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The high-pressure behavior of wardite, NaAl3(PO4)2(OH)4·2H2O (a = 7.0673(2) &Aring, c = 19.193(9) &Aring, Sp. Gr. P41212), has been investigated by in-situ single-crystal synchrotron diffraction experiments up to 9 GPa, using a diamond anvil cell under quasi-hydrostatic conditions. This phosphate does not experience any pressure-induced phase transition, or anomalous compressional behavior, within the pressure-range investigated: its compressional behavior is fully elastic and all the deformation mechanisms, at the atomic scale, are reversible upon decompression. A second-order Birch&ndash, Murnaghan Equation of State was fitted to the experimental data, weighted by their uncertainty in pressure (P) and volume (V), with the following refined parameters: V0 = 957.8(2) &Aring, 3 and KV0 = &minus, V0( &para, P/&para, V)P0,T0 = 85.8(4) GPa (&beta, V0 = 1/KV0 = 0.01166(5) GPa&minus, 1). Axial bulk moduli were also calculated, with: K0(a) = 98(3) GPa (&beta, 0(a) = 0.0034(1) GPa&minus, 1) and K0(c) = 64(1) GPa (&beta, 0(c) = 0.0052(1) GPa&minus, 1). The anisotropic compressional scheme is: K0(a):K0(c) = 1.53:1. A series of structure refinements were performed on the basis of the intensity data collected in compression and decompression. The mechanisms at the atomic scale, responsible for the structure anisotropy of wardite, are discussed.

A wardite mineral sample from Lavra Da Ilha, Minas Gerais, Brazil has been examined by vibrational spectroscopy. The mineral is unusual in that it belongs to a unique symmetry class, namely the tetragonal-trapezohedral group. The structure of wardite contains layers of corner-linked –OH bridged MO6 octahedra stacked along the tetragonal C-axis in a four-layer sequence and linked by PO4 groups. Consequentially not all phosphate units are identical. Two intense Raman bands observed at 995 and 1051 cm^-1 are assigned to the m1 PO4^3- symmetric stretching mode. Intense Raman bands are observed at 605 and 618 cm^-1 with shoulders at 578 and 589 cm^-1 are assigned to the m4 out of plane bending modes of the PO4^3- . The observation of multiple bands supports the concept of non-equivalent phosphate units in the structure. Sharp infrared bands are observed at 3544 and 3611 cm^-1 are attributed to the OH stretching vibrations of the hydroxyl units. Vibrational spectroscopy enables subtle details of the molecular structure of wardite to be determined.

Vibrational spectroscopy enables subtle details of the molecular structure of minyulite KAl2(OH,F)(PO4)2⋅4(H2O). Single crystals of a pure phase from a Brazilian pegmatite were used. Minyulite belongs to the orthorhombic crystal system. This indicates that it has three axes of unequal length, yet all are perpendicular to each other. The infrared and Raman spectroscopy were applied to compare the structure of minyulite with wardite. The reason for the comparison is that both are Al containing phosphate minerals. The Raman spectrum of minyulite shows an intense band at 1012 cm(-1) assigned to the ν1PO4(3-) symmetric stretching vibrations. A series of low intensity Raman bands at 1047, 1077, 1091 and 1105 cm(-1) are assigned to the ν3PO4(3-) antisymmetric stretching modes. The Raman bands at 1136, 1155, 1176 and 1190 cm(-1) are assigned to AlOH deformation modes. The infrared band at 1014 cm(-1) is ascribed to the PO4(3-) ν1 symmetric stretching vibrational mode. The infrared bands at 1049, 1071, 1091 and 1123 cm(-1) are attributed to the PO4(3-) ν3 antisymmetric stretching vibrations. The infrared bands at 1123, 1146 and 1157 cm(-1) are attributed to AlOH deformation modes. Raman bands at 575, 592, 606 and 628 cm(-1) are assigned to the ν4 out of plane bending modes of the PO4(3-) unit. In the 2600-3800 cm(-1) spectral range, Raman bands for minyulite are found at 3661, 3669 and 3692 cm(-1) are assigned to AlOH/AlF stretching vibrations. Broad infrared bands are also found at 2904, 3105, 3307, 3453 and 3523 cm(-1). Raman bands at 3225, 3324 cm(-1) are assigned to water stretching vibrations. A comparison is made with the vibrational spectra of wardite. Raman spectroscopy complimented with infrared spectroscopy has enabled aspects of the structure of minyulite to be ascertained and compared with that of other phosphate minerals.

