH) and Na 2.88 Fe(PO 4 ) 2 . Infrared spectroscopy is used to describe the vibrational properties of Pb 3 Fe 2 (PO 4 ) 4 (H 2 O).

Heftetjernite, ideally ScTaO 4 , is a new scandium mineral from the Heftetjern pegmatite, Tordal, Telemark, Norway. In the type specimen, it occurs as minute, elongate tabular, very dark brown crystals in a single small void in albite. Other associated minerals are fluorite, muscovite, altered milarite, a metamict, dark greyish brown mineral of the pyrochlore-microlite group, and an unidentified, orange-brown, tabular, nearly X-ray amorphous Ti-Y-Ta-Nb-mineral. Electron-microprobe analysis yielded the empirical formula (Sc 0.64 Sn 0.13 Mn 0.12 Fe 0.08 Ti 0.06 ) ∑1.03 (Ta 0.69 Nb 0.30 ) ∑0.99 O 4 which clearly demonstrates the charge-balanced substitution scheme 2Sc 3+ = (Sn,Ti) 4+ + (Mn,Fe) 2+ . The mineral crystallises in the wolframite structure type, with space group P 2/ c and a = 4.784(1), b = 5.693(1), c = 5.120(1) A, β = 91.15(3)°, V = 139.42(5) A 3 ( Z = 2). A synthetic equivalent is known. Strongest lines in the calculated X-ray powder diffraction pattern of heftetjernite are [ d in A( I ) ( hkl )]: 3.000 (100) (11–1), 2.9570 (97) (111), 3.662 (53) (110), 2.4877 (34) (02–1), 4.783 (33) (100), 3.807 (32) (01–1). The crystal structure was refined to R ( F ) = 1.39 % from single-crystal X-ray diffraction data (293 K). It is based on two types of edge-sharing, distorted octahedra occupied predominantly by Sc and Ta, respectively. Heftetjernite is translucent to transparent, with a dark brownish (with a reddish hue) streak and adamantine lustre. It is brittle, has a perfect {010} cleavage, irregular fracture and a Mohs hardness estimated to be around 4.5 by comparison to ferberite; D x = 6.44 g/cm 3 (from crystal-structure analysis). Optically, the mineral is biaxial with an unknown optical sign, weakly pleochroic (yellowish brown with a reddish tint to reddish brown), with no observable dispersion. A mean refractive index of 2.23 was calculated from the Gladstone-Dale relationship using the X-ray density. Heftetjernite is named after its type locality. The mineral is compared with synthetic ScTaO 4 , ScNbO 4 , iwashiroite-(Y) and formanite-(Y) (both nominally YTaO 4 ), and some comments are made on the relation to Sc-bearing ixiolite.

Five new mixed-framework trisilicates were synthesised using a high-temperature flux growth technique. Colourless, glassy plates of SrY 2 Si 3 O 10 crystallise in space group P 1, with a = 6.757(1), b = 6.885(1), c = 9.273(2) A, α = 72.42(3), β = 86.37(3), γ = 88.37(3)°, V = 410.38(12) A 3 , Z = 2. The main building units of the new structure type represented by SrY 2 Si 3 O 10 are slightly curved Si 3 O 10 trimers and Y 2 O 11 dimers (composed of YO 6 octahedra sharing an edge with YO 7 polyhedra), which are further edge-connected to adjacent dimers to form twisted zigzag chains parallel to [010]. BaREE 2 Si 3 O 10 (REE = Gd, Er, Yb, Sc) form colourless small prisms, pseudohexagonal plates or isometric crystals, and crystallise in space group P 2 1 / m , with respectively a = 5.435(1) / 5.389(1) / 5.377(1) / 5.273(1), b = 12.241(2) / 12.163(2) / 12.117(2) / 11.918(2), c = 6.932(1) / 6.840(1) / 6.790(1) / 6.591(1) A, β = 106.26(3) / 106.47(3) / 106.50(3) / 107.06(3)°, V = 442.74(13) / 429.94(12) / 424.17(12) / 395.98(12) A 3 , Z = 2. BaREE 2 Si 3 O 10 (REE = Gd, Er, Yb, Sc) are isotypic with BaY 2 Si 3 O 10 . Their topology is characterised by horseshoe-shaped trisilicate (Si 3 O 10 ) groups and zigzag chains of edge-sharing distorted M O 6 octahedra ( M = Gd, Er, Yb, Sc). Correlations between β –, Si–Si–Si angle and unit-cell volume and REE 3+ ionic radii are discussed. The geometries of the Si 3 O 10 and T 3 O 10 groups ( T = Ge, P, As, Al, Ga, V) in non-silicates are briefly reviewed, with special focus on narrow Si–Si–Si angles.

The title compound, dibarium digadolinium(III) tetrasilicate, crystallized from a molybdate-based flux. It represents a new structure type and contains finite zigzag-shaped C(2)-symmetric Si(4)O(13) chains and Gd(2)O(12) dimers built of edge-sharing GdO(7) polyhedra. The [9+1]-coordinated Ba atoms are located in voids in the atomic arrangement. All atoms are in general positions except for one O atom, which lies on a twofold axis. The structure is compared with those of the few other known tetrasilicates.

Three new scandium silicates with framework structures made of octahedra and tetrahedra, KSrScSi2O7, NaBaScSi2O7 and RbBaScSi3O9, were obtained through a high-temperature flux-growth technique. Their crystal structures have been determined from single-crystal intensity data (Mo K α radiation, CCD area detector, 293 K; R ( F ) = 3.30, 1.82, 2.00%, respectively). The disilicate KSrScSi2O7 is monoclinic, P 21/ n , with a 9.446(2), b 5.478(1), c 12.537(3) A, β 104.39(3)°, V 628.4(2) A3, Z = 4. The disilicate NaBaScSi2O7 forms monoclinic crystals with space-group symmetry P 21/ m , with a 6.845(1), b 5.626(1), c 8.819(2) A, β 109.33(3)°, V 320.47(10) A3, Z = 2. The cyclosilicate RbBaScSi3O9 crystallizes as pseudohexagonal triplets; it is also monoclinic, P 21/ n , with a 6.957(1), b 10.199(2), c 11.881(2) A, β 90.07(3)°, V 843.0(2) A3, Z = 4. The topologies of KSrScSi2O7 and NaBaScSi2O7 show clear similarities, corresponding to isolated Si2O7 groups, bound to octahedrally coordinated Sc3+. The pseudohexagonal arrangement in RbBaScSi3O9 is based on isolated ScO6 octahedra, each of which is corner-linked to Si3O9 rings. In all three compounds, the alkali and alkaline-earth atoms occupy voids in the resulting three-dimensional frameworks. Results of a Raman spectroscopic study of the two disilicates and of five related novel disilicates are also briefly presented, with a focus on the behavior of the Si2O7 group.

