Gonnardite; re-examination of holotype material and discreditation of tetranatrolite

Artioli, Gilberto; Galli, Ermanno

doi:10.2138/am-1999-0924

Cited by 32 publications

(17 citation statements)

References 14 publications

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“…Considering only the unit-cell parameters (a ~ 13.08, b ~ 13.06, c ~ 6.6 Å), one would be driven to ascribe the crystal to gonnardite (or tetranatrolite) (a ~ b ~ 13.1, c ~ 6.6 Å; Mazzi et al 1986;Ross et al 1992;Artioli and Galli 1999;Evans et al 2000). Furthermore, the chemical analysis does not always provide a unique answer, because of the extensive variation in Na/Ca and Si/Al ratios in thomsonite toward chemical compositions close to that of gonnardite (Ross et al 1992).…”

Section: Discussionmentioning

confidence: 99%

“…Despite the very small dimensions of the crystals, consistent chemical analyses (obtained by averaging 6 point analyses and calculated on the basis of 80 O atom) were obtained. The chemical formula of one of the two crystals was Na 7.54 Ca 5.37 [Al 17.15 Si 22.56 ] Σ=39.71 O 80 ·26.2H 2 O, which would be considered gonnardite (or tetranatrolite) rather than thomsonite (with a ~ b ~ 13.1 and c ~ 6.6 Å; Mazzi et al 1986;Ross et al 1992;Artioli and Galli 1999;Evans et al 2000). For the other small crystal, the resultant chemical formula was K 0.03 Na 4.33 Ca 5.85 Mg 0.52 [Al 16.81 Si 23.12 ] Σ=39.93 O 80 ·23.6H 2 O, which could be considered as Ca-poor thomsonite.…”

Section: Experimental Methodsmentioning

confidence: 99%

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Crystal structure and low-temperature behavior of "disordered" thomsonite

Gatta

Kahlenberg

Kaindl

et al. 2010

American Mineralogist

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The crystal structure, crystal chemistry, and low-temperature structural evolution of natural thomsonite from Terzigno, Somma-Vesuvius volcanic complex, Naples Province, Italy, have been investigated by means of in situ single-crystal X-ray diffraction, electron microprobe analysis in the wavelength dispersive mode, and Raman spectroscopy. Six structure refinements have been obtained at different temperatures: 295.5, 248.0, 198.0, 148.0, 98.0, and 296.0 K (after the low-T experiments). The reflection conditions and the structure refinements prove that the crystal of thomsonite here investigated is orthorhombic with a = 13.0809(3), b = 13.0597 (3), c = 6.6051(1) Å, V = 1128.37 (14) Å 3 , and space group Pbmn, which differs from thomsonite from different localities reported in previous studies (with a ~ 13.1, b ~ 13.06, c ~ 13.2 Å, and space group Pncn). The refined bond distances suggest that the Si/Al-distribution in the tetrahedral framework is fully "disordered," giving rise to the halving of the c axis relative to that found in "ordered" thomsonites. The extra-framework population consists of: (1) one site about 50% occupied by Ca (labeled as "Ca"); (2) one site occupied by Na (~70%) and Ca (~30%) (labeled as "Na"); and (3) three water molecule sites ("W1," "W2," "W3"). The structure refinements allowed the location of all the proton sites, and the hydrogen-bonding scheme in the structure is provided. The low-temperature refinements show no significant change in the structure within the T-range investigated. The evolution of the unit-cell volume with T exhibits a continuous and linear trend, without any evident thermo-elastic anomaly, with thermal expansion coefficients α V = V -1 ⋅∂V/∂T= 20(2)·10 -6 K -1 (between 98.0 and 295.5 K). A list with the principal Raman active modes is provided and a comparison with the vibrational modes previously found for "ordered" thomsonite is carried out.

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Section: Discussionmentioning

confidence: 99%

Section: Experimental Methodsmentioning

confidence: 99%

Crystal structure and low-temperature behavior of "disordered" thomsonite

Gatta

Kahlenberg

Kaindl

et al. 2010

American Mineralogist

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“…The positions of their anhydrous residues in the NaO 0.5 -CaO-AlO 1.5 -SiO 2 composition pyramid (Fig. 2) show clearly that the gonnardite studied by Mazzi et al [22] is close in composition to tetranatrolite [20] and that the composition analyzed by Artioli and Galli [23] is close to the ideal composition of gonnardite. Thus, tetranatrolite and gonnardite are the same solid-solution phase with a rather broad homogeneity region.…”