Vibrational spectroscopy enables subtle details of the molecular structure of kapundaite to be determined. Single crystals of a pure phase from a Brazilian pegmatite were used. Kapundaite is the Fe 3+ member of the wardite group. The infrared and Raman spectroscopy were applied to compare the structure of kapundaite with wardite. The Raman spectrum of kapundaite in the 800–1400 cm −1 spectral range shows two intense bands at 1089 and 1114 cm −1 assigned to the ν 1 PO 4 3 - symmetric stretching vibrations. The observation of two bands provides evidence for the non-equivalence of the phosphate units in the kapundaite structure. The infrared spectrum of kapundaite in the 500–1300 cm −1 shows much greater complexity than the Raman spectrum. Strong infrared bands are found at 966, 1003 and 1036 cm −1 and are attributed to the ν 1 PO 4 3 - symmetric stretching mode and ν 3 PO 4 3 - antisymmetric stretching mode. Raman bands in the ν 4 out of plane bending modes of the PO 4 3 - unit support the concept of non-equivalent phosphate units in the kapundaite structure. In the 2600–3800 cm −1 spectral range, Raman bands for kapundaite are found at 2905, 3151, 3311, 3449 and 3530 cm −1 . These bands are broad and are assigned to OH stretching vibrations. Broad infrared bands are also found at 2904, 3105, 3307, 3453 and 3523 cm −1 and are attributed to water. Raman spectroscopy complimented with infrared spectroscopy has enabled aspects of the structure of kapundaite to be ascertained and compared with that of other phosphate minerals.

The study of the gossan from Ruffiac, Morbihan (Kosakevitch et al., 1979) afforded the recognition of a rare mineral species, wardite NaAl₃(OH)₄(PO₄)₂ • 2 H₂O. The optical and crystallographic properties are established and an electron microprobe analysis has been performed. This work leads to reinvestigate « soumansite » from Montebras, Creuse (Lacroix, 1910), by X-ray diffraction and by a microprobe analysis, and to discredit definitively the name « soumansite » on behalf of the name wardite which has priority. A short comparison between the two deposit condition in Montebras and in Ruffiac is also given., L'étude du chapeau de fer de Ruffiac, Morbihan (Kosakevitch et al., 1979) a permis l'identification d'un minéral rare, la wardite NaAl₃(OH)₄(PO₄)₂ • 2 H₂O. Les propriétés optiques et cristallographiques sont données. Des analyses ont été effectuées à la microsonde. Ce travail nous a amenés à réexaminer la « soumansite » de Montebras, Creuse (Lacroix, 1910) ; le diagramme de poudre et l'analyse chimique montrent qu'il s'agit en fait d'une wardite. Il convient donc de discréditer définitivement le terme de « soumansite » au profit de celui de wardite qui a priorité. Une brève comparaison entre les conditions de gisement, à Montebras et Ruffiac est faite., Pillard François, Fontan François, Permingeat François. Un nouveau gisement de wardite en France (Ruffiac, Morbihan) et la synonymie « soumansite » = wardite. In: Bulletin de Minéralogie, volume 104, 5, 1981. pp. 681-685.

