ORCID Profile
0000-0003-2025-6460
Current Organisation
University of Innsbruck, Faculty of Geo- and Atmospheric Sciences
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Publisher: Schweizerbart
Date: 25-05-2016
Publisher: Mineralogical Association of Canada
Date: 26-05-2021
Abstract: The crystal structure of arctite, (Na5Ca)Ca6Ba(PO4)6F3 (Rm, a = 7.904 Å, с = 41.320 Å), was refined in 1984 by E. Sokolova. According to modern concepts, this mineral belongs to the intercalated antiperovskites and is characterized by intercalation of triple antiperovskite layers {[F3(Ca7Na5)](PO4)4}4+ and tetrahedral layers Ba(PO4)24–. The pyrometamorphic rocks of the Hatrurim Complex, which are distributed along the Dead Sea Rift, are the origin of eight new minerals with intercalated antiperovskite structures, all discovered within the last five years. Therefore, an update and improvement of the classification and nomenclature was required. The new classification of the arctite supergroup was approved by the CNMNC IMA (Memorandum 95–SM20). The arctite supergroup combines the arctite group (minerals with triple antiperovskite layers), which includes arctite, (Na5Ca)Ca6Ba(PO4)6F3 nabimusaite, KCa12(SiO4)4(SO4)2O2F dargaite, BaCa12(SiO4)4(SO4)2O3 and ariegilatite, BaCa12(SiO4)4(PO4)2F2O, with the zadovite group (minerals with single antiperovskite layers), which includes zadovite, BaCa6[(SiO4)(PO4)](PO4)2F aradite, BaCa6[(SiO4)(VO4)](VO4)2F gazeevite, BaCa6(SiO4)2(SO4)2O and stracherite, BaCa6(SiO4)2[(PO4)(CO3)]F. Another ungrouped member of the arctite supergroup is aravaite, Ba2Ca18(SiO4)6[(PO4)3(CO3)]F3O – a unique mineral which is formed by the ordered intercalation of super-modules of ariegilatite and stracherite. In addition, a description of aravaite as a new mineral is presented in this paper. The crystal structure has been previously published (Krüger et al. 2018). Furthermore, preliminary data for potentially new minerals of the arctite supergroup, found in rocks of the Hatrurim Complex, are discussed.
Publisher: International Union of Crystallography (IUCr)
Date: 14-03-2013
DOI: 10.1107/S0108270113006069
Abstract: Crystals of KAlSiO 4 - O1 (potassium aluminium silicate) were synthesized using a flux method and analysed utilizing single-crystal X-ray diffraction and electron microprobe analysis. Both methods confirm that the crystals are nonstoichiometric according to K 1− x Al 1− x Si 1+ x O 4 with x = 0.04 (1). KAlSiO 4 - O1 is closely related to the stuffed derivatives of tridymite, although the topology of the Si/Al-ordered framework is different. Six-membered rings of UUDDUD and UUUDDD (U = up and D = down ratio 2:1) configurations are present in layers parallel to the ab plane. In contrast, the framework of tridymite exhibits UDUDUD rings. The crystals are affected by inversion, pseudo-orthorhombic and pseudo-hexagonal twinning.
Publisher: Copernicus GmbH
Date: 02-07-2021
Abstract: Abstract. Kahlenbergite, ideally KAl11O17, and Fe-rich hibonite, CaAl10Fe2O19, are high-temperature minerals found in “olive” subunits of pyrometamorphic rocks, in the Hatrurim Basin, the Negev desert, Israel. The crystal structures of both minerals are refined using synchrotron radiation single-crystal diffraction data. The structure of kahlenbergite (P63/mmc a=5.6486(1) Å b=22.8970(3) Å Z=2) exhibits triple spinel blocks and so-called R blocks. The spinel blocks show mixed layers with AlO6 octahedra and (Al0.56Fe0.44)O4 tetrahedra and kagome layers with (Al0.92Fe0.08)O6 octahedra. One-dimensional diffuse scattering observed parallel to c* implies stacking faults in the structure. Also, in one of the investigated kahlenbergite crystals additional reflections can be identified, which obviously belong to a second phase with a smaller lattice parameter c: Fe3+-rich hibonite. The structure of hibonite contains the same spinel blocks as kahlenbergite. The R blocks in hibonite contain Ca atoms, AlO5 bipyramids, and AlO6 octahedra, whereas the R blocks in kahlenbergite contain potassium atoms and AlO4 tetrahedra.
