ABSTRACT

TRICLINIC Na3Al(V10O28) ∙ 22H2O, A NEW MEMBER OF THE PASCOITE GROUP OF MINERALS FROM THE SUNDAY MINE, SAN MIGUEL CO., CO.

by Gregory R. Schmidt

This paper reports the discovery, description and structure solution of the new member of the pascoite family of minerals from the Sunday Mine in San Miguel County, Colorado. Optical, chemical, x-ray diffraction, Raman, as well as theoretical charge density data are presented. M1 Having an ideal chemistry of Na3AlV10O28 ∙ 22H2O, the calculated chemistry of (Na0.6,Mg0.4) M2 (Na1.25,Mg0.63, 0.12) AlV10O28 ∙ 22H2O is based on the structure solution. The structure is triclinic with space group P1 and a cell of a = 8.6680, b = 10.2946, c = 12.9076, α = 105.826, β = 97.899 and γ = 103.385. The atomic arrangement consists of two units, the structural unit -6 which contains the decavanadate (V10O28) polyanion, and the fully hydrated interstitial unit. Of particular interest in this study is the presence of a six-coordinated oxygen which sits within the center of the decavanadate polyanion. All 6 bonded interactions were found using theoretical charge density calculations.

TRICLINIC Na3Al(V10O28) ∙ 22H2O, A NEW MEMBER OF THE PASCOITE GROUP OF MINERALS FROM THE SUNDAY MINE, SAN MIGUEL CO., CO.

A Thesis

Submitted to the Faculty of Miami University in partial fulfillment of the requirements for the degree of Master of Science Department of Geology by Gregory R. Schmidt Miami University Oxford, Ohio 2009

Advisor______Dr. John Rakovan

Reader______Dr. Elisabeth Widom

Reader______Dr. Hailiang Dong

TABLE OF CONTENTS

Introduction 1 Occurrence 1 Appearance and Optical Properties 2 Chemistry 3 Experimental Procedures 4 Atomic Arrangement 5 Raman Spectroscopy 7 Charge Density 7 References 9

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LIST OF TABLES

Table 1: Neutral oxide weight percents calculated from site scattering diffraction data. Table 2: Refinement parameters for hughesite. Table 3: Atomic positions Table 4: Bond lengths and valences Table 5: Anisotropic thermal parameters. Table 6: Bond valence analysis of the O13 site. Table 7: Indexed Raman peaks. Table 8: Charge density analysis of the O13 BCP.

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LIST OF FIGURES

Figure 1: Hughesite mounted on glass fiber.

Figure 2: Decavanadate polyanion of hughesite.

Figure 3: Ball-stick (left) and polyhedral (right) models of the hughesite structure viewed along [010].

Figure 4: Geometry of the O13 site in hughesite.

Figure 5: Raman spectra of hughesite.

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Acknowledgements

This thesis would not be possible without the help and support of Mickey Gunter, Joe Marty and William S. Wise who provided samples as well as significant analytical data not acquired at Miami University. Thanks are also given to Olaf Borkiewicz and Tomasz Marchlewski who provided time and insight into SEM data collected. Raman data was collected at the Molecular Microspectroscopy Laboratory (MML) in the department of chemistry and biochemistry. Finally, thanks are due to my advisor John Rakovan, and committee members Hailiang Dong and Elisabeth Widom.

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Introduction

Pascoite group minerals occur as secondary formations resulting from the oxidation of vanadium ores contained in sedimentary rocks. Bright-yellow to orange in color, the pascoite group includes the minerals: pascoite, Ca3(V10O28) ∙ 17H2O (Hughes et al. 2005); hummerite,

K2Mg2(V10O28) ∙ 16H2O (Hughes et al. 2002); lasalite Na2Mg2(V10O28) ∙ 20H2O (Hughes et al.

2007); and possibly huemulite, Na4Mg(V10O28) ∙ 24H2O (Gordillo et al 1966), the structure of 6- which has not been determined. Common to each of these minerals is the [V10O28] decavanadate anionic complex, which is observed to be weakly bonded to alkali and alkali-earth cations as well as H2O molecules (Hughes et al. 2007). Collecting, by Joe Marty, at the Sunday Mine, San Miguel County, Slick Rock District, Colorado, USA, yielded several samples presumed to be huemulite. However, unit cell parameters measured through single crystal X- ray-diffraction did not match that of huemulite or any other known phase. Data presented in this paper show that this is a new mineral and member of the pascoite group of minerals. We are pleased to name this mineral hughesite in honor of Dr. John M. Hughes, for his long and outstanding career in mineralogy as well as his extensive work on the pascoite group of minerals, and vanadium bronzes. The mineral has been submitted as a new species to the Commission on New Minerals, Nomenclature and Classification (CNMNC) of the International Mineralogical Association (IMA). We also present the results of charge density calculations for the decavanadate complex, common to all pascoite group minerals. Studying this mineral not only provides us with information about a new mineral within the pascoite group, but also lends to the ability to suggest an ore system based upon its secondary minerals.

