No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
The crystal structure of natural gugiaite, Ca2BeSi2O7
Abstract
The crystal structure of the original natural gugiaite, Ca2BeSi2O7, from the skarn rocks in the Gugia alkaline complex, Liaoning Province, China, is determined from CCD data in space group P (4) over bar2(1)m, n = 7.4330(10), c = 4.9970(10) Angstrom, V = 276.08(8) Angstrom (3), Z = 2. The structure is basically consistent with that of the synthetic one, although there are longer Be-O distances, smaller distortions of BeO4 tetrahedron and larger distortions of SiO4 tetrahedron than those in synthetic one.
... Bensch and Schur (1995); (18) Lin et al. (1992), Giester and Rieck (1994), Knight et al. (2010);(19) Pabst (1943), Hazen and Finger (1983); (20) Giester and Rieck (1996);(21) Uvarova et al. (2004a);(22) Szymański et al. (1982); (23) Livingstone et al. (1976); (24) Perrault and Szymański (1982);(25) Kabalov et al. (1998); (26) Yang et al. (2011);(27) Takeuchi et al. (1969), Kato and Takéuchi (1983); (28) Kato and Watanabe (1992); (29) Ozawa et al. (1983); (30) Ozawa et al. (1983); (31) Dunn and Peacor (1984); (32) Kasahev and Sapozhnikov (1978);(33) Fleet (1965); (34) Gebert et al. (1983), Lazebnik et al. (1984);(35) Es'kova et al. (1974), Shumyatsaya et al. (1980);(36) Cámara et al. (2006); (37) Alberti and Galli (1983); (38) Merlino (1983); (39) Uvarova et al. (2004b); (40) Grice and Gault (1995);(41) Heinrich et al. (1994); (42) Yamnova et al. (1996);(43) Krivovichev et al. (2007). Piergorite-(Ce) [(4.5.8)2(4.5 2 .8)2(5 3 )6(5 2 .8)4( 5 4 ) Quint (1987); (2) Papike and Zoltai (1967), Baur et al. (1990); (3) Ghose and Wan (1976); (4) Kimata (1981); (5) Louisnathan (1970), Wiedenmann et al. (2009);(6) Dondi et al. (1999); (7) Louisnathan (1971), Kimata and Li (1982); (8) Kimata and Ohashi (1982), Yang et al. (2001); (9) Louisnathan (1969), Bindi et al. (2001); (10) Matsubara et al. (1998); (11) Cannillo et al. (1967Cannillo et al. ( , 1992, Grice and Hawthorne (1989);(12) Dal Negro et al. (1967), Grice and Hawthorne (2002); (13) Grice and Robinson (1984); (14) Della ; (15) Oberti et al. (1999); (16) , Miyawaki et al. (2015); (17) Bakakin et al. (1970), Pekov et al. (1998Pekov et al. ( , 2001, Pushcharovskii et al. (1999); (20) Pekov et al. (1998), Pushcharovskii et al. (1999); (21) Mazzi et al. (1979); (22) (2014); (2) Pluth and Smith (2002); (3) Yakovenchuk et al. (2007); (4) Eggleton (1972), Eggleton and Chappell (1978), Guggenheim and Eggleton (1994); (5) ...
The structure hierarchy hypothesis states that structures may be ordered hierarchically according to the polymerisation of coordination polyhedra of higher bond-valence. A hierarchical structural classification is developed for sheet-silicate minerals based on the connect-edness of the two-dimensional polymerisations of (TO 4) tetrahedra, where T = Si 4+ plus As 5+ , Al 3+ , Fe 3+ , B 3+ , Be 2+ , Zn 2+ and Mg 2+. Two-dimensional nets and oikodoméic operations are used to generate the silicate (sensu lato) structural units of single-layer, double-layer and higher-layer sheet-silicate minerals, and the interstitial complexes (cation identity, coordination number and ligancy, and the types and amounts of interstitial (H 2 O) groups) are recorded. Key aspects of the silicate structural unit include: (1) the type of plane net on which the sheet (or parent sheet) is based; (2) the u (up) and d (down) directions of the constituent tetrahedra relative to the plane of the sheet; (3) the planar or folded nature of the sheet; (4) the layer multiplicity of the sheet (single, double or higher); and (5) the details of the oikodoméic operations for multiple-layer sheets. Simple 3-connected plane nets (such as 6 3 , 4.8 2 and 4.6.12) have the stoichiometry (T 2 O 5) n (Si:O = 1:2.5) and are the basis of most of the common rock-forming sheet-silicate minerals as well as many less-common species. Oikodoméic operations, e.g. insertion of 2-or 4-connected vertices into 3-connected plane nets, formation of double-layer sheet-structures by (topological) reflection or rotation operations, affect the connectedness of the resulting sheets and lead to both positive and negative deviations from Si:O = 1:2.5 stoichiometry. Following description of the structural units in all sheet-silicate minerals, the minerals are arranged into decreasing Si:O ratio from 3.0 to 2.0, an arrangement that reflects their increasing structural connectivity. Considering the silicate component of minerals, the range of composition of the sheet silicates completely overlaps the compositional ranges of framework silicates and most of the chain-ribbon-tube silicates.