Tourmaline grains extrcted from rocks within three ultrahigh-pressure (UHP) metamorphic localities have been subjected to a structurally and chemically detailed analysis to test for any systematic behavior related to temperature and pressure. Dravite from Parigi, Dora Maira, Western Alps (peak P - T conditions ~3.7 GPa, 750 °C), has a structural formula of X(Na0.90Ca0.05K0.01□0.04)Y(Mg1.78Al0.99Fe2+0.12Ti4+0.03□0.08)Z(Al5.10Mg0.90)(BO3)3TSi6.00O18V(OH)3W[(OH)0.72F0.28]. Dravite from Lago di Cignana, Western Alps, Italy (~2.7–2.9 GPa, 600–630 °C), has a formula of X(Na0.84Ca0.09K0.01□0.06)Y(Mg1.64Al0.79Fe2+0.48Mn2+0.06Ti4+0.02Ni0.02Zn0.01)Z(Al5.00Mg1.00)(BO3)3T(Si5.98Al0.02)O18V(OH)3W[(OH)0.65F0.35]. “Oxy-schorl” from the Saxonian Erzgebirge, Germany (≥4.5 GPa, 1000 °C), most likely formed during exhumation at >2.9 GPa, 870 °C, has a formula of X(Na0.86Ca0.02K0.02□0.10)Y(Al1.63Fe2+1.23Ti4+0.11Mg0.03Zn0.01) Z(Al5.05Mg0.95)(BO3)3T(Si5.96Al0.04)O18V(OH)3W[O0.81F0.10(OH)0.09]. There is no structural evidence for significant substitution of [4]Si by [4]Al or [4]B in the UHP tourmaline ( distances ~1.620 A), even in high-temperature tourmaline from the Erzgebirge. This is in contrast to high- T –low- P tourmaline, which typically has significant amounts of [4]Al. There is an excellent positive correlation ( r 2 = 1.00) between total [6]Al (i.e., YAl + ZAl) and the determined temperature conditions of tourmaline formation from the different localities. Additionally, there is a negative correlation ( r 2 = 0.97) between F content and the temperature conditions of UHP tourmaline formation and between F and YAl content ( r 2 = 1.00) that is best explained by the exchange vector YAlO(R2+F)−1. This is consistent with the W site (occupied either by F, O, or OH), being part of the YO6-polyhedron. Hence, the observed Al-Mg disorder between the Y and Z sites is possibly indirectly dependent on the crystallization temperature.

Chemical, structural, infrared, optical, and Mossbauer spectroscopic data were obtained on tourmalines from gem pockets in the Himalaya mine, San Diego County, California, including a strongly color-zoned crystal. Calcium and Li abundances increase from core to rim, whereas Mn^(2+) and F increase, reach a maximum, and then decrease. Upon initiation of crystallization of lepidolite, F contents in tourmaline decrease. The black core is a Mn-bearing "oxy-schorl." The grayish-yellow, intermediate zone is Mn-rich "fluor-elbaite" that contains a relatively high Mn content with ~6 wt% MnO. The nearly colorless "fluor-elbaite" rim has the highest Li content of all zones. There is an inverse correlation between the lattice parameter a (for values ≥ 15.84 A) and the Li content (r^2 = 0.96). Mossbauer studies from the different zones within this crystal show that the Fe^(3+)/Fe(total) ratio increases continuously from the Fe-rich core to the Fe-poor near-rim zone, consistent with increasing oxygen fugacity during pegmatite pocket evolution. There is a high positive correlation between lattice parameter a (for values ≥ 15.84 A) and (Fe^(2+) + Mn^(2+)) content in tourmalines from the elbaite-schorl series (r^2 = 0.99). Values lower than 15.84 A for a are likely a consequence of greater ^([4])B contents in samples that usually have a (Fe^(2+) + Mn^(2+)) content of

Pale-blue to pale-green tourmalines from the contact zone of Permian pegmatites to mica schists and marbles from different localities of the Austroalpine basement units (Rappold Complex) in Styria, Austria, are characterized. All these Mg-rich tourmalines have small but significant Li contents, up to 0.29 wt% Li2O, and can be characterized as dravite, with FeO contents of ~ 0.9–2.7 wt%. Their chemical composition varies from X(Na0.67Ca0.19 K0.02☐0.12) Y(Mg1.26Al0.97Fe2+0.36Li0.19Ti4+0.06Zn0.01☐0.15) Z(Al5.31 Mg0.69) (BO3)3 Si6O18V(OH)3 W[F0.66(OH)0.34], with a = 15.9220(3), c = 7.1732(2) A to X(Na0.67Ca0.24 K0.02☐0.07) Y(Mg1.83Al0.88Fe2+0.20Li0.08Zn0.01Ti4+0.01☐0.09) Z(Al5.25 Mg0.75) (BO3)3 Si6O18V(OH)3 W[F0.87(OH)0.13], with a = 15.9354(4), c = 7.1934(4) A, and they show a significant Al-Mg disorder between the Y and the Z sites (R1 = 0.013–0.015). There is a positive correlation between the Ca content and distance for all investigated tourmalines (r ≈ 1.00), which may reflect short-range order configurations including Ca and Fe2+, Mg, and Li. The tourmalines have XMg (XMg = Mg/Mg + Fetotal) values in the range 0.84–0.95. The REE patterns show more or less pronounced negative Eu and positive Yb anomalies. In comparison to tourmalines from highly-evolved pegmatites, the tourmaline samples from the border zone of the pegmatites of the Rappold Complex contain relatively low amounts of total REE (~8–36 ppm) and Th (0.1–1.8 ppm) and have low LaN/YbN ratios. There is a positive correlation (r ≈ 0.91) between MgO of the tourmalines and the MgO contents of the surrounding mica schists. We conclude that the pegmatites formed by anatectic melting of mica schists and paragneisses in Permian time. The tourmalines crystallized from the pegmatitic melt, influenced by the metacarbonate and metapelitic host rocks.