Occurrence

Hughesite, which has also been found in other parts of the Sunday Mine Complex, occurs as crusts on the sandstone walls of the mine workings and in fractures in the rock. The mineral forms through the oxidation of corvusite, the primary vanadium oxide phase present, as it reacts with ground waters. Mineralization occurs during evaporation of this liquid leaving a crust of hughesite and other vanadium minerals on the surface of the host rock.

The Sunday Mine complex is part of the Uravan mineral belt, an arcuate zone of uranium-vanadium deposits in San Miguel, Montrose, and Mesa counties, Colorado, and Grand

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County, Utah. It was the most productive uranium mining area in the United States in the early 20th century. The mineral belt includes the Slick Rock, Gypsum Valley, Uravan, and Gateway mining districts (Fischer and Hilpert, 1952). Uranium and vanadium minerals formed irregularly shaped ore deposits, commonly referred to as uranium rolls, contained within Jurassic Morrison sandstones.

Epigenetic deposits of uranium in sedimentary rocks form the bulk of uranium deposits in Colorado. These include the many mines of the Uravan, Cochetopa, Maybell, and Rifle districts, and other scattered places including the Front Range and Denver Basin. Epigenetic uranium deposits in the sandstones of the Salt Wash Member of the Jurassic-age Morrison Formation were formed when vanadium-bearing waters, probably derived from the overlying volcanic ash beds, flowed through the sandstones. The uranium- and vanadium-bearing water met changing physicochemical conditions, such as a reducing zone occupied by fossil organic material or changes in the acidity of the water, and the uranium precipitated as the minerals uraninite or coffinite and vanadium precipitated with clay minerals (Cappa, 2006).

Major ore and associated minerals include; carnotite, the major uranium ore, rossite, hewettite, sherwoodite, corvusite, and montroseite, all major vanadium ore sources. The majority of vanadium ore minerals are pentavanadates (V2O5), and are processed after uranium production has occurred.

Appearance and Optical Properties of Hughesite

Efflorescent crusts of hughesite, and other related minerals, have been measured to be between 1 and 3 mm thick. The surface of samples glistens from exposed crystal faces, with very minimal rounding from dissolution observed. In some instances, single crystals up to 2 mm in length were found.

Hughesite is orange to golden orange in color and streaks yellow. The thinnest layers of hughesite appear orange, where the thickest layers are golden orange in color. Crystals are transparent with an adamantine luster. It is highly soluble in water, acetone and alcohol, making it difficult to handle for analytical work.

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Optical properties of hughesite were determined from a single crystal with known orientation, determined by X-ray diffraction, mounted on a goniometer head. Hughesite is Biaxial negative with α = 1.698(5), β = 1.740( 5), γ = 1.770(5) using 589 nm. The measured 2V is 84(2)˚ and calculated equal to 78.7˚. It has a strong dispersion with r > v. Hughsite is pleochroic with X = Y = light golden yellow: Z = dark golden yellow. Its absorption is characterized by Z > Y = X.

Chemistry of Hughesite

Chemical analysis proved difficult because of the instability of the mineral under the electron beam in vacuum. By use of a variable pressure scanning electron microscope (SEM), operated at high chamber pressure, and by analyzing areas rather than individual spots we were able to collect stable X-ray fluorescence data with an energy dispersive spectrometry (EDS) detector. Multiple areas on four different crystals (a total of 10 different analyses) yield essentially identical results. Because of the solubility of the crystals they were not mounted in epoxy and polished, but rather analyzed as rough crystals set on top of carbon tape. The EDS data were used for semi-quantitative chemical analysis. EDS shows the clear presence of major M1 M2 Na, Mg, Al, V and O. The chemical formula (Na0.6,Mg0.4) (Na1.25,Mg0.63, 0.12) AlV10O28 ∙

22H2O is based on the semi-quantitative chemical analysis, refined by crystal structure analysis (evaluation of site scattering, modeled site occupancies, and bond length evaluation). The ideal formula is Na3AlV10O28 ∙ 22H2O.