Publisher: MDPI AG
Date: 08-03-2018
DOI: 10.3390/MIN8030109
Abstract: Ariegilatite, BaCa12(SiO4)4(PO4)2F2O (R 3 ¯ m, a = 7.1551(6) Å, c = 41.303(3) Å, V = 1831.2(3) Å3, Z = 3), is a new member of the nabimusaite group exhibiting a modular intercalated antiperovskite structure derived from hatrurite. It was found in a few outcrops of pyrometamorphic rocks of the Hatrurim Complex located in the territories of Israel, Palestine and Jordan. The holotype specimen is an altered spurrite marble from the Negev Desert near Arad city, Israel. Ariegilatite is associated with spurrite, calcite, brownmillerite, shulamitite, CO3-bearing fluorapatite, fluormayenite-fluorkyuygenite and a potentially new mineral, Ba2Ca18(SiO4)6(PO4)3(CO3)F3O. Ariegilatite is overgrown and partially replaced by stracherite, BaCa6(SiO4)2[(PO4)(CO3)]F. The mineral forms flat disc-shaped crystals up to 0.5 mm in size. It is colorless, transparent, with white steaks and vitreous luster. Optically, ariegilatite is uniaxial, negative: ω = 1.650(2), ε = 1.647(2) (λ = 589 nm). The mean composition of the holotype ariegilatite, (Ba0.98K0.01Na0.01)Σ1(Ca11.77Na0.08Fe2+0.06Mn2+0.05Mg0.04)Σ12(Si3.95Al0.03Ti0.02)Σ4(P1.70C0.16Si0.10S6+0.03V0.01)Σ2F2.04O0.96, is close to the end-member formula. The structure of ariegilatite is described as a stacking of the two modules {F2OCa12(SiO4)4}4+ and {Ba(PO4)2}4− along (001). Ariegilatite, as well as associated stracherite, are high-temperature alteration products of minerals of an early clinker-like association. These alterations took place under the influence of pyrometamorphism by-products, such as gases and fluids generated by closely-spaced combustion foci.
Publisher: Mineralogical Society of America
Date: 10-2018
DOI: 10.2138/AM-2018-6493
Publisher: Mineralogical Society
Date: 31-07-2023
DOI: 10.1180/MGM.2023.57
Publisher: Mineralogical Society
Date: 24-07-2023
DOI: 10.1180/MGM.2023.56
Publisher: International Union of Crystallography (IUCr)
Date: 28-08-2009
DOI: 10.1107/S0108768109026974
Abstract: The crystal structure of Sr 10 Ga 6 O 19 was investigated by in situ single-crystal X-ray diffraction in the temperature range 298–673 K. At ambient conditions the compound shows a (3 + 1)-dimensional modulated structure in the superspace group C 2/ c (0β0) s 0 [ a = 34.9145 (13), b = 7.9369 (2), c = 15.9150 (7) Å and β = 103.551 (3)°] with a modulation wavevector of q = 0.4288 (2) b *. Whereas the presented structural model uses first-order harmonic modulation functions only, some features of the modulations are discussed utilizing an electron density derived by the maximum entropy method. Furthermore, two phase transitions were identified: between 453 and 503 K the incommensurate superstructure is replaced by a doubling of the a and b lattice constants, and between 503 and 673 K a phase with the basic cell is formed, identical to α-Sr 10 Ga 6 O 19 . Under some cooling conditions crystals showing a combined diffraction pattern of both superstructures can be obtained. The relation of these results to α-Sr 10 Ga 6 O 19 [Kahlenberg (2001). J. Solid State Chem. 160 , 421–429] is discussed.