Florkeite is a new phillipsite-type zeolite. It was found in a Ca-rich xenolith from a quarry at the Bellerberg volcano near Ettringen, East Eifel volcanic area, Germany. The paragenesis includes tobermorite, thaumasite, willhendersonite, gismondine and ellestadite. It forms subparallel, short prismatic, pseudo-monoclinic crystals elongated along [100] and flattened on {010}, with a maximum length of 0.6 mm and a thickness of up to 0.1 mm. Additional forms are {100}, {001} and {201}. Florkeite is colourless, transparent, non-fluorescent and has a vitreous lustre and a white streak. It is brittle with irregular fracture, the calculated density is 2.266 gcm−3. Optically, it is biaxial negative with n α = 1.506(2), n β = 1.514(2), n γ = 1.518(2), 2 V = 71.0(5) ° at 589.3 nm and 297 K. No pleochroism is observed. Orientation of the indicatrix is X ∧ c = 43°, Y ∧ b = 40° and Z ∧ a = 8°. Electron microprobe analyses yielded (wt%): Na2O 2.32, K2O 10.29, MgO 0.04, CaO 8.43, Al2O3 30.20, SiO2 35.29, sum 86.57. A H2O content of 15.57 wt% was derived from the single-crystal structure refinement. The empirical formula calculated on the basis of Al + Si = 16 pfu is K2.96Ca2.04Na1.02 Mg0.01[Al8.03Si7.97O31.97] · 11.72H2O and the ideal formula can be given as K3Ca2Na[Al8Si8O32] · 12H2O. Florkeite is triclinic, space-group P 1 (no. 2), the unit-cell parameters in phillipsite-type setting are a = 19.965(1), b = 14.274(1), c = 8.704(1) A, α = 88.37(1), β = 125.08(1), γ = 89.57(1)°, V = 2028.2(3) A3, Z = 2 and the a : b : c ratio is 1.399 : 1 : 0.610. The five strongest lines in the powder X-ray diffraction pattern are ( d in A/ I obs): 3.235 / 100, 3.162 / 80, 3.135 / 80, 2.736 / 60, 4.956 / 45. The single-crystal structure refinement ( R 1 = 4.39 %) confirmed that the structure of florkeite is the triclinically distorted analogue of phillipsite with a complete (Al, Si) ordering at the T -sites of the framework (mean T (Al)–O: 1.731–1.743 A and T (Si)–O: 1.615–1.631 A), which reduces the topochemical symmetry to B 2/ b . The K+ cations are placed near the centre of 8-rings of the oto units, the Ca2+ and Na+ cations are located within the phi units. The doubling of the a -parameter and the reduction of the real symmetry to P 1 (is caused by an ordering of the extra-framework cations and H2O molecules within the 8-ring channel system along [100], basically Ca– □ –Ca, Na–Ca–Na and H2O–K–H2O. The (Al, Si) ordering is attributed to low-thermal genetic conditions within the Ca-rich xenolithic host, also indicated by the paragenesis with willhendersonite. Holotype material of florkeite has been deposited at the mineral collection of the Naturhistorisches Museum Wien, Austria. The mineral is named in honour of the German mineralogist and crystallographer Otto Wilhelm Florke (born 1926).

Friedrichbeckeite is a new milarite-type mineral. It was found in a single silicate-rich xenolith from a quarry at the Bellerberg volcano near Ettringen, eastern Eifel volcanic area, Germany. It forms thin tabular crystals flattened on {0001}, with a maximum diameter of 0.6 mm and a maximum thickness of 0.1 mm. It is associated with quartz, tridymite, augite, sanidine, magnesiohornblende, enstatite, pyrope, fluorapatite, hematite, braunite and roedderite. Friedrichbeckeite is light yellow, with white to light cream streak and vitreous lustre. It is brittle with irregular fracture and no cleavage, Mohs hardness of 6, calculated density is 2.686 gcm−3. Optically, it is uniaxial positive with nω = 1.552(2) and ne = 1.561(2) at 589.3 nm and a distinct pleochroism from yellow (//ω) to light blue (//e). Electron microprobe analyses yielded (wt.%): Na2O 2.73, K2O 4.16, BeO 4.67, MgO 11.24, MnO 2.05, FeO 1.76, Al2O3 0.15, SiO2 73.51, (Σ CaO, TiO2 = 0.06) sum 100.33 (BeO determined by LA-ICP-MS). The empirical formula based on Si = 12 is K0.87 Na0.86 (Mg1.57Mn0.28Fe0.24)Σ2.09 (Be1.83 Mg1.17)Σ3.00 [Si12O30], and the simplified formula can be given as K (□0.5Na0.5)2 (Mg0.8Mn0.1Fe0.1)2 (Be0.6 Mg0.4)3 [Si12O30]. Friedrichbeckeite is hexagonal, space-group P6/mcc, with a = 9.970(1), c = 14.130(3) A, V = 1216.4(3) A3, and Z = 2. The strongest lines in the X-ray powder diffraction pattern are (d in A / I obs / hkl): 3.180 / 100 / 121, 2.885 / 70 / 114, 4.993 / 30 / 110, 4.081 / 30 / 112, 3.690 / 30 / 022. A single-crystal structure refinement (R1 = 3.62 %) confirmed that the structure is isotypic with milarite and related [12] C [9] B 2 [6] A 2 [4] T23 [[4] T112O30] compounds. The C-site is dominated by potassium, the B-site is almost half occupied by sodium, and the A-site is dominated by Mg. The site-scattering at the T2-site can be refined to a Be/(Be + Mg) value close to 0.61; the T1-site is occupied by Si. Micro-Raman spectroscopy reveals an increasing splitting of scattering bands around 550 cm−1 for friedrichbeckeite. The mineral can be classified as an unbranched ring silicate or as a beryllo-magnesiosilicate. With respect to the end-member formula K (□0.5Na0.5)2 Mg2 Be3 [Si12O30] friedrichbeckeite represents the Mg-dominant analogue of almarudite, milarite or oftedalite. The mineral and its paragenesis were formed during pyrometamorphic modifications of the silicate-rich xenoliths enclosed in Quaternary leucite-tephritic lava of the Bellerberg volcano. Holotype material of friedrichbeckeite has been deposited at the mineral collection of the Naturhistorisches Museum Wien, Austria. The mineral is named friedrichbeckeite in honour of the Austrian mineralogist and petrographer Friedrich Johann Karl Becke (1855–1931).