Structure solution shows that there are a total of 50 oxygen atoms in the unit cell of which 22 are associated with water molecules. Thus, the chemical formula is based on 50 oxygens. Site scattering and bond distances show that the Al and V sites are fully occupied by these atoms. Site assignment of Mg and refinement of the Na/Mg ratios was more problematic. Given the available cation sites, the two M-sites are the ones most likely to accommodate Na and Mg. This, however, is an unusual pairing given the size differences of these ions. Na+ and Mg2+ are isoelectronic and thus are difficult to differentiate by site scattering. We estimated the Na/Mg ratios (and occupancies) in the two M sites based on bond distances compared to those found in the related mineral lasalite (Hughes et al., 2008). In lasalite there are distinct Na and Mg

3 octahedral sites. We assumed that the average bond distance of each of the two M sites in hughesite is an average of the average Na-O and Mg-O bond distances found in lasalite weighted by the abundance of Na and Mg on the site. The amount of Na and Mg in each site was calculated assuming full site occupancy.

In the structure refinement the occupancy of all cations sites was refined. The M1 and M2 sites were refined using the Na scattering factor. The M1 site occupancy refined to 0.998 (i.e. fully occupied) and the M2 site occupancy refined to 0.9610. The diminution in site scattering on M2 is assumed to be the result of vacancies, which would allow charge balance of Mg2+ substitution for Na+. We therefore decreased the Na occupancy by 0.12 in the M2 site of the chemical formula. The coupled substitution is therefore modeled as 2Na ↔ Mg + Based on this formula there are 100 negative charges and 100.1 positive charges. The discrepancy is believed to be within analytical error. The neutral oxide weigh percents listed in Table 1 are those determined by the semi quantitative EDS analyses. If these are calculated from the M1 M2 chemical formula, determined as described above, (Na0.6,Mg0.4) (Na1.25,Mg0.63, 0.12)

AlV10O28 ∙ 22H2O, we get Na2O 3.94, MgO 2.85, Al2O3 3.50, V2O5 62.47, H2O 27.23.

Crystal Structure: Experimental

A crystal of hughesite (Figure 1) was mounted on a Bruker Apex CCD diffractometer equipped with graphite-monochromated Mo Kα radiation. Refined cell-parameters and other crystal data are reported in Table 2. Data were collected for a full sphere of reciprocal space, and absorption corrections were applied using semi-empirical methods using the SADABS (Bruker AXS, Inc. 2003) program. Data were integrated as well as corrected for Lorentz and polarization factors using the program SAINTPLUS (Bruker AXS, Inc. 2003).

The structure was solved by Direct Methods and difference Fourier maps using the Bruker SHELXTL v. 6.14 (Bruker AXS, Inc. 2000) package of programs. Neutral- atom scattering factors and terms for anomalous dispersion were employed throughout the solution and refinement. The structure was refined on F2 with anisotropic thermal parameters for all non- hydrogen atoms. The hydrogen atoms in hughesite were easily located using Direct Methods. Atomic parameters are listed in Table 3 and the selected interatomic distances along with bond

4 valences in Table 4. Anisotropic thermal parameters for all non-hydrogen atoms are listed in Table 5.

Raman spectra were collected on a crystal with dimensions 80 x 50 x 50 m on a Renishaw Invia confocal Raman microprobe. The sample was excited with a 785 nm diode laser. This source was focused onto the sample using a 50X (0.85 N.A.) objective, which produced an approximate beam diameter of two microns at the sample. The same objective was employed to collect the scattered radiation. Spectra were collected at 4 cm-1 resolution and represent the average of 2 individual scans. The integration time for each spectral element was 20 seconds. The power did not exceed 6 milliwatts at the sample.

Common to all pascoite group minerals is the decavanadte anionic complex. At the center of this complex reside two six coordinated oxygen atoms. As noted by Hughes et al., (2002) this is an unusual coordination for oxygen, particularly when bonded to highly charged V5+. Thus, it was decided to analyze the decavandate anionic complex, specifically the six coordinated oxygen atoms using charge density techniques. Due to the observed lengthening of the V—O13 bond distance from the structure solution, as well as the unusual coordination, calculations were done to explore the properties of the bonded interactions to [VI]O13.

A model of the decavanadate molecule was created from atomic positions refined in the hughesite structure and imported into GAUSSIAN03 (Frisch et al., 2004) and GAMESS (Schmidt et al., 1993). Theoretical charge density data were calculated at the rhf/6-311g level of theory. A density functional theory, DFT, analysis was also performed at the B3LYP/6-311g level. Resulting wave functions were then imported into the AIMALL (Keith, 2009) package, a highly modified version of the AIMPAC suite of software by Bader et al., (1994). Local electron density and Laplacian distributions were calculated for the V—O bonded interactions with careful attention paid to the six coordinated O atoms in the center of the decavanadate polyanion.