Publisher: International Union of Crystallography (IUCr)
Date: 12-2018
DOI: 10.1107/S2052520618012271
Abstract: The crystal structure of the new mineral aravaite Ba 2 Ca 18 (SiO 4 ) 6 (PO 4 ) 3 (CO 3 )F 3 O [R{\\bar 3}m, a = 7.12550 (11), c = 66.2902 (13) Å, V = 2914.81 (8) Å 3 , Z = 3] was solved from single-crystal diffraction data, collected using synchrotron radiation at the X06DA beamline of the Swiss Light Source. The unit cell of this modular mineral contains six layers of {Ba(PO 4 ) 1.5 (CO 3 ) 0.5 } 3.5− (T-layer), three triple antiperovskite layers (tAP) {(F 2 OCa 12 )(SiO 4 ) 4 } 4+ , and three single antiperovskite layers (sAP) {(FCa 6 )(SiO 4 ) 2 } 3+ . The structure refinement confirms a model with a layer sequence of T–sAP–T–tAP as an average structure of this mineral. However, one-dimensional diffuse scattering observed parallel to c * implies imperfections in the stacking sequence of the average structure. Qualitative modelling of disorder confirms that the alternating sequence of T–sAP and T–tAP blocks is disturbed. The blocks occurring in this new mineral are known from other so-called hexagonal intercalated antiperovskite structures: T–sAP (stracherite and zadovite group), T–tAP (ariegilatite and nabimusaite group).
Publisher: International Union of Crystallography (IUCr)
Date: 10-07-2008
DOI: 10.1107/S0108768108016029
Abstract: A high-temperature X-ray diffraction study revealed that brownmillerite-type Ca 2 Al 2 O 5 transforms to an incommensurately modulated structure at elevated temperatures. Single crystals of Ca 2 Al 2 O 5 were synthesized in an end-loaded piston cylinder press at 2.5 GPa and 1273 K. The diffraction pattern observed at 1090 (10) K by in situ single-crystal diffraction experiments can be indexed by an I -centred orthorhombic cell and a modulation wavevector of q = 0.595 (1) c * . A (3 + 1)-dimensional model in superspace group Imma (00γ) s 00 was used to refine the modulated structure. The structure is assembled from two building units: (i) layers of corner-sharing [AlO 6 ] octahedra, stacked along b alternate with (ii) layers of zweier single chains of [AlO 4 ] tetrahedra running along a . The modulated structure arises from an aperiodic sequence of two different configurations of the chains within the tetrahedral layers. The modulated high-temperature phase of Ca 2 Al 2 O 5 is isotypic to the modulated high-temperature modification of Ca 2 Fe 2 O 5 . A large hysteresis was found in the phase-transition temperature. On heating, the transition occurs at ca 1075 (10) K on cooling, satellite reflections can be observed down to 975 (10) K. The characterization of Ca 2 Al 2 O 5 is completed by Raman spectroscopy, including a partial interpretation of the spectra.
Publisher: MDPI AG
Date: 30-12-2019
DOI: 10.3390/MIN10010038
Abstract: The crystal structure of bentorite, ideally Ca6Cr2(SO4)3(OH)12·26H2O, a Cr3+ analogue of ettringite, is for the first time investigated using X-ray single crystal diffraction. Bentorite crystals of suitable quality were found in the Arad Stone Quarry within the pyrometamorphic rock of the Hatrurim Complex (Mottled Zone). The preliminary semi-quantitative data on the bentorite composition obtained by SEM-EDS show that the average Cr/(Cr + Al) ratio of this s le is .8. Bentorite crystallizes in space group P31c, with a = b = 11.1927(5) Å, c =21.7121(10) Å, V = 2355.60(18) Å3, and Z = 2. The crystal structure is refined, including the hydrogen atom positions, to an agreement index R1 = 3.88%. The bentorite crystal chemical formula is Ca6(Cr1.613Al0.387)Σ2[(SO4)2.750(CO3)0.499]Σ3.249(OH)11.502·~25.75H2O. The Raman spectra of bentorite from two different localities exhibit the presence of the main stretching and bending vibrations related to the sulfate group at 983 cm−1 (ν1), 1109 cm−1 (ν3), 442 cm−1 (ν2), and 601 cm−1 (ν4). Moreover, the presence of bands assigned to the symmetric Cr(OH)63− stretching mode and hydroxyl deformation vibrations of Cr–OH units at ~540 cm−1 and ~757 cm−1, respectively, may be used to distinguish between ettringite and bentorite. In situ high temperature single crystal XRD experiments show that the decomposition of bentorite starts at ca. 45 °C and that a dehydroxylation product similar to metaettringite is formed.