Cation-exchange properties of natural hilairite, Na 2 {ZrSi 3 O 9 }· 3H 2 O, in aqueous salt solutions at 150 °C and the crystal structures of its Rb-, Ca-, Sr-, Ba- and Pb-exchanged forms have been studied on single crystals. All studied samples retain the mixed framework of “parent” hilairite consisting of helical chains [Si 3 O 9 ] ∞ linked by isolated [ZrO 6 ] octahedra. The main differences between the crystal structures of these cation-exchanged forms of hilairite and other representatives of the hilairite group are connected with the number and positions of extra-framework cations and water molecules, framework distortion, unit-cell dimensions and space-group symmetry. The single-crystal structure refinements (X-ray diffraction data) gave the following structural formulas for the studied samples: Rb 1.80 Na 0.20 Zr[Si 3 O 9 ]·0.4H 2 O for Rb-exchanged hilairite ( R 3, a = 10.477(1), c = 15.377(2) A, R 1( F ) = 3.35% for 2771 reflections with F o > 4σ( F o )), Ba 0.96 H 0.08 Zr[Si 3 O 9 ]·3H 2 O ( R 3, a = 20.976(3), c = 7.857(2) A, R 1( F ) = 4.96% for 4921 reflections with F o > 4σ( F o )) and SrZr[Si 3 O 9 ]·1.5H 2 O ( R 3, a = 20.964(3), c = 7.836(2) A, R 1( F ) = 10.23% for 3598 reflections with F o > 4σ( F o )) for Ba- and Sr-exchanged hilairites, respectively, and Ca 0.83 H 0.34 Zr[Si 3 O 9 ]·3H 2 O ( R 3, a = 10.456(1), c = 7.995(2) A, R 1( F ) = 2.63% for 1477 reflections with F o > 4σ( F o )) and Pb 0.82 Na 0.18 H 0.18 Zr[Si 3 O 9 ]·2.9H 2 O ( R 3, a = 10.477(1), c = 7.994(2) A, R 1( F ) = 2.21% for 1165 reflections with F o > 4σ( F o )) for Ca- and Pb-exchanged hilairites, respectively. All samples were twinned by merohedry and, except the Ca-exchanged sample, also racemically. The results of this study strongly indicate that natural cation-exchange processes can affect hilairite-group minerals under late-hydrothermal conditions.

Two new yttrium silicates have been synthesized by a high-temperature flux-growth technique in air. The phase BaKYSi 2 O 7 is monoclinic, with space group P 2 1 / n , a 9.775(2), b 5.718(1), c 13.096(3) A, β 104.61(3)°, V 708.3(3) A 3 , and Z = 4; Cs 3 YSi 8 O 19 is orthorhombic, space group Pnma , with a 11.476(2), b 7.059(1), c 26.971(5) A, V 2184.9(6) A 3 , and Z = 4. The crystal structures were determined from single-crystal X-ray-diffraction data and refined to R 1( F ) = 2.0% (BaKYSi 2 O 7 ) and R 1( F ) = 2.9% (Cs 3 YSi 8 O 19 ). The phase BaKYSi 2 O 7 represents a novel structure-type, and a compound that may also occur in nature. It has a mixed tetrahedron–octahedron framework structure containing Si 2 O 7 groups and octahedrally coordinated Y atoms ( = 2.256 A). Voids in the framework host [9]-coordinated Ba atoms and [8]-coordinated K atoms. The YO 6 octahedron shares each of its apices with oxygen atoms of the Si 2 O 7 groups. The unusually small Si–O–Si angle of the disilicate group [124.51(9)°] is noteworthy. The diphosphates Na 2 CaP 2 O 7 , M 2 SrP 2 O 7 ( M = K, Rb, Cs) and K 2 CdP 2 O 7 , and the diarsenate K 2 CaAs 2 O 7 , have closely related structures. The phase Cs 3 YSi 8 O 19 is isotypic with isoelectronic Cs 3 ScSi 8 O 19 and the second representative of the microporous framework structure-type MCV–1. The silicate has a mixed octahedron–tetrahedron framework structure with a [ T O 4 ]:[ M O 6 ] ratio of 8:1. The structure contains isolated YO 6 octahedra ( = 2.251 A) sharing corners with SiO 4 tetrahedra to form an open framework with four-, six- and eight-membered rings. Large voids host two fully occupied Cs positions and four partly occupied and disordered Cs positions.

