Spectroscopic studies of spessartine from Brazilian pegmatites

Eeckhout, S. G.; Castañeda, Cristiane; Ferreira, Ana Cláudia Mousinho; Sabioni, Antônio Claret Soares; Grave, E. De; Vasconcelos, Daniela C.L.

doi:10.2138/am-2002-1005

Cited by 10 publications

(6 citation statements)

References 17 publications

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“…The experimental spectra and three-component fits are shown in Figure 4. The high IS, high QS doublet characteristic of Fe 2+ in either 6-or 8-coordination, which typically has QS ∼3.5 (Woodland and O'Neill 1993;Eeckhout et al 2002;Geiger et al 2003;Taran et al 2007;Woodland et al 2009) was completely absent from all spectra, further confirming that no Fe 2+ was present in our samples.…”

Section: Mössbauer Spectroscopysupporting

confidence: 68%

“…These values are presented without error bars because rather than being direct measurements, they are the optimized values yielding the best fit to the spectroscopic data as shown in the residuals in Figure 4. [Data sources: Amthauer et al (1976), O'Neill (1993), Fei et al (1994), Eeckhout et al (2002), Geiger et al (2003), McCammon et al (2004), Sharma et al (2007), Taran et al (2007), Grew et al (2008), Woodland et al (2009).] (Color online.)…”

Section: Power X-ray Diffractionmentioning

confidence: 99%

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Synthesis and crystal chemistry of Fe3+-bearing (Mg,Fe3+)(Si,Fe3+)O3 perovskite

Hummer

Fei

2012

American Mineralogist

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We have synthesized magnesium-iron silicate perovskites with the general formula Mg 1-x Fe 3+ x+y Si 1-y O 3 , in which the iron cation is exclusively trivalent. To investigate the crystal chemistry of Fe 3+ -bearing perovskite, six samples (both with and without Al) were analyzed using scanning electron microscopy, electron microprobe, X-ray diffraction, and Mössbauer spectroscopy. Results indicate that Fe 3+ substitutes significantly into both the octahedral and dodecahedral sites in the orthorhombic perovskite structure, but prefers the octahedral site at Fe 3+ concentrations between 0.04 and 0.05 Fe per formula unit, and the dodecahedral site at higher Fe 3+ concentrations. We propose a model in which Fe 3+ in the A/B site (in excess of that produced by charge coupled substitution) is accommodated by Mg/O vacancies. Hyperfine parameters refined from the Mössbauer spectra also indicate that a portion of dodecahedral sites undergo significant structural distortion. The presence of Fe 3+ in the perovskite structure increases the unit-cell volume substantially compared to either the Mg end-member, or Fe 2+ -bearing perovskite, and the addition of Al did not significantly alter the volume. Implications for increased compressibility and a partially suppressed spin transition of Fe 3+ in lower mantle perovskite are also discussed.

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Section: Mössbauer Spectroscopysupporting

confidence: 68%

Section: Power X-ray Diffractionmentioning

confidence: 99%

Synthesis and crystal chemistry of Fe3+-bearing (Mg,Fe3+)(Si,Fe3+)O3 perovskite

Hummer

Fei

2012

American Mineralogist

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“…The compositions of garnets lying in the pyralspite range (see Table Ia and Figure 2), namely pyrope (variety chrome pyrope), almandine, pyrope-almandine (variety rhodolite), spessartine and almandinespessartine are consistent with those in the literature (Deer et al, 1997;Eeckhout et al, 2002). The pyrope-spessartine variety known by some in the gem trade as 'malaya garnet' contains 52.75 mol.% pyrope, 33.65 mol.% spessartine, 6.10 mol.% grossular and 7.50 mol.% almandine (sample 9), which is consistent with results reported by Schmetzer et al (2001), and shows just small contents of Cr 3+ and V 3+ .…”

Section: Chemical Compositionsupporting

confidence: 87%

Formation of large synthetic zincite (ZnO) crystals during production of zinc white

Nowak¹,

Braithwaite²,

Nowak³

et al. 2007

Journ of Gemm

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Remarkable zincite crystals have formed as a by-product of zinc white production in Olawa Foundry, Poland. Some are of gem quality and have been faceted. Small primary crystals formed by reaction of zinc vapour with carbon dioxide from fuel burning gases leaking through faults in a diaphragm of a retort furnace. Some of these have undergone carbon monoxide-promoted and zinc vapour-assisted sublimation to form large secondary crystals. Many of these crystals are brightly coloured and transparent, and have been found up to 2 kg in weight. Most of the crystals are fluorescent in ultraviolet light.