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confidence: 60%

“…Compositions of the anhydrous residues of natrolite-thomsonite zeolites in the NaO 0.5 -CaO-AlO 1.5 -SiO 2 pyramid; the cubes and spheres represent the nominal and reported compositions; the exact chemical compositions are given in Table 2. KOL'TSOVA Tetranatrolite was first found in 1969 in hydrothermal veins of the Ilimaussaq alkaline complex, Greenland, in the form of prism-shaped crystals [16] and then in Canada in the form of epitactic overgrowths on natrolite [17]. After gonnardite and tetranatrolite were shown to crystallize in tetragonal symmetry with almost identical lattice parameters [16][17][18][19][20][21][22][23] and to have the same structure, there was a great deal of controversy as to whether these are two different minerals or the same mineral [20,23,24]. The positions of their anhydrous residues in the NaO 0.5 -CaO-AlO 1.5 -SiO 2 composition pyramid (Fig.…”

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confidence: 99%

Zeolites of the Natrolite-Thomsonite Series

Kol’tsova

2005

Inorg Mater

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“…Morphological and X-ray diffraction analyses cannot discriminate between natrolite and tetranatrolite, which has also been recently discredited by the Subcommittee on Zeolite Mineral Nomenclature of the IMA Committee on NEW Minerals and Mineral Names (Coombs et al, 1997;Artioli & Galli, 1999): discrimination may be done only by means of chemical and single crystal diffraction analyses. During the present study several pseudo-tetragonal vitreous, perfectly transparent crystals have been selected from fragments of the stalactites as well as from fragment of rock of the walls of the Kitum Cave.…”

Section: Discussionmentioning

confidence: 99%

Untitled

2003

IJS

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Kenya is one of the few countries in which karst cavities are scarce with respect to volcanic ones, which are widespread throughout the whole country. The great variability in lava composition allowed the evolution of very different cavities, some of which are amongst the largest lava tubes of the world.As normal for such a kind of cave, the hosted speleothems and cave minerals are scarce but important from the minerogenetic point of view. Anyway up to present no specific mineralogical research have been carried out therein. During the 8th International Symposium on Volcanospeleology, held in Nairobi in February 1998, some of the most important volcanic caves of Kenya have been visited and their speleothems and/or chemical deposits sampled: most of them were related to thick guano deposits once present inside these cavities. Speleothems mainly consisted of opal or gypsum, while the deposits related to guano often resulted in a mixture of sulphates and phosphates. The analyses confirmed the great variability in the minerogenetic mechanisms active inside the volcanic caves, which consequently allow the evolution of several different minerals even if the total amount of chemical deposit is scarce. Among the observed minerals kogarkoite, phillipsite and hydroxyapophyllite, must be cited because they are new cave minerals not only for the lava tubes of Kenya, but also for the world cave environment. The achieved results are compared with the available random data from previous literature in order to allow an updated overview on the secondary cave minerals of Kenya. Keywords: Volcanic caves, Cave minerals, Kenya RIASSUNTOIl Kenya è una delle poche nazioni al mondo in cui le cavità carsiche sono molto meno di quelle vulcaniche, che invece sono comuni e distribuite su tutto il suo territorio. La grande variabilità nella composizione delle rocce effusive dell'area ha permesso l'evoluzione di grotte vulcaniche molto differenti tra loro, alcune delle quali sono tra le grotte laviche più grandi del mondo.Come già osservato in precedenza anche queste cavità ospitano pochi e piccoli speleotemi che, però, sono molto importanti dal punto di vista delle mineralizzazioni secondarie di grotta. Nonostante ciò sino ad oggi non era stata fatta alcuna ricerca mineralogica sistematica all'interno di queste cavità. Durante l' VIII Simposio Internazionale di Vulcanospeleologia, tenutosi a Nairobi nel febbraio del 1998, è stato possibile visitare alcune delle più importanti grotte vulcaniche del Kenya. All'interno di tali cavità sono stati campionati speleotemi e depositi chimici secondari, alcuni dei quali legati all'abbondante quantità di guano un tempo presente al loro interno.I risultati delle analisi hanno confermato la grande variabilità di meccanismi minerogenetici attivi all'interno delle grotte vulcaniche, che si riflettono, di conseguenza, in una notevole varietà di specie mineralogiche presenti, anche se nel loro insieme i depositi chimici secondari risultano spesso essere di quantità e dimensioni piuttosto scarse. Tra...

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Gonnardite; re-examination of holotype material and discreditation of tetranatrolite

Cited by 32 publications

References 14 publications

Crystal structure and low-temperature behavior of "disordered" thomsonite

Crystal structure and low-temperature behavior of "disordered" thomsonite

Zeolites of the Natrolite-Thomsonite Series

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