An Al-rich tourmaline from the Sahatany Pegmatite Field at Manjaka, Sahatany Valley, Madagascar, was structurally and chemically characterized. The combination of chemical and structural data yields an optimized formula of X (Na0.53Ca0.09□0.38) Y (Al2.00Li0.90Mn2+0.09Fe2+ 0.01) Z Al6 (BO3)3 T [Si5.61B0.39]O18 V (OH)3 W [(OH)0.6O0.4], with a = 15.777(1), c = 7.086(1) A ( R 1 = 0.017 for 3241 reflections). The 〈 T –O〉 distance of ~ 1.611 A is one of the smallest distances observed in natural tourmalines. The very short 〈 Y –O〉 distance of ~ 1.976 A reflects the relatively high amount of Al at the Y site. Together with other natural and synthetic Al-rich tourmalines, a very good inverse correlation ( r 2 = 0.996) between [4]B and the unit-cell volume was found. [4]B increases with the Al content at the Y site approximately as a power function with a linear term up until [4]B ≈ Si ≈ 3 apfu and Y Al ≈ 3 apfu, respectively, in natural and synthetic Al-rich tourmalines. Short-range order considerations would not allow for [4]B in solid solution between schorl and elbaite, but would in solid solutions between schorl, “oxy-schorl”, elbaite, liddicoatite, or rossmanite and hypothetical [4]B-rich tourmaline end-members with only Al3+ at the Y site. By plotting the [4]B content of synthetic and natural Al-rich tourmalines, which crystallized at elevated PT conditions, it is obvious that there are pronounced correlations between PT conditions and the [4]B content. Towards lower temperatures higher [4]B contents are found in tourmaline, which is consistent with previous investigations on the coordination of B in melts. Above a pressure of ~ 1000–1500 MPa (depending on the temperature) the highest observed [4]B content does not change significantly at a given temperature. The PT conditions of the formation of [4]B-rich olenite from Koralpe, Eastern Alps, Austria, can be estimated as 500–700 MPa/630 °C.

Prismatic colourless crystals of the two novel, isotypic title compounds were obtained by the flux growth technique. The crystal structures have been determined from single-crystal intensity data in space group R 3 with a = 28.819(4) / 28.799(4), c = 13.916(3) / 13.864(3) A, V = 10009(3) / 9958(3) A3, Z = 6, R (F) = 4.99 / 6.44%, respectively. They represent a novel structure type with microporous character. The framework is built from six-membered silicate rings (approximate UDUDUD orientation) containing isolated YO6 octahedra and compressed “six-membered rings”, which in fact build a spiral of corner-sharing SiO4 tetrahedra. Approximately parallel to [111] run two different irregular channels hosting the Rb/Cs and Rb atoms. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Single-crystals of the polar compound magnesium hydrogen vanadate(V), Mg13.4(OH)6(HVO4)2(H0.2VO4)6, were synthesized hydrothermally. It represents the first hydrogen vanadate(V) among inorganic compounds. Its structure was determined by single-crystal X-ray diffraction [space group P 63mc, a = 12.9096(2), c = 5.0755(1) A, V = 732.55(2) A³, Z = 1]. The crystal structure of Mg13.4(OH)6(HVO4)2(H0.2VO4)6 consists of well separated, vacancy-interrupted chains of face sharing Mg2O6 octahedra, with short Mg2—Mg2 distances of 2.537(1) A, embedded in a porous magnesium vanadate 3D framework having the topology of the zeolite cancrinite. All three hydrogen positions in the structure were confirmed by FTIR spectroscopy. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Single crystals of the chabazite-type zeolite mineral willhendersonite, KCaAl 3 Si 3 O 12 ·5H 2 O (from Bellerberg, eastern Eifel district, Germany), were studied by X-ray diffraction methods between 100 and 500 K. The zeolite shows a phase transition from triclinic to rhombohedral symmetry between 350 and 375 K under dry nitrogen and between 450 and 475 K under humid air. Under these conditions, the unit-cell parameters change from P 1 at 350 K [ a , b , c (A); α, β, γ (°); V (A 3 ) = 9.210, 9.210, 9.405; 92.75, 92.80, 90.80; 795.8] to R 3 at 375 K ( a = 9.380 A, α = 91.40°, V = 824.5 A 3 ), and from P 1 at 450 K [ a , b , c (A); α, β, γ (°); V (A 3 ) = 9.215, 9.215, 9.415; 92.65, 92.85, 90.75; 797.5] to R 3 at 475 K ( a = 9.375 A, α = 91.35°, V = 823.8 A 3 ), respectively. The crystal structures were refined based on X-ray diffraction data collected at room temperature [ P 1; a , b , c (A); α, β, γ (°); V (A 3 ) = 9.248(5), 9.259(5), 9.533(5); 92.313(5), 92.761(5), 89.981(5); 814.7(8)], at 373 K [ P 1; a , b , c (A); α, β, γ (°); V (A 3 ) = 9.205(5), 9.231(5), 9.442(5); 92.550(5), 93.086(5), 90.519(5); 800.3(8)], and at 423 K [ R 3, a = 9.411(4) A, α = 91.48(1)°, V = 832.7(6) A 3 ]. Upon heating, the elliptical 8-rings of willhendersonite expand to a triangular shape in the rhombohedral structure with upper and lower rings in the double 6-ring (D6R) twisted by 60° to each other corresponding to the center of symmetry in the center of the D6R. The changes in the framework are accompanied by migration of cations, partly assuming unfavorably low coordinations in the high temperature structure due to the loss of H 2 O molecules. Rehydration at room temperature yields the triclinic structure of willhendersonite, although the single crystals become polysynthetically twinned.

The structure of the mineral parakeldyshite Na1.93ZrSi2O6.93(OH)0.07 is refined by X-ray diffraction analysis. The main crystallographic data are as follows: space group P $$\overline 1 $$ , a = 6.617(2) A, b = 8.813(1) A, c = 5.426(1) A, α = 87.26(3)°, β = 85.68(3)°, γ = 71.45(3)°, and R F = 0.0153. The initial structural model of this mineral is confirmed. Within this model, the structure of parakeldyshite is based on the heteropolyhedral framework formed by [Si2O7] diorthogroups, which are linked together through isolated zirconium octahedra. The fundamental difference between the structure under investigation and the initial structural model is associated with the arrangement of the extraframework cations. A comparative crystal chemical analysis of the zirconium silicates with [Si2O7] diorthogroups is performed.