Publisher: Mineralogical Society
Date: 14-06-2019
DOI: 10.1180/MGM.2019.37
Abstract: Levantite, with the end-member formula KCa 3 (Al 2 Si 3 )O 11 (PO 4 ), is the phosphate analogue of latiumite, KCa 3 (Al 3 Si 2 )O 11 (SO 4 , CO 3 ) found in gehlenite–wollastonite hornfels on Har Parsa, Negev Desert, Israel. Levantite forms later zones on long-prismatic crystals of latiumite. Rarer homogeneous colourless levantite crystals up to 0.2 mm long and with mean composition (K 0.94 Ba 0.01 Na 0.01 □ 0.04 ) Σ1.00 (Ca 2.96 Mg 0.03 ) Σ2.99 {(Si 2.69 Al 2.06 Fe 3+ 0.16 P 0.06 ) Σ4.97 O 11 }[(PO 4 ) 0.65 (SO 4 ) 0.35 ] Σ1.00 were noted. Minerals of the levantite–latiumite series are associated with gehlenite, wollastonite, clinopyroxene of the esseneite–diopside series, anorthite and Ti-bearing andradite. Levantite crystalises in space group P 2 1 with unit-cell parameters a = 12.1006(9) Å, b = 5.1103(4) Å, c = 10.8252(9) Å, β = 107.237(8)°, V = 639.34(9) Å 3 and Z = 2. The structure of levantite is analogous to latiumite. It is formed by tetrahedral hybrid zweier double layers [(Si,Al) 10 O 22 ] connected by Ca atoms. Three Ca atoms linked to different double layers are bridged over by (PO 4 ) and minor (SO 4 ) groups. K atoms reside in the cavities between two superimposed zweier double layers. The measured micro-indentation hardness of levantite gave VHN 50 = 580(19) (mean of 14), range 550–611 kg/mm 2 , which correlates with 5 on the Mohs scale. Cleavage is good on (100). Twinning on (100) is polysynthetic or simple. The calculated density is 2.957 g cm –3 . Levantite is optically negative with α = 1.608(2), β = 1.618(2), γ = 1.622(2) (λ = 589 nm), 2V meas. = 70(5)° and 2V calc. = 64.3°. Dispersion of the optical axes r v is weak the optical orientation is: Z = b , X ^ c = 22–27° and it is non-pleochroic. Minerals of the levantite–latiumite series from Israel show characteristic Raman spectra with the main bands at 994 cm –1 [ν 1 (SO 4 ) 2– ] and 945 cm –1 [ν 1 (PO 4 ) 3– ]. The band intensity ν 1 (PO 4 ) 3– /ν 1 (SO 4 ) ratio is well correlated with P and S contents in the investigated minerals. The strongest lines in the powder diffraction pattern [ d obs , Å ( I , %) ( hkl )] are: 3.0762(100)(310), 2.8551(96)( $\\bar 2$ 13), 2.9704(92)( $\\bar 3$ 12), 2.8573(83)(013), 2.5552(66)(020), 2.8228(48)(212), 2.8893(40)(400), and 3.0634(30)(103).
Publisher: American Chemical Society (ACS)
Date: 02-2013
DOI: 10.1021/CM3038476
Publisher: MDPI AG
Date: 21-07-2018
DOI: 10.3390/MIN8070308
Abstract: The new mineral sharyginite, Ca3TiFe2O8 (P21ma, Z = 2, a = 5.423(2) Å, b = 11.150(8) Å, c = 5.528(2) Å, V = 334.3(3) Å3), a member of the anion deficient perovskite group, was discovered in metacarbonate xenoliths in alkali basalt from the Caspar quarry, Bellerberg volcano, Eifel, Germany. In the holotype specimen, sharyginite is widespread in the contact zone of xenolith with alkali basalt. Sharyginite is associated with fluorellestadite, cuspidine, brownmillerite, rondorfite, larnite and minerals of the chlormayenite-wadalite series. The mineral usually forms flat crystals up to 100 µm in length, which are formed by pinacoids {100}, {010} and {001}. Crystals are flattened on (010). Sharyginite is dark brown, opaque with a brown streak and has a sub-metallic lustre. In reflected light, it is light grey and exhibits rare yellowish-brown internal reflections. The calculated density of sharyginite is 3.943 g·cm-3. The empirical formula calculated on the basis of 8 O apfu is Ca3.00(Fe3+1.00Ti4+0.86Mn4+0.11Zr0.01Cr3+0.01Mg0.01)Σ2(Fe3+0.76Al0.20Si0.04)Σ1.00O8. The crystal structure of sharyginite, closely related to shulamitite Ca3TiFeAlO8 structure, consists of double layers of corner-sharing (Ti, Fe3+) O6 octahedra, which are separated by single layers of (Fe3+O4) tetrahedra. We suggest that sharyginite formed after perovskite at high-temperature conditions °C.