Atomic Arrangement of Hughesite

Hughesite is triclinic with space group P1 and a cell of a = 8.6680, b = 10.2946, c = 12.9076, α = 105.826, β = 97.899 and γ = 103.385. The atomic arrangement of minerals

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6- containing the decavanadate polyanion (V10O28) , as noted by Hughes et al. (2005), definitively illustrate the bipartite nature of mineral structures described by Hawthorne (1983). In his work, Hawthorne recognized two parts of complex mineral structures: i) the structural unit; the anionic portion of the structure which contains higher-valence bonds, and ii) the interstitial complex; the cationic part of the structure which contains lower-valence bonds between alkaline and alkaline- earth cations and (H2O), (OH), and/or Cl groups. Using Hawthorne’s (1983) observations, Schindler et al. (2000a) described the nature of bonding between the two distinct parts of the structure. Below are the descriptions of the anhydrous, polyanion structural unit and the hydrated interstitial complex in hughesite. Bond valence calculations were performed for each cation site and are presented in Table 6.

Structural unit

The decavanadate polyanion complex in hughesite is shown in Figure 2. As found in other pascoite group minerals, the complex if formed of ten distorted, edge-sharing octahedra (Swallow et al., 1966), and is found in numerous synthetic vanadate compounds (Ferreira da Silva et al., 2002; Hughes et al., 2005) The complex consists primarily of octahedrally coordinated V atoms with the bridging oxygens being either 2- or 3-coordinated.

The vanadyl bond, defined by Schindler et al., (2000), is a V5+-O bond of length less than 1.74 Å. Each vanadium octahedra in hughesite contains one vadanyl bond except for the V1 octahedra, which contains two. In the V2-V5 octahedra the vadanyl bond is trans to the long V- O bond, and the remaining four bonds are approximately equal in length. This bond topology is characteristic of the decavanadate group observed in pascoite group minerals (Hughes et al., 2008).

In hughesite, atom O2, an exterior atom of the polyanion complex bonds to Na2 of the interstitial unit, while the other exterior oxygen atoms of the decavanadate complex bond to the interstitial unit through hydrogen bonding. Of particular interest in the decavanadate group is the presence of one ―interior‖ oxygen atom which exhibits a six-coordinated bonded geometry as noted by Hughes et al., (2002). Oxygen atom O13 bonds to six vanadium atoms, which is a curious coordination for oxygen in general, even more unusual when bonded to a pentavalent cation. As observed in each V-octahedron, the O13-V bond is the longest bond in the polyhedra,

6 and as such it has the lowest valence in the polyhedra. The bond valence sum for O13 is 1.957 (v.u.), thus, while having an atypical coordination, the applicability of the valence-matching principle is maintained for the six coordinated O13.

The interstitial unit in hughesite

The arrangement of structural units in the unit cell of hughesite is shown in Figure 3. The interstitial unit links the anhydrous decavanadate structural units. The interstitial unit, the hydrated portion of the atomic arrangement, is comprised of two separate components. First is the Na3H28O14 trimer. The trimer consists of two separate crystallographic sites: M1 and M2. Both sites are primarily filled by Na, but experience significant Mg substitution. The second part of the interstitial unit is the AlH12O6 monomer, which resides in the center of the unit cell. The monomer sits roughly in the AB plane and is surrounded by four decavanadate groups, bonding solely to terminal oxygens of the decavanadate groups through hydrogen bonding. The two components of the interstitial unit are separated and not directly bonded to each other. All of the oxygen atoms in the interstitial unit are water molecules; thus the interstitial unit is fully hydrated. Atoms O24 and O25 bond to the remainder of the structure solely through hydrogen bonding.

Raman Spectroscopic Analysis of Hughesite

Raman analysis of hughesite (Figure 5) attests to the six coordinated nature of the O13 atom. At the V-O stretching region, we notice the presence of a split peak. This is due to the disparity in the bond lengths between the six coordinated and two coordinated O geometries. The lower wave number peak located at 963.63 cm-1 is due to the six coordinated V-O13 bonded interactions and the higher wave number peak is from the other V-O bonded interactions in the structure. It is possible to make such peak assignments because of the unusual nature of the bonding between V and O13. All O atoms in the structural unit except O13 are bonded to either two or three V atoms. These bonds are much stronger and therefore vibrate at a higher frequency than the six-coordinated O13. Thus it is expected that the six-coordinated oxygen will exhibit a peak at a lower Raman shift (cm-1) than the rest of the V—O interactions in the structural unit.