... References: (1)Quint (1987); (2)Papike and Zoltai (1967),Baur et al. (1990);(3) Ghose and Wan (1976); (4)Kimata (1981); (5)Louisnathan (1970),Wiedenmann et al. (2009); (6)Dondi et al. (1999); (7)Louisnathan (1971),Kimata and Li (1982); (8)Kimata and Ohashi (1982),Yang et al. (2001); (9)Louisnathan (1969),Bindi et al. (2001); (10)Matsubara et al. (1998);(11) Cannillo et al. (1967(11) Cannillo et al. ( , 1992,Grice and Hawthorne (1989);(12)Dal Negro et al. (1967), Grice and Hawthorne (2002); (13) Grice and Robinson (1984); (14) Della Ventura et al. (2002), Oberti et al. (2018); (15) Oberti et al. (1999), Oberti et al. (2018); (16) Mellini and Merlino (1977), Miyawaki et al. (2015); (17) Hawthorne et al. (1998); (18) Boiocchi et al. (2006); (19)Bakakin et al. (1970),Pekov et al. (1998Pekov et al. ( , 2001,Pushcharovskii et al. (1999); (20)Pekov et al. (1998),Pushcharovskii et al. (1999);(21)Mazzi et al. (1979); (22) Hesse and Stümpel (1986); (23) Danisi et al. (2015); (24) Huminicki and Hawthorne (2002b); (25) Grice et al. (2009); (26) Chakhmouradian et al. (2014); (27) Rouse et al. (1994); and (28) Garcés et al. (1988). *P = planar; 1F = folded in one direction. ...
The structure hierarchy hypothesis states that structures may be ordered hierarchically according to the polymerisation of coordination polyhedra of higher bond-valence. A hierarchical structural classification is developed for sheet-silicate minerals based on the connect-edness of the two-dimensional polymerisations of (TO 4) tetrahedra, where T = Si 4+ plus As 5+ , Al 3+ , Fe 3+ , B 3+ , Be 2+ , Zn 2+ and Mg 2+. Two-dimensional nets and oikodoméic operations are used to generate the silicate (sensu lato) structural units of single-layer, double-layer and higher-layer sheet-silicate minerals, and the interstitial complexes (cation identity, coordination number and ligancy, and the types and amounts of interstitial (H 2 O) groups) are recorded. Key aspects of the silicate structural unit include: (1) the type of plane net on which the sheet (or parent sheet) is based; (2) the u (up) and d (down) directions of the constituent tetrahedra relative to the plane of the sheet; (3) the planar or folded nature of the sheet; (4) the layer multiplicity of the sheet (single, double or higher); and (5) the details of the oikodoméic operations for multiple-layer sheets. Simple 3-connected plane nets (such as 6 3 , 4.8 2 and 4.6.12) have the stoichiometry (T 2 O 5) n (Si:O = 1:2.5) and are the basis of most of the common rock-forming sheet-silicate minerals as well as many less-common species. Oikodoméic operations, e.g. insertion of 2-or 4-connected vertices into 3-connected plane nets, formation of double-layer sheet-structures by (topological) reflection or rotation operations, affect the connectedness of the resulting sheets and lead to both positive and negative deviations from Si:O = 1:2.5 stoichiometry. Following description of the structural units in all sheet-silicate minerals, the minerals are arranged into decreasing Si:O ratio from 3.0 to 2.0, an arrangement that reflects their increasing structural connectivity. Considering the silicate component of minerals, the range of composition of the sheet silicates completely overlaps the compositional ranges of framework silicates and most of the chain-ribbon-tube silicates.
... The three parameters (T/X, r 2 T2, ,T1-O3-T2.8), for the three structures, hydroxylgugiaite (0.65, 26, 120) (this publication), natural gugiaite (0.65, 41, 120) (Yang et al. 2001), and synthetic gugiaite (0.64, 44, 128) (Kimata & Ohashi 1982), are all very similar and indicative of a commensurately unmodulated crystal structure. ...
