Electron microscopic studies of modulated structures in (Au,Ag)Te2

Tendeloo, Gustaaf Van; Amelinckx, S.; Gregoriades, P.

doi:10.1016/0022-4596(84)90105-1

Cited by 15 publications

(7 citation statements)

References 4 publications

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“…Sueno et al (1979) and Schutte & de Boer (1988) reported that the incommensurately modulated structure of calaverite is observed at least in the region of 0 < x < 0.15. Krennerite with a range of composition 0.20 < x < 0.28 has been reported by Van Tendeloo et al (1984). In Fig.…”

Section: Chemical Compositionsmentioning

confidence: 70%

Crystal structure, XANES and charge distribution investigation of krennerite and sylvanite: analysis of Au—Te and Te—Te bonds in Au_1–xAg_xTe₂ group minerals

Kitahara¹,

Yoshiasa²,

Tokuda³

et al. 2022

Acta Crystallogr B Struct Sci Cryst Eng Mater

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The structure refinement and XANES study of two gold–silver–tellurides [Au1+x Ag x Te2, krennerite (x = 0.11–0.13) and sylvanite (x = 0.29–0.31)] are presented and the structures are compared with the prototype structure of calaverite (x = 0.08–0.10). Whereas the latter is well known for being incommensurately modulated at ambient conditions, neither krennerite nor sylvanite present any modulation. This is attributed to the presence of relatively strong Te—Te bonds (bond distances < 2.9 Å) in the two minerals, which are absent in calaverite (bond distances > 3.2 Å). In both tellurides, trivalent gold occurs in slightly distorted square planar coordination, whereas monovalent gold, partly substituted by monovalent silver, presents a 2+2+2 coordination, corresponding to distorted rhombic bipyramids. The differentiation between bonding and non-bonding contacts is obtained by computation of the Effective Coordination Number (ECoN). The CHARge DIstribution (CHARDI) analysis is satisfactory for both tellurides but suggests that the Te—Te bond in the [Te3]2− anion is not entirely homopolar. Both tellurides can therefore be described as Madelung-type compounds, despite the presence of Te–Te in both structures.

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Section: Chemical Compositionsmentioning

confidence: 70%

Crystal structure, XANES and charge distribution investigation of krennerite and sylvanite: analysis of Au—Te and Te—Te bonds in Au_1–xAg_xTe₂ group minerals

Kitahara¹,

Yoshiasa²,

Tokuda³

et al. 2022

Acta Crystallogr B Struct Sci Cryst Eng Mater

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“…2). Our investigation of the natural minerals in the series Au 1-x Ag x Te 2 completes other studies on calaverite (Pertlik 1984a;Schutte and Boer 1988;van tendeloo et al 1983a;Reithmayer et al 1993), sylvanite (Van Tendeloo et al 1983bPertlik 1984c), and krennerite (Van Tendeloo et al 1984;Pertlik 1984b). All these examples taken together show that different degrees of valence fluctuations on the Au-position are possible and, further, these fluctuations can induce the structure modulation.…”

Section: Crystal Chemistry and Structure Modulationsmentioning

confidence: 70%

“…The mineral kostovite (CuAuTe 4 ; Van Tendeloo and Amelinckx 1986) is isostructural with sylvanite and can also be included in the calaverite (3+1) D family. The structure of krennerite, Ag 0.2 Au 0.8 Te 2 , can be described as calaverite with ordered twin m-mirror planes leading to orthorhombic symmetry (Van Tendeloo et al 1984). Some synthetic compounds can also be described in the calaverite (3+1)D structure type.…”

Section: The Calaverite (3+1)d Structure-type Familymentioning

confidence: 99%

The role of silver on the stabilization of the incommensurately modulated structure in calaverite, AuTe2

Bindi¹,

Arakcheeva

Chapuis

2009

American Mineralogist

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Structural investigations of several minerals belonging to the calaverite group with composition Au 1-x Ag x Te 2 (x = 0.00, 0.02, 0.05, 0.09, 0.19, and 0.33) indicate that Ag is randomly distributed on the Au sites. This suppresses the valence fluctuation of Au and, therefore, the structure modulations. The results are compared with the previously published incommensurately modulated structure of calaverite, Au 0.9 Ag 0.1 Te 2 , which is characterized by valence fluctuations of Au reinforced by an ordered distribution of Ag. The (3+1)-dimensional calaverite structure type is able to reproduce both (3+1)D and 3D related structures with the general formula AB 2 (A = Au, Ag, Cu, Nb, Ta; B = Te).