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All other peaks are indexed and given in Table 7. No peaks were observed in the OH stretching region, confirming that all the H in the sample is in the form of H2O molecules.

Charge Density Analysis of the Decavanadate Polyanion in Hughesite

The arrangement of atoms in the decavanadate anionic complex, common to all pascoite group minerals, defies our accepted convention of how oxygen should bond to other atoms. Using Pauling’s Rules as a guideline, the oxygen atoms in the structure should not be bonded to more than two cations. However, this is not the case for the O13 atom. It adopts a six coordinated configuration, which is contrary to our accepted convention for how oxygen bonds with other atoms. Due to the geometry around the O13 atom, it was decided to analyze the decavanadate anionic complex, specifically the six coordinated oxygen atoms using charge density techniques. The observed lengthening of the V—O bond lengths from the structure solution make it critical to first determine if all six O13—V interactions are truly bonded interactions. Once determined, the topological analysis of these bonds is studied.

A model of the decavanadate molecule was created and imported into GAUSSIAN03 and GAMESS at the RHF/6-311g level of theory. The focus of the analysis was placed on the six coordinated oxygen atom in the center of the anionic complex. Results were then input into AIMALL, a highly modified version of the AIMPAC software, and a topological analysis of the bonded interactions was performed. From the analysis results (Table 8), it is apparent that the strongest bonds are between O13 and V1. There appears to be very little difference in the overall density between the O13-axial V and the O13- apical V atoms. The low ρ(rc) and high Laplacian values suggest that these bonded interactions are ionic in nature (Gibbs et al., 2006).

Conclusion

Hughesite forms orange to golden orange crystals which occur as crusts on the sandstone walls of the mine workings and in fractures in the rock, forming efflorescent crusts averaging 2 mm thick. The mineral forms through the oxidation of corvusite, the primary vanadium oxide phase present, as it reacts with ground waters. Having an ideal chemistry of Na3AlV10O28 ∙

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M1 M2 22H2O, the calculated chemistry of (Na0.6,Mg0.4) (Na1.25,Mg0.63, 0.12) AlV10O28 ∙ 22H2O is based on the structure solution. The structure is triclinic with space group P1 and a cell of a = 8.6680, b = 10.2946, c = 12.9076, α = 105.826, β = 97.899 and γ = 103.385. The atomic -6 arrangement consists of two units, the structural unit which contains the decavanadate (V10O28) polyanion, and the fully hydrated interstitial unit. Of particular interest in this study is the presence of a six-coordinated oxygen which sits within the center of the decavanadate polyanion. This oxygen bonds to six vanadium atoms, exhibiting extended bond lengths, through ionic bonds. Through the use of theoretical charge density calculations using GAMESS and AIMALL, all 6 bonds were found to have bonded interactions of an ionic nature.

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Evans, H.T. and Konnert, J.A. (1978) The crystal chemistry of sherwoodite, a calcium 14- vanadoaluminate heteropoly complex. American Mineralogist, 63, 863-868.

Ferreira da Silva, J.L., Fátima Minas da Piedade, M., Teresa Duarte, M. (2002) Decavanadates: a building-block for supramolecular assemblies. Inorganica Chimica Acta, 356, 222-242.

Fischer R.P. and L.S. Hilpert (1952) Geology of the Uravan Mineral Belt, US Geological Survey, Bulletin 988-A, 1-13.

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Hughes, J.M., Wise, W.S., Gunter, M.E., Morton, J.P. and Rakovan, J. (2008) Lasalite,

Na2Mg2[V10O28]·20H2O, a new decavanadate mineral species from the Vanadium Queen

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mine, La Sal district, Utah: description, atomic arrangement, and relationship to the pascoite group of minerals. Canadian Mineralogist, 46,1365-1372.

Hughes, J.M., Schindler, M. and Francis, C.A. (2005) The C2/m disordered structure of pascoite,

Ca3[V10O28]·17H2O: bonding between structural units and interstitial complexes in 6- compounds containing the [V10O28] decavanadanate polyanion. Canadian Mineralogist, 43, 1379-1386.

Hughes, J.M., Schindler, M., Rakovan, J.F. and Cureton, F.E. (2002) The crystal structure of

hummerite, K Mg(V5O14).8H2O: bonding between the [V10O28] structural units and the

{K2Mg2(H2O)16} interstitial complex. Canadian Mineralogist, 40,1429-1435.