Hydroxylgugiaite, ideally (Ca3A1)R4(Si3.5Be2.5)R6O11(OH)3, is a new mineral species from two localities in the Larvik plutonic complex in Porsgrunn, Telemark, Norway, and one locality in Iĺimaussaq, Greenland. Hydroxylgugiaite crystals occur as squat dipyramids {111} (30 × 50 μm) or as elongate tetragonal prisms. The crystals are translucent, white to pale grey in color, with a white streak and vitreous luster. It is brittle, with no apparent cleavage. Hydroxylgugiaite is uniaxial positive with ω = 1.622 ± 0.002 and ϵ = 1.632 ± 0.002. There is no pleochroism and birefringence is low. The average of eight analyses of a single grain of type material (oxide wt.%) gave Na2O 2.04, CaO 32.90, FeO 0.22, MnO 0.74, BeO 13.47 (LA-ICP-MS), Al2O3 0.74, SiO2 44.06, F 1.74, H2O (assuming 3 OH + F) 4.93, Total (-0.73 O = F) 100.10. Potassium, strontium, and magnesium were measured but not detected. The calculated density is 2.79 g cm-3. The empirical formula on the basis of 14 anions including 3 OH- + F- is: (Ca2.76Na0.31Mn0.05Fe0.01)R3.13(Si3.45Be2.53Al0.07)R6.05O11[(OH)2.57F0.43]R3. The formula from crystal-structure analysis of the Saga specimen is: (Ca3.02A0.98)R4(Si1.79Be0.21)R2(Be2.29Si1.71)R4O11(OH)3. Combined structural and chemical data gives the fol lowing formula for the Nakkaalaaq specimen: (Ca2.88A0.98Na0.12Mn0.02)R4(Si1.80Be0.17Al0.03)R2 (Be2.32Si1.68)R4O11[(OH)2.70F0.30]R3; with simplified formula (Ca,A)4(Si,Be)2(Be,Si)4O11(OH)3. The crystal structure of hydroxylgugiaite is tetragonal in acentric space group P421/m, with a 7.4151(2), b 7.4151, c 4.9652(1) Å, V 272.9(1) Å3, and Z=1. It has been refined to an R index of 0.028 on the basis of 342 observed reflections and a correction for the {110} twin law. It is an H-bearing member of the melilite group. The structure has two distinct layers. The one crystallographically distinct Ca site with eight-fold coordination is a square antiprism polyhedron. The Ca polyhedra are in a layer with the H atoms. A second layer consists of corner-sharing Si/Be atoms in tetrahedral coordination with O. One H atom is bonded to an apical O atom that is not shared by two tetrahedra. This H atom is present only when there is a Ca-site vacancy. The other H atom is loosely bonded to the same O atom but at a different site. The IR spectrum supports this H-bonding scheme. Additional hydroxylgugiaite data is given for the other localities.
... Contrary to the initial attempts, a preheating stage at 500°C was applied. The ordering of Si and Be is different in the two mineral species and although gugiaite is tetragonal (Kimata & Ohashi 1982;Yang et al. 2001) and leucophanite orthorhombic but pseudotetragonal (Cannillo et al. 1967;Hawthorne 1989, 2002;Friis et al. 2007a) they have similar lengths of the a axes. This strong structural relationship between the two minerals makes them difficult to distinguish based on XRD, especially since the degree of order in the synthetic material is not known. ...
... Within the melilite group, the crystal structures of several minerals have been refined; of particular interest in the present case are gehlenite, Ca 2 Al(Si,Al) 2 O 7 (Louisnathan 1971) and gugiaite, Ca 2 BeSi 2 O 7 (Yang et al. 2001). These isomorphous structures have spacegroup symmetry P42 1 m; in gehlenite, Al occupies the T1 site with point symmetry 4 , and the T2 site (with point symmetry m) is occupied by Al ½ Si ½ ; in gugiaite, Be occupies the T1 and Si the T2 sites. ...