Publisher: Mineralogical Society of America
Date: 03-2020
DOI: 10.2138/AM-2020-7208
Abstract: A new mineral, siwaqaite, ideally Ca6Al2(CrO4)3(OH)12·26H2O [P31c, Z = 2, a = 11.3640(2) Å, c = 21.4485(2) Å, V = 2398.78(9) Å3], a member of the ettringite group, was discovered in thin veins and small cavities within the spurrite marble at the North Siwaqa complex, Lisdan-Siwaqa Fault, Hashem region, Jordan. This complex belongs to the widespread pyrometamorphic rock of the Hatrurim Complex. The spurrite marble is mainly composed of calcite, fluorapatite, and brownmillerite. Siwaqaite occurs with calcite and minerals of the baryte-hashemite series. It forms hexagonal prismatic crystals up to 250 μm in size, but most common are grain aggregates. Siwaqaite exhibits a canary yellow color and a yellowish-gray streak. The mineral is transparent and has a vitreous luster. It shows perfect cleavage on (1010). Parting or twinning is not observed. The calculated density of siwaqaite is 1.819 g/cm3. Siwaqaite is optically uniaxial (–) with ω = 1.512(2), ε = 1.502(2) (589 nm), and non-pleochroic. The empirical formula of the holotype siwaqaite calculated on the basis of 8 framework cations and 26 water molecules is Ca6.01(Al1.87Si0.12)Σ1.99[(CrO4)1.71(SO4)1.13(SeO4)0.40]Σ3.24(OH)11.63·26H2O. X-ray diffraction (XRD), Raman, and infrared spectroscopy confirm the presence of OH- groups and H2O molecules and absence of (CO3)2– groups. The crystal structure of this Cr6+-analog of ettringite was solved by direct methods using single-crystal synchrotron XRD data. The structure was refined to an agreement index R1 = 4.54%. The crystal structure of siwaqaite consists of {Ca6[Al(OH)6]2·24H2O}6+ columns with the inter-column space (channels) occupied by (CrO4)2–, (SO4)2–, (SeO4)2–, and (SO3)2– groups and H2O molecules. The tetrahedrally coordinated site occupied by different anion groups is subjected to disordering and rotation of these tetrahedra within the structure. The temperature of siwaqaite formation is not higher than~70–80 °C, as is evident from the mineral association and as inferred from the formation conditions of the natural and synthetic members of the ettringite group minerals, which are stable at conditions of T & 120 °C and pH = 9.5–13. The name siwaqaite is derived from the name of the holotype locality—Siwaqa area, where the mineral was found.
Publisher: International Union of Crystallography (IUCr)
Date: 29-08-2010
Publisher: MDPI AG
Date: 10-09-2018
DOI: 10.3390/MIN8090399
Abstract: Rusinovite, Ca10(Si2O7)3Cl2, was found at two new localities, including Shadil-Khokh volcano, South Ossetia and Bellerberg volcano, Caspar quarry, Germany. At both of these localities, rusinovite occurs in altered carbonate-silicate xenoliths embedded in volcanic rocks. The occurrence of this mineral is connected to specific zones of the xenolith characterized by a defined Ca:Si 2 ratio. Chemical compositions, as well as the Raman spectra of the investigated rusinovite s les, correspond to the data from the locality of rusinovite holotype—Upper Chegem Caldera, Northern Caucasus, Russia. The most intense bands of the Raman spectra are related to vibrations of (Si2O7) groups. Unit cell parameters of rusinovite from South Ossetia are: a = 3.76330(4) Å, b = 16.9423(3) Å, c = 17.3325(2) Å, V = 1105.10(4) Å3, Z = 2. The performed synchrotron radiation diffraction experiments did not confirm a doubling of c as reported for the synthetic phase, Ca10(Si2O7)3Cl2. However, one-dimensional diffuse scattering parallel to b* has been observed. This can be interpreted with an ordered arrangement of Si2O7 groups creating layers with a doubled a parameter. Consequently, the two different displacements of neighbouring layers allow random stacking faults to occur.
Publisher: Wiley
Date: 03-09-2018
DOI: 10.1111/JACE.16001
Location: Serbia
Location: Austria
No related grants have been discovered for Biljana Krüger.