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Ca3V10O28•17H2O. Acta Crystallographica. 21, 397-405.

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Table 1: Neutral oxide weight percents calculated from site scattering diffraction data.

Constituent Wt.%

Na2O 4.183

MgO 2.845

Al2O3 3.494

V2O5 62.318

H2O 27.160

Total 100.00

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Table 2: Refinement parameters for hughesite:

______Crystal size: 0.12 x 0.10 x 0.08 mm Frame width, scan time, number of frames: 0.20º, 30 s, 4500 -11 =< h =< 11; -13 =< k =< 13; -17 =< l =< 17; 2θ ≤ 56.88º Temperature: 20ºC Detector distance: 5 cm Effective transmission: 0.901461 – 1.000

Rint (before – after SADABS absorption correction): 0.0628 – 0.0424 Measured reflections, unique reflections, full sphere: 16,777; 5,238 Refined parameters: 384, refined on F2 R1 = 0.0496 for 3244 Fo > 4sig(Fo) and 0.0966 for all 5234 data wR2 = 0.0974, GooF = S = 0.908 Largest difference peaks: +0.77, -0.51 e- ∙Å-3 ______

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Table 3: ATOMIC POSITIONS IN HUGHESITE

Site x y z Ueq V1 0.19664(7) 0.07252(7) 0.53427(5) 0.0125(2) V2 0.00684(8) -0.01910(7) 0.70657(5) 0.0140(2) V3 0.05702(8) -0.24605(7) 0.51040(5) 0.0130(2) V4 0.13793(8) 0.29976(7) 0.72602(6) 0.0159(2) V5 0.23092(8) -0.15303(7) 0.33568(6) 0.015(2) O1 0.0777(3) -0.3380(3) 0.5906(2) 0.0205(7) O2 0.0306(3) -0.1114(3) 0.7861(2) 0.0218(7) O3 0.2935(3) 0.2256(3) 0.6399(2) 0.0152(6) O4 0.1426(3) 0.1546(3) 0.7872(2) 0.0160(6) O5 0.0639(3) -0.3000(3) 0.2426(2) 0.0164(6) O6 0.3388(3) 0.0267(3) 0.4679(2) 0.0163(6) O7 0.1205(3) 0.1691(3) 0.4334(2) 0.0116(6) O8 0.3853(3) -0.1811(3) 0.2887(2) 0.0239(7) O9 0.1756(3) -0.0537(3) 0.6175(2) 0.0119(6) O10 0.2318(3) -0.2436(3) 0.4451(2) 0.0155(6) O11 -0.0937(3) -0.3713(3) 0.3912(2) 0.0153(6) O12 -0.1796(3) 0.0251(3) 0.7324(2) 0.0164(6) O13 0.0236(3) -0.0972(3) 0.4164(2) 0.0123(6) O14 0.2603(3) 0.4354(3) 0.8177(2) 0.0273(7) Na1 0.5 0 1 0.0138(6) Na2 0.0840(2) -0.23409(19) 0.91567(14) 0.045(1) Al1 0.5 0.5 0.5 0.0308(7) O15 0.3401(6) -0.2340(5) 0.8678(4) 0.047(1) O16 -0.1577(5) -0.2284(4) 0.9817(3) 0.0361(9) O17 0.2394(5) -0.0098(4) 1.0568(3) 0.0343(9) O18 0.1335(6) -0.3768(5) 1.0298(3) 0.042(1) O19 0.3240(4) 0.3649(4) 0.3938(3) 0.0219(7) O20 0.3641(4) 0.5526(4) 0.5967(3) 0.0225(7) O21 0.4653(4) 0.6348(3) 0.4336(3) 0.0221(7) O22 -0.0907(5) -0.4258(4) 0.7443(3) 0.0314(9) O23 0.4448(6) 0.1295(6) 0.8839(4) 0.054(1) O24 0.3910(6) -0.4946(6) 1.0844(5) 0.097(2) O25 0.4448(6) 0.8361(4) 0.6853(3) 0.0339(9) H15A 0.365(9) -0.234(8) 0.816(6) 0.09(3)