The crystal structure of a Pb-exchanged form of zorite is studied by X-ray diffraction: Pb3.95(Ca0.1Sr0.05)[Ti(Ti0.80Nb0.20)4Si12O38(OH)] · 9.52H2O (sp. gr. Cmmm, R = 0.0530 for 680 independent reflections). The structure retains the mixed polyhedral framework of zorite, Na6[Ti(Ti,Nb)4(Si6O17)2(O,OH)5] · 11H2O. This framework is composed of xonotlite-like [Si6O17] ribbons linked to each other by columns of vertex-sharing (Ti,Nb)O6 octahedra and isolated TiO5 half-octahedra. Lead atoms in the Pb-exchanged form occupy one site, unlike Cs cations in the Cs-exchanged form of zorite, which are strongly disordered and partially occupy eight positions. The position of Pb2+ cations corresponds to the Na(2) position in the zorite structure, the Sr position in the Sr-exchanged form of ETS-4, and the K position in the K-exchanged form and is similar to the position of the water molecule W(3) in the structure of the Cs-exchanged form of zorite.

The crystal structure of Li3.17(P0.69Ge0.24Mo0.07)O4, which was synthesized by the flux method under the action of an electric field with a potential difference of 0.8 V, was studied by X-ray diffraction on a Nonius Kappa CCD diffractometer (MoKα radiation, λ = 0.71073 A, R = 0.0137). The crystal structure is based on a tetrahedral framework typical of γ-Li3PO4. The framework of the new compound is formed by (P,Ge,Mo)O4 and LiO4 tetrahedra. The positions of additional Li atoms in the structure of Li3.17(P0.69Ge0.24Mo0.07)O4 are found to be different from those in the structure of Li3.31(P0.69Ge0.31)O4, which is synthesized in the absence of an electric field and also belongs to the γ-Li3PO4 structure type.

The crystal structures of K-and Cs-exchanged forms of zorite were studied by X-ray diffraction and IR spectroscopy: K4.75Na1.82[Ti(Ti0.79Nb0.20)4Si12O34(O,OH)5.2] × 10.62 H2O (sp. gr. Cmmm, R= 0.0481 for 516 independent reflections) and Cs4.34Na1.90[Ti(Ti0.80Nb0.18)4Si12O34(O,OH)5] × 5.37 H2O (sp. gr. Cmmm, R = 0.0285 for 621 independent reflections). Both structures retain the mixed polyhedral framework of zorite: Na6Ti(Ti,Nb)4(Si6O17)2(O,OH)5 × nH2O, where n ∼ 11. It is shown that the positions of the atoms located in the cavities of the frameworks of these compounds differ from those in the structures of zorite and its synthetic analogs.

Single crystals of (Ag 3 Hg)VO 4 (I), (Ag 2 Hg 2 ) 3 (VO 4 ) 4 (II), AgHgVO 4 (III), and (Ag2Hg2)2(HgO 2 )(As04)2 (IV) were grown under hydrothermal conditions (250 °C, 5 d) from starting mixtures of elementary mercury, silver nitrate, ammonium vanadate, and disodium hydrogenarsenate, respectively. All crystal structures were determined from X-ray diffraction data, and their chemical compositions were confirmed by electron microprobe analysis. I crystallizes in the tillmannsite structure, whereas II-IV adopt new structure types: (I) I4, Z= 2, a = 7.7095(2) ´ο, c = 4.6714(2) A, 730 structure factors, 24 parameters, R[F 2 > 2σ(F 2 )] = 0.0365; (II) I42d, Z = 4, a = 12.6295(13) A, c = 12.566(3) A, 1524 structure factors, 55 parameters, R[F 2 > 2σ(F 2 )] = 0.0508; (III) C2, Z = 4, a = 9.9407(18) A, b = 5.5730(8) A, c = 7.1210(19) A, β = 94.561(10)°, 1129 structure factors, 48 parameters, R[F 2 > 2σ(F 2 )] = 0.0358; (IV) P31c, Z = 2, a = 6.0261(9) A, c = 21.577(4) A, 1362 structure factors, 52 parameters, R[F 2 > 2σ(F 2 )] = 0.0477. The most striking structural features of I, II, and IV are the formation of tetrahedral cluster cations (Ag 3 Hg) 3 + and (Ag 2 Hg 2 ) 4 + , respectively, built of statistically distributed Ag and Hg atoms with a metal-metal distance of about 2.72 A. The electronic structure of these clusters can formally be considered as two-electron-four-center bonding. The crystal structure of III differs from the protrusive structure types insofar as silver and mercury are located on distinct crystallographic sites without a notable metal-metal interaction >3.55 A. All crystal structures are completed by tetrahedral oxo anions XO 4 3 - (X = V V , As V ) and for IV additionally by a mercurate group, HgO 2 2 - .

The crystal structure of the mineral byelorussite-(Ce) NaMnBa2Ce2Ti2Si8O26(F,OH) · H2O belonging to the joaquinite group was solved and refined to R = 0.033 based on 4813 reflections with I > σ2(I). The parameters of the orthorhombic unit cell are a = 22.301(4) A, b = 10.514(2) A, c = 9.669(2) A, V = 2267.1(8) A3, sp. gr. Ama2, and Z = 4. The structure is composed of three-layer sheets, which consist of dimers of edge-sharing Ti octahedra located between isolated four-membered [Si4O2] rings. The sheets are linked to each other by Mn 5-vertex polyhedra to form a heteropolyhedral framework. Large cavities in the framework are occupied by Na 6-vertex polyhedra, Ba 11-vertex polyhedra, and REE 9-vertex polyhedra.

Single crystals of the title compounds having optical quality and dimensions up to 60 mm have been grown from aqueous solutions. X-ray crystal structure analyses of K2H[N(CH2COO)3] · H2O (I), K2H[N(CH2COO)3] · 2 H2O (II), and Cs2H[N(CH2COO)3] · H2O (III) has been done. Thermal expansion, elastic and thermoelastic properties of the title compounds have been measured employing mechanical and optical dilatometers and ultrasonic resonance techniques, respectively. They possess quite different structural motifs contrary to most other salts having a common anion. An anomalous large molecular volume and a small mean elastic stiffness of K2H[N(CH2COO)3] · 2 H2O is qualitatively interpreted by the small number of Coulomb interactions between the single charged cations and oxygen atoms of the anions. Differences in thermal and elastic properties of corresponding alkali nitrilotriacetates and alkali salts of other large anions are discussed.