We have made new chemical analyses of a large number of samples of meliphanite from Norway and of leucophanite from both Norway and Mont Saint-Hilaire, Quebec. Infrared spectra were collected on a sample of each mineral to confirm the lack of (OH) groups, inferred on the basis of absence of any absorption bands in the OH-stretch region. Four samples were chosen for crystal-structure analyses, two crystals of meliphanite from localities in Norway and two leucophanite samples (one REE-rich) from Mont Saint-Hilaire, Quebec. The anomalous biaxial character of tetragonal meliphanite is likely due to stress within the crystal structure as a result of twinning. The crystal structure of meliphanite from Arøy, Norway is presented in detail, as this represents material used in the early description of this mineral. It is tetragonal I4̅, a 10.5257(3), c 9.8868(4) Å, V 1095.37(8) ų and Z = 2. The structure refined to R = 0.025 using 1578 observed (>4σ Fo) reflections. The crystal-structure analysis established the simplified formula Ca4(Na,Ca)4Be4AlSi7O24(F,O)4; the essential Al orders in the layer of tetrahedra, which differentiates it from leucophanite, Ca4Na4Be4Si8O24F4. Meliphanite is structurally related to the melilite group of minerals, in which the topology of the layer of tetrahedra defines a two-dimensional net (5³)(5⁴). The expansion of this series of structures from melilite to leucophanite to meliphanite requires subtle modifications in this net to accommodate cation order, both among the larger cations and the small tetrahedrally coordinated cations. This ordering is dictated by local bond-valence requirements.
The first barium member of the melilite group, bennesherite Ba2Fe2+Si2O7 [P421m, Z = 2, a = 8.2334(14) Å, c = 5.2854(8) Å, V = 359.29(13) Å3], was discovered in thin veins of rankinite paralava within pyrometamorphic gehlenite hornfels at Gurim Anticline, Hatrurim Basin, Negev Desert, Israel. Bennesherite occurs in small intergranular spaces between large crystals of rankinite, gehlenite, and garnet together with other Ba-minerals such as fresnoite, walstromite, zadovite, gurimite, hexacelsian, and celsian. It forms transparent, light yellow to lemon-colored crystals with a white streak and a vitreous luster. They exhibit good cleavage on (001), a brittle tenacity, and a conchoidal fracture. The estimated Mohs hardness is 5. Bennesherite has a melilite-type structure with the layers composed of disilicate (Si2O7)6− groups and (Fe2+O4)6− tetrahedra, connected by large eightfold-coordinated Ba atoms. In some grains, epitaxial intergrowths of bennesherite and fresnoite are observed. The structure of the fresnoite, Ba2TiO(Si2O7) with a P4bm space group and unit-cell parameters a = 8.5262(5) Å, c = 5.2199(4) Å, is closely related to the structure of bennesherite. Among all the known minerals of the melilite group, bennesherite has a structure characterized by the lowest misfit degree between the tetrahedral (T1 and T2 sites) and polyhedral (X-site) layers, as it was shown in both natural and synthetic melilite-type phases.
In 1996, in collaboration with Lawrence Anovitz, I edited Boron Mineralogy, Petrology and Geochemistry , volume 33 in the Reviews in Mineralogy series, a book that has been reprinted with addenda in 2002 (further addenda and corrections are posted at http://www.minsocam.org, where you may also find corrections to this volume). Many of the same reasons for inviting investigators to contribute to a volume on boron apply equally to a volume on beryllium. Like B, Be poses analytical difficulties, and it has been neglected in many geochemical, mineralogical and petrological studies. However, with the development of instruments to measure cosmogenic isotopes, greater availability and refinement of the ion microprobe, and with overall improvement in analytical technology, interest in Be and its cosmogenic isotopes has increased, and more studies are being published. Thus, I decided that it was an appropriate time to invite those actively involved in research on Be to contribute to this volume, which is intended to be a companion to Boron Mineralogy, Petrology and Geochemistry . NOTE: In this chapter, individual review papers are referred to by author name(s) and chapter number.
The Be mineral beryl and its colored variants emerald, aquamarine, and “chrysoberyl” (= golden beryl, not the present chrysoberyl) were known to the ancients, and Pliny the Elder had noted that many persons considered emerald and beryl “to be of the same nature” (Sinkankas 1981, p. 20; also Dana 1892; Weeks and Leicester 1968). However, not until 1798 was it realized that beryl contained a previously unknown constituent; analyses before then yielded only silica, alumina, lime and minor iron oxide (Vauquelin 1798; Anonymous 1930; Weeks and Leicester 1968; Greenwood and Earnshaw 1997). The mineralogist Rene Just Hauy asked Nicolas Louis Vauquelin (Fig. 1⇓) to analyze beryl and emerald in order to …
Quadratic elongation and the variance of bond angles are linearly correlated for distorted octahedral and tetrachedral corrdination
complexes, both of which show variations in bond length and bond angle. The quadratic elongation is dimensionless, giving
a quantitative measure of polyhedral disortion which is independent of the effective size of the polyhedron.