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H15B 0.395(11) -0.276(10) 0.891(7) 0.14(4) H16A -0.229(6) -0.292(5) 0.954(4) 0.02(1) H16B -0.147(5) -0.209(5) 1.048(4) 0.02(1) H17A 0.222(6) -0.007(5) 1.119(4) 0.03(1) H17B 0.209(6) 0.053(5) 1.054(4) 0.02(1) H18A 0.117(8) -0.347(7) 1.085(5) 0.06(2) H18B 0.209(6) -0.411(7) 1.042(6) 0.11(3) H19A 0.264(6) 0.308(6) 0.404(4) 0.04(2) H19B 0.269(5) 0.394(4) 0.353(3) 0.01(1) H20A 0.289(5) 0.514(5) 0.590(3) 0.01(1) H20B 0.385(6) 0.646(6) 0.638(4) 0.05(1) H21A 0.531(6) 0.672(5) 0.408(4) 0.02(1) H21B 0.385(6) 0.667(5) 0.433(4) 0.02(1) H22A -0.093(6) -0.486(5) 0.754(4) 0.02(2) H22B 0.018(11) -0.409(9) 0.693(7) 0.17(4) H23A 0.369(7) 0.140(7) 0.851(5) 0.07(3) H23B 0.492(6) 0.131(5) 0.848(4) 0.02(2) H24A 0.443(7) -0.413(6) 1.054(5) 0.06(2) H24B 0.414(7) -0.554(6) 1.160(5) 0.08(2) H25A 0.544(8) 0.873(7) 0.690(5) 0.07(2) H25B 0.404(7) 0.877(6) 0.675(5) 0.03(2)

15

Table 4: BOND LENGTHS AND BOND VALENCE

V1- O2 1.6772 1.405 V3- O1 1.6004 1.731 O4 1.9731 0.631 O4 2.0191 0.558 O5 1.8929 0.784 O5 2.0147 0.564 O6 1.7172 1.261 O8 1.8306 0.928 O13 2.0796 0.474 O11 1.8223 0.949 O13 2.1413 0.401 O13 2.2417 0.306 Mean: 1.9136 0.826 Mean: 1.9215 0.839 Sum: 4.956(v.u.) Sum: 5.035(v.u.) V2- O3 1.8276 0.936 V4- O3 1.8758 0.821 O4 2.0025 0.583 O6 2.0153 0.563 O5 2.0174 0.560 O9 1.5954 1.753 O7 1.8268 0.938 O10 1.8499 0.881 O13 2.2568 0.293 O11 1.8866 0.798 O14 1.6021 1.721 O13 2.3538 0.226 Mean: 1.9222 0.839 Mean: 1.9295 0.840 Sum: 5.031(v.u.) Sum: 5.042(v.u.) V5- O2 2.0609 0.498 Al- O20x2 1.8893 0.492 O7 1.8709 0.832 O21x2 1.8765 0.500 O8 1.8928 0.785 O22x2 1.8822 0.483 O10 1.8288 0.933 Mean: 1.8827 0.492 O12 1.5965 1.747 Sum: 2.95(v.u.) O13 2.305 0.257 Na2- O16x2 2.4579 0.240 Mean: 1.9258 0.842 O17x2 2.4862 0.170 Sum: 5.052(v.u.) O23x2 2.3312 0.158 Na1- O14 2.4108 0.214 Mean: 2.4251 0.189 O15 2.3741 0.208 Sum: 1.136(v.u.) O16 2.4613 0.193 O17 2.3843 0.193 O18 2.5293 0.169 O19 2.4123 0.140 Mean: 2.4287 0.186 Sum: 1.117(v.u.)

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Table 5: Anisotropic thermal parameters

Atom U11 U22 U33 U12 U13 U23 V1 0.0099(3) 0.0133(4) 0.0161(4) 0.003(3) 0.0031(3) 0.0072(3)

V2 0.0185(4) 0.0141(4) 0.0123(4) 0.0059(3) 0.0045(3) 0.0073(3)

V3 0.0148(3) 0.0124(4) 0.0161(4) 0.0061(3) 0.0056(3) 0.0082(3)

V4 0.0174(4) 0.0141(4) 0.0157(4) 0.0045(3) 0.0034(3) 0.0039(3)

V5 0.0151(3) 0.0182(4) 0.0177(4) 0.0077(3) 0.0077(3) 0.0085(3)

O1 0.023(2) 0.021(2) 0.024(2) 0.009(1) 0.008(1) 0.014(1)

O2 0.030(2) 0.020(2) 0.022(2) 0.010(1) 0.009(1) 0.014(1)

O3 0.011(1) 0.015(2) 0.019(1) 0.002(1) 0.002(1) 0.008(1)

O4 0.020(1) 0.014(2) 0.014(1) 0.005(1) 0.003(1) 0.005(1)

O5 0.021(1) 0.014(2) 0.015(1) 0.008(1) 0.005(1) 0.005(1)

O6 0.010(1) 0.018(2) 0.020(2) 0.004(1) 0.004(1) 0.007(1)