During investigations of the system Sc2O3-Al2O3-TiO2-SiO2, a new, unusual microporous compound, Cs3ScSi8O19, was synthesized as colourless plates from a CsF-MoO3 flux. The crystal structure was determined from single-crystal X-ray diffraction data (Mo-Kα radiation, CCD area detector). The compound is orthorhombic, space group Pnma, with a = 11.286(2), b = 7.033(1), c = 26.714(5) Å, and Z = 4 (R1(F) = 2.6% and wR2all(F2) = 7.3%, using 3066 ‘observed’ reflections with Fo > 4σ(Fo)). The crystal structure of Cs3ScSi8O19 represents a new microporous framework structure type (‘MCV-1’), and the compound is exceptional in being the first representative of a mixed octahedral-tetrahedral framework structure, in which the [TO4]:[MO6] ratio is >6:1. The structure is based on isolated, nearly regular ScO6 octahedra [dav(Sc—O) = 2.112 Å] sharing corners with SiO4 tetrahedra to form an open framework with four-, six- and eight-membered rings; the latter are formed by SiO4 tetrahedra only. Two fully occupied Cs positions are located in large framework voids close to the six-membered rings, whereas four partly occupied and disordered Cs positions are close to very large framework voids bordered by the puckered eight-membered rings. The cavities are linked into channels parallel to [100] and [010]. The structure is compared with that of Cs2TiSi6O15 and related microporous scandium-, REE-, titano- and zirconosilicate minerals and compounds. Cs3ScSi8O19 or derivatives may be important in the context of immobilization of radioactive 137Cs waste, cationic conductivity or catalysis.

The crystal structures of six MII guanidinium double sulphates have been determined from single-crystal X-ray diffraction data collected with a CCD area detector at 293 K and were refined. These are the triclinic (space group P-1, Z=1) tetrahydrates [C(NH2)3]2MnII(H2O)4(SO4)2 (a=6.368(1) A, b=6.426(1) A, c=9.952(2) A, α=90.01(1)°, β=97.03(1)°, γ=110.07(1)°, V=379.2(1) A3) and [C(NH2)3]2Cd(H2O)4(SO4)2 (a=6.441(1) A, b=6.459(1) A, c=10.015(2) A, α=90.18(1)°, β=97.02(1)°, γ=110.00(1)°, V=386.3(1) A3), the monoclinic (space group P21/c, Z=2) hexahydrates [C(NH2)3]2FeII(H2O)6(SO4)2 (a=10.011(2) A, b=7.657(2) A, c=12.030(2) A, β=96.85(3)°, V=915.6(3) A3), [C(NH2)3]2Ni(H2O)6(SO4)2 (a=10.026(1) A, b=7.633(1) A, c=12.025(1) A, β=97.09(1)°, V=913.4(1) A3) and [C(NH2)3]2Co(H2O)6(SO4)2 (a=10.079(1) A, b=7.654(1) A, c=12.021(2) A, β=97.02(1)°, V=920.4(2) A3) as well as the triclinic (space group P-1, Z=4) vanadyl compound [C(NH2)3]2VO(H2O)4(SO4)2 (a=7.366(1) A, b=12.366(2) A, c=19.302(4) A, α=107.10(3)°, β=94.07(3)°, γ=90.05(3)°, V=1675.8(5) A3). An investigation of the crystal structures shows layering of the units for all compounds. Three structure types can be distinguished. These types are compared in terms of arrangement and connection of the layers. Comparisons with structurally related compounds are discussed.

During investigations of the system Sc 2 O 3 -Al 2 O 3 -TiO 2- SiO 2 , a new, unusual silicate, K 2 ScFSi 4 O 10 , was synthesised as colourless pseudo-cuboctahedral crystals from a KF-MoO 3 flux. The crystal structure was determined from single-crystal X-ray diffraction data (Mo- Ka radiation, CCD area detector, 2𝛉 max = 65°, R int = 1.07 %) and refined in space group I4/m (no. 87) to R 1( F ) = 1.46% and w R2 all = 4.15% using 976 ‘observed’ reflections with F 0 > 40( F 0 ). Unit-cell parameters are: a = 11.207(2), c = 8.166(2) A, V = 1025.6(4) A 3 , Z = 4. The crystal studied is merohedrally twinned with twin plane {110}, and shows pseudo-symmetry I4/mmm. , The structure contains infinite chains of corner-sharing, nearly regular ScO 4 F 2 octahedra [ d av (Sc-O) = 2.071 A, d av (Sc-F) = 2.042 A] connected via shared F atoms along [001]. These octahedral chains share their O atoms with tubular [001] silicate chains built from four-membered silicate rings. The latter are built from one crystallographically unique, distorted SiO 4 tetrahedron with d av (Si-O) = 1.617 A. The resulting three-dimensional framework hosts voids occupied by a unique, eight-coordinated K atom. K 2 ScFSi 4 O 10 is isotypic with narsarsukite Na 2 (Ti, Fe 3+ )(O, F)Si 4 O 10 , but, although their topologies are basically identical, there exist differences which cause the merohedral twinning and pseudo-holohedry (pseudo- I4/mmm ) of K 2 ScFSi 4 O 10 : the presence of the larger K atom causes a considerable rotation of the octahedral units around [001] and a distinct rearrangement of the framework voids, both leading to the presence of a pseudo-mirror plane {110}. In narsarsukite, no such twinning is possible, as demonstrated by a careful reinvestigation of the crystal structure of a narsarsukite crystal from Mont Saint Hilaire, Canada, which confirmed a previous structure determination. The crystal-chemical relations between K 2 ScFSi 4 O 10 and KTiOPO 4 -type A ScFAsO 4 ( A = Rb, Cs) and other compounds and minerals containing trans or cis MO 4 F 2 ( M = Cr, Al, Fe) octahedra are pointed out. A structure determination of K 2 ScFSi 4 O 10 at 120 K revealed no significant changes of the atomic arrangement. The shrinkage was distinctly stronger along [001] than that along [100].