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“…This is not surprising considering the close similarity between the crystal structures of several species in the system Au-Ag-Te (Bindi, 2008, and references therein). Ideal sylvanite has the commensurate modulated superstructure of calaverite but non-stoichiometry induces periodic displacements and periodic antiphase boundaries (van Tendeloo et al, 1983(van Tendeloo et al, , 1984. The small size of the inclusion discussed here hampers further insight into the crystal structural modularity.…”

Section: High-resolution Imaging: Phase Identificationmentioning

confidence: 91%

Lifting the cloak of invisibility: Gold in pyrite from the Olympic Dam Cu-U-Au-Ag deposit, South Australia

Ehrig

Ciobanu

Verdugo-Ihl

et al. 2023

American Mineralogist

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Invisible gold' refers to gold (Au) occurring either within the lattice of a host sulfide or as discrete nanoparticles (NPs, <100 nm-diameter) within a host that are only observable when imaged at higher magnifications. Previous research has regarded the physical form of invisible gold to be partially controlled by the concentration of arsenic (As) in the host sulfide, with stability fields for latticebound versus Au-NPs defined by an empirical Au-As solubility curve. We undertook micron-and nanoscale analysis of a representative sample of As-Co-Ni-(Au)-bearing pyrite from Cu-mineralized breccias in the deeper part of the Olympic Dam Cu-U-Au-Ag deposit (South Australia) to define the location and physical form of Au and accompanying elements. Trace element geochemistry and statistical analysis show that >50% of pyrites contain measurable Au and As, and plot below the Au-As solubility curve. Gold and As are geochemically associated with Te, Bi, Pb, Ag and Sn. Primary oscillatory zoning patterns in pyrite defined by As-Co-Ni are reshaped by processes of dissolution-* Corresponding author.

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Electron microscopic studies of modulated structures in (Au,Ag)Te2

Cited by 15 publications

References 4 publications

Crystal structure, XANES and charge distribution investigation of krennerite and sylvanite: analysis of Au—Te and Te—Te bonds in Au_1–xAg_xTe₂ group minerals

Crystal structure, XANES and charge distribution investigation of krennerite and sylvanite: analysis of Au—Te and Te—Te bonds in Au_1–xAg_xTe₂ group minerals

The role of silver on the stabilization of the incommensurately modulated structure in calaverite, AuTe2

Lifting the cloak of invisibility: Gold in pyrite from the Olympic Dam Cu-U-Au-Ag deposit, South Australia

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Electron microscopic studies of modulated structures in (Au,Ag)Te2

Cited by 15 publications

References 4 publications

Crystal structure, XANES and charge distribution investigation of krennerite and sylvanite: analysis of Au—Te and Te—Te bonds in Au1–x Ag x Te2 group minerals

Crystal structure, XANES and charge distribution investigation of krennerite and sylvanite: analysis of Au—Te and Te—Te bonds in Au1–x Ag x Te2 group minerals

The role of silver on the stabilization of the incommensurately modulated structure in calaverite, AuTe2

Lifting the cloak of invisibility: Gold in pyrite from the Olympic Dam Cu-U-Au-Ag deposit, South Australia

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Product

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About

Crystal structure, XANES and charge distribution investigation of krennerite and sylvanite: analysis of Au—Te and Te—Te bonds in Au_1–xAg_xTe₂ group minerals

Crystal structure, XANES and charge distribution investigation of krennerite and sylvanite: analysis of Au—Te and Te—Te bonds in Au_1–xAg_xTe₂ group minerals