O7 0.012(1) 0.010(1) 0.013(1) 0.003(1) 0.005(1) 0.005(1)

O8 0.025(2) 0.029(2) 0.026(2) 0.015(1) 0.012(1) 0.014(1)

O9 0.013(1) 0.011(1) 0.013(1) 0.003(1) 0.001(1) 0.007(1)

O10 0.017(1) 0.015(2) 0.017(1) 0.008(1) 0.007(1) 0.007(1)

O11 0.014(1) 0.014(2) 0.019(2) 0.005(1) 0.004(1) 0.006(1)

O12 0.017(1) 0.019(2) 0.016(1) 0.006(1) 0.007(1) 0.011(1)

O13 0.009(1) 0.015(2) 0.015(1) 0.003(1) 0.003(1) 0.009(1)

O14 0.027(2) 0.022(2) 0.026(2) 0.002(1) 0.001(1) 0.003(1)

Al1 0.0117(9) 0.011(1) 0.021(1) 0.0039(7) 0.0063(7) 0.0093(8)

Na1 0.031(2) 0.066(2) 0.042(2) 0.010(1) 0.008(1) 0.024(2)

Na2 0.036(1) 0.033(1) 0.027(1) 0.0100(9) 0.0066(8) 0.0149(9)

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O15 0.054(3) 0.054(3) 0.044(3) 0.023(2) 0.021(2) 0.019(2)

O16 0.045(2) 0.040(3) 0.020(2) 0.009(2) 0.011(2) 0.007(2)

O17 0.044(2) 0.039(2) 0.029(2) 0.021(2) 0.017(2) 0.015(2)

O18 0.061(3) 0.049(3) 0.028(2) 0.029(2) 0.015(2) 0.017(2)

O19 0.016(2) 0.020(2) 0.029(2) -0.001(1) 0.001(1) 0.015(2)

O20 0.015(2) 0.018(2) 0.033(2) 0.001(1) 0.012(1) 0.007(2)

O21 0.018(2) 0.020(2) 0.038(2) 0.008(1) 0.012(1) 0.021(2)

O22 0.040(2) 0.024(2) 0.036(2) 0.011(2) 0.011(2) 0.018(2)

O23 0.037(2) 0.102(4) 0.050(3) 0.034(3) 0.019(2) 0.048(3)

O24 0.057(3) 0.077(4) 0.147(6) 0.009(3) -0.004(3) 0.041(4)

O25 0.032(2) 0.027(2) 0.041(2) 0.008(2) 0.005(2) 0.011(2)

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Table 6: Bond valence analysis of the O13 site

O13 Length Valence (s.u.)

V1 2.0797 0.473

V1_1 2.1411 0.401

V2 2.2562 0.294

V3 2.2421 0.305

V4 2.3537 0.226

V5 2.3049 0.258

SUM 1.957

AVG 0.326

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Table 7: Indexed Raman Peaks

Wavenumber (cm-1) absorbance band Source

990.97 1.936E+05 V--O primary Frost et al., 2005 stretching

963.63 1.497E+05 V--O primary Frost et al., 2005 stretching

836.35 1.106E+05 Al--O stretching Bendel & Schmidt, 2008

599.71 1.167E+05 Na--O stretching Schmidt et al., 2006

457.34 1.055E+05 V--O--V bending Frost et al., 2005

412.09 1.039E+05 V--O bending Frost et al., 2005

361.18 1.096E+05 VO3 bending Frost et al., 2005

321.58 1.237E+05 V--O--V bridging Frost et al., 2005

275.38 1.166E+05 V--O bending Frost et al., 2005

236.72 1.442E+05 Na--O bending Schmidt et al., 2005

190.53 1.861E+05 M—O lattice Frost et al., 2005 vibrations

157.53 1.275E+05 M—O lattice Frost et al., 2005 vibrations

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Table 8: Charge density analysis of the O13 BCP.

O13 R-O ρ(rc) laplacian

V1 2.0797 0.7686 3.7147

V1_1 2.1411 0.6182 3.0660

V2 2.2562 0.4724 2.4765

V3 2.2421 0.4902 2.5691

V4 2.3537 0.3727 1.9017

V5 2.3049 0.4350 2.2302

21

Figure 1: Hughesite mounted on glass fiber.

22

Figure 2: Decavanadate polyanion of hughesite.

23

Structural Unit

Figure 3: Ball-stick (left) and polyhedral (right) models of the hughesite structure viewed along [010].

24

Figure 4: Geometry of the O13 site in hughesite with bond distances

25

Figure 5: Raman spectra of hughesite.

26