The crystal structures of eight different L-malates have been determined and refined from single-crystal X-ray diffraction data. The compounds are the monoclinic (space group P21, Z = 2) L-malates Ca(C4H4O5)·3H2O (a = 6.652(1) Å, b = 8.378(1) Å, c = 8.268(1) Å, β = 112.65(2)°, R = 0.027), Ni(C4H4O5)·3H2O (a = 5.762(1) Å, b = 9.006(2) Å, c = 8.406(1) Å, β = 105.54(1)°, R = 0.024), CuH2 (C4H4O5)2 (a = 9.911(1) Å, b = 5.271(1) Å, c = 11.510(1) Å, β = 109.33(1)°, R = 0.031), CsH(C4H4O5)·H2O (a = 7.439(1) Å, b = 7.481(1) Å, c = 7.852(1) Å, β = 116.67(1)°, R = 0.027) as well as the four isomorphic tetragonal (space group P41212, Z = 4) L-malates MgH2 (C4H4O5)2·4H2O (a = 7.524(1) Å, c = 27.459(2) Å, R = 0.041), MnH2 (C4H4O5)2·4H2O (a = 7.548(1) Å, c = 27.707(2) Å, R = 0.027), CoH2 (C4H4O5)2·4H2O (a = 7.519(1) Å, c = 27.537(2) Å, R = 0.030) and ZnH2 (C4H4O5)2·4H2O (a = 7.533(1) Å, c = 27.360(2) Å, R = 0.029). A comparison of the atomic arrangements of L-malates with their racemic counterparts shows different aspects of symmetry as well as differences in the connectivity of the building units. In addition, for all the compounds, powder diffraction data were collected, analysed and submitted to the powder diffraction file (PDF).

Single crystals of bis(guanidinium) tin bis(nitrilotriacetate) hydrate (GuSN) and bis(methylammonium) tin bis(nitrilotriacetate) dihydrate (MetamSN) having optical quality and dimensions up to 15 × 15 × 20 mm were grown from aqueous solutions. The isotypy with the corresponding zirconium and hafnium compounds (GuZN, GuHN, and MetamZN, respectively)) was proved by X-ray structure analyses (GuSN: space group Ccc21, a 1 = 11.338 Å, a 2 = 20.285 Å, a 3 = 10.178 Å, Z = 4, density 1.796 g cm-3; MetamSN: space group P212121, a 1 = 9.851 Å, a 2 = 14.164 Å, a 3 = 15.548 Å, Z = 4, density 1.821 g cm-3). Distinct differences in the dimensions of the tin bis(nitrilotriacetate) and zirconium bis(nitrilotriacetate) anions could be derived from structural features. The molecular volume of the latter is about 6 Å3 larger than that of the tin complex. Along one direction perpendicular to the twofold or quasi-twofold axis the diameter of the tin complex is about 0.18 Å shorter. Thermal expansion, dielectric, piezoelectric, elastic, thermoelastic and piezo elastic properties of corresponding tin, zirconium and hafnium compounds are quite similar. The small differences in the dimensions of the anions, however, are clearly reflected in the elastic longitudinal stiffnesses. The earlier described phase transitions in GuZN exist also in GuSN as confirmed by X-ray analysis at 100 K. The temperature of the transition region II is shifted to lower temperatures by about 4 and 6 K, if Zr is substituted by Sn and Hf, respectively. All anomalous phenomena observed during the transition in GuZN and GuHN are also found in GuSN.

Li3Sc(MoO4)3, trilithium scandium trimolybdate(VI), is isotypic with its FeIII analogue and a number of Li3MIII(MoO4)3 and Li2MII2(MoO4)3 compounds. It contains three substitutionally disordered (Li,Sc) sites; two of these show octahedral coordination and contain about 42 and 25% Sc, whereas the third site has a trigonal-prismatic environment and contains only about 8% Sc. The average (Li,Sc)—O bond lengths are 2.092, 2.129, and 2.195 A, respectively. The (Li,Sc)O6 polyhedra share either faces or edges with equivalent polyhedra to form columns and zigzag chains, all running parallel to [100]. These building units are connected, via two non-equivalent MoO4 tetrahedra (average Mo—O bond length 1.771 A), into a three-dimensional framework.

Bi3ScMo2O12, tribismuth(III) scandium molybdate(VI), has a framework structure derived from that of scheelite. It is nearly isotypic with Bi3FeMo2O12; while in the latter the FeIII atom is tetrahedrally coordinated by O atoms, the Sc atom in the title compound has a distorted octahedral coordination, and is substituted by Bi to a very minor extent (ca 4%). The change in coordination is achieved predominantly by shifts of two O atoms. The average Sc—O and Mo—O bond lengths are 2.162 and 1.775 A, respectively. The environments of the two eight-coordinated Bi sites are very similar to those in Bi3FeMo2O12. All atoms are on general positions except Sc and one Bi (both of which have site symmetry 2).

Discandium(III) titanate(IV), Sc2TiO5, prepared by the flux method, has a pseudobrookite-type structure. The Sc and Ti atoms are partially disordered on the two octahedrally coordinated metal (M) sites (Wyckoff designations 8f and 4c in space group Cmcm). The most probable cation distribution suggests the approximate structural formula [8f](Sc0.6,Ti0.4)2[4c](Sc0.8Ti0.2)O5, in agreement with earlier observations of a preference of Ti for the more distorted 8f site in isotypic AIII2BIVO5 compounds. The average M—O bond lengths for the 8f and 4c sites are 2.059 and 2.095 A, respectively. The strongly distorted octahedra share edges to form trioctahedral units, which are linked into infinite double chains along c. Further sharing of octahedral edges results in a three-dimensional framework. All atoms are on special positions. An Al-bearing variety of Sc2TiO5 has Al preferentially incorporated on the 4c site.