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“…In a comprehensive IR study of the hydrogrossular series, Rossman and Aines (1991) reported that samples containing substantial H (>11.7 wt% H 2 O equivalent to >5.43 OH per formula unit) gave spectra consistent with the substitution 4H+ Z o → o+ Z Si, whereas samples with much less H (<3.6 wt% H 2 O, mostly <0.5 wt%) gave 7 different types of IR spectra, suggesting OH groups were present in multiple site environments, an inference supported by NMR spectra on three grossular samples (Cho and Rossman 1993). On the basis of Fourier-transform IR spectra, Eeckhout et al (2002) concluded that there is no evidence for a multisite OH substitution in spessartine-almandine garnets from Brazilian pegmatites, leaving the hydrogarnet substitution as the only proposed mechanism for the incorporation of H. In summary, garnet samples in which concentrations of H are too low to be studied by conventional X-ray and neutron diffraction techniques give conflicting and equivocal results, whereas Hrich samples in which H can be determined by these techniques give data consistent with 4H+ Z o → o+ Z Si. Consequently, for nomenclature purposes, we have assumed that H is incorporated exclusively by…”

Section: Aspects Of Garnet-supergroup Mineralsmentioning

confidence: 99%

Nomenclature of the garnet supergroup

Grew

Locock

Mills

et al. 2013

American Mineralogist

232

216

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The garnet supergroup includes all minerals isostructural with garnet regardless of what elements occupy the four atomic sites, i.e., the supergroup includes several chemical classes. There are presently 32 approved species, with an additional 5 possible species needing further study to be approved. The general formula for the garnet supergroup minerals is {X 3 }[Y 2 ](Z 3)ϕ 12 , where X, Y, and Z refer to dodecahedral, octahedral, and tetrahedral sites, respectively, and ϕ is O, OH, or F. Most garnets are cubic, space group Ia3d (no. 230), but two OH-bearing species (henritermierite and holtstamite) have tetragonal symmetry, space group, I4 1 /acd (no. 142), and their X, Z, and ϕ sites are split into more symmetrically unique atomic positions. Total charge at the Z site and symmetry are criteria for distinguishing groups, whereas the dominant-constituent and dominant-valency rules are critical in identifying species. Twenty-nine species belong to one of five groups: the tetragonal henritermierite group and the isometric bitikleite, schorlomite, garnet, and berzeliite groups with a total charge at Z of 8 (silicate), 9 (oxide), 10 (silicate), 12 (silicate), and 15 (vanadate, arsenate), respectively. Three species are single representatives of potential groups in which Z is vacant or occupied by monovalent (halide, hydroxide) or divalent cations (oxide). We recommend that suffixes (other than Levinson modifiers) not be used in naming minerals in the garnet supergroup. Existing names with suffixes have been replaced with new root names where necessary: bitikleite-(SnAl) to bitikleite, bitikleite-(SnFe) to dzhuluite, bitikleite-(ZrFe) to usturite, and elbrusite-(Zr) to elbrusite. The name hibschite has been discredited in favor of grossular as Si is the dominant cation at the Z site. Twenty-one end-members have been reported as subordinate components in minerals of the garnet supergroup of which six have been reported in amounts up to 20 mol% or more, and, thus, there is potential for more species to be discovered in the garnet supergroup. The nomenclature outlined in this report has been approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (Voting Proposal 11-D).

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Spectroscopic studies of spessartine from Brazilian pegmatites

Cited by 10 publications

References 17 publications

Synthesis and crystal chemistry of Fe3+-bearing (Mg,Fe3+)(Si,Fe3+)O3 perovskite

Synthesis and crystal chemistry of Fe3+-bearing (Mg,Fe3+)(Si,Fe3+)O3 perovskite

Formation of large synthetic zincite (ZnO) crystals during production of zinc white

Nomenclature of the garnet supergroup

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