A mineral found at Rochefort-en-Terre (Morbihan) and formerly identified as cacoxenite is indeed an aluminiferous cyrilovite. A historial review of wardites (without Ca) and cyrilovites is given. All the different mineralogical properties compared with those of cyrilovites and wardites confirm that the mineral is actually a term, intermediate of the possible isomorphic series between cyrilovite and described for the first time. Tetragonal with a = 7.247(2) et c = 19.253(4) Å. The intense powder pattern lines are similar to those of cyrilovites and wardites, however the intermediate values for d permit to distingnish : 4.789(5) ; 3.554(5) ; 3.191(6) ; 3.148(8) ; 3.071(7) ; 2.637(7) Å. Gcalc = 3.052 Gmeas = 2.95 ± 0.05 which is too small because of the microfissuration. Uniaxial negative and slightly pleochroïc ne = 1.725(3) (colourless), n₀ = 1.751(3) (pale lemmon yellow). The electron microprobe analysis yields : P₂O₅ 31.61 ; Fe₂O₃ 38.88 ; Al₂O₃ 7.41 ; Na₂O 6.56 ; K₂O 0.03 ; CaO 0.22 ; H₂O 15.9 (A.T.G.) ; total 100.61 % very close to the theoretical composition Na (Fe₂.₃₁Al₀.₆₉) (OH)₄ (PO₄) ₂ • 2 H₂O with Al/(Al + Fe) = 23 %. The curves of differential and thermogravimetric analysis are given and discussed. This aluminiferous cyrilovite fills (with a grained texture and tending to take a spherolitic form) fractures and voids in dufrenite or cavities in limonitic mass (mainly goethite) formely mined in clays of weathered micaschistes of the Arz valley (Morbihan, Bretagne)., Un minéral de Rochefort-en-Terre (Morbihan), autrefois identifié comme cacoxénite, est en réalité une cyrilovite aluminifère. Un aperçu historique sur les wardites (exemptes de Ca) et les cyrilovites est donné. Les diverses propriétés minéralogiques, comparées à celles des cyrilovites et des wardites, confirment qu'il s'agit effectivement d'un terme, intermédiaire de la série isomorphe possible entre la cyrilovite et la wardite, décrit pour la première fois. Quadratique avec a = 7,247(2) et c = 19,253(4) Å. Les principales raies du diagramme de poudre, analogues à celles des cyrilovites et des wardites, permettent toutefois une distinction par les valeurs intermédiaires de d(Å) : 4,789(10) ; 3,554(5) ; 3,191(6) ; 3,148(8) ; 3,071(7) ; 2,637(7). dx = 3,052 et dmes = 2.95 ± 0,05 trop faible à cause de la microfissuration. Uniaxe négatif et faiblement pléochroïque : ne = 1,725(3) (incolore), n₀ = 1,751(3) (jaune citron pâle). L'analyse à la microsonde électronique fournit : P₂O₅ 31,61 ; Fe₂O₃ 38,88 ; Al₂O₃ 7,41 ; Na₂O 6,56 ; K₂O 0,03 ; CaO 0,22 ; H₂O 15,9 (par ATP) ; total 100,61 %, proche de la composition théorique Na (Fe₂,₃₁Al₀,₆₉) (OH)₄ (PO₄) ₂ • 2 H₂O avec Al : (Al + Fe) = 23 %. Les courbes d'analyses thermiques différentielles et thermopondérales sont données et discutées. La cyrilovite aluminifère présente une texture grenue, tendant à prendre la forme sphérolitique remplissant les fissures et les vacuoles de dufrénite, ou des cavités dans la masse de goethite ou de limonite autrefois exploitées dans les argiles de décomposition superficielle des micaschistes de la vallée de l'Arz (Morbihan, Bretagne)., Fontan François, Permingeat François, Pillard François. Une cyrilovite aluminifère, premier jalon d'une possible série de solutions solides entre la cyrilovite et la wardite. In: Bulletin de Minéralogie, volume 104, 6, 1981. 26e congrès géologique international – Paris – Juillet 1980. Section Minéralogie. Section Pétrographie : symposium « Interactions fluides, minéraux, roches ».

The infrared spectra of five analyzed samples of cyrilovite and wardite have been registered in the 4000-300 cm-1 region and are discussed in connection with the structure and the chemical composition of these minerals. The O-H stretching frequencies are distributed into two spectral regions : two very broad bands near 2950 and 3300 cm-1 which are due to water molecules engaged in short hydrogen bonds ; and two very sharp and strong peaks (3550 and 3495 cm-1 for pure cyrilovite ; 3621 an 3555 cm-1 for pure wardite) due to the stretch of hydroxyl groups. The spectrum of aluminous cyrilovite exhibits two additional bands, whose intensities depend on the percentage of Fe/Al replacement. Thus, the frequency pattern in the 3650-3450 cm-1 region allows an easy discrimination between pure cyrilovite, pure wardite and aluminous cyrilovite. The vibrations of the (PO4) ion are more or less modified by the nature of the trivalent cation (Al or Fe) and accordingly, the low- and medium-frequency spectrum (below 1400 cm-1) is fair complex, and no detailed interpretation is available., Les spectres infrarouges de cinq échantillons analysés de cyrilovite et de wardite ont été enregistrés entre 4000 et 300 cm-1 et sont discutés en fonction de la structure et de la composition chimique de ces minéraux. Les fréquences de valence O-H sont réparties en deux groupes : deux bandes très larges vers 2950 et 3300 cm-1 dues aux molécules d'eau engagées dans des ponts hydrogène courts ; deux bandes fines et intenses (3550 et 3945 cm-1 pour la cyrilovite pure ; 3621 et 3555 cm-1 pour la wardite pure) dues aux vibrations des groupes hydroxyle. Il apparaît en outre, pour les cyrilovites aluminifères, deux bandes supplémentaires dont les intensités dépendent du taux de remplacement Fe/Al. La distribution des fréquences dans le domaine 3650-3450 cm-1 permet de faire immédiatement la distinction entre une cyrilovite pure, une wardite pure et une cyrilovite aluminifère. Les vibrations de l'ion (PO4) sont plus ou moins fortement altérées par la nature du cation trivalent (Fe ou Al) ; il s'ensuit que le spectre de basse et moyenne fréquence (en dessous de 1400 cm-1) est relativement complexe et ne peut être interprété de manière détaillée., Tarte Pierre, Fransolet André-Mathieu, Pillard François. Le spectre infrarouge de la cyrilovite et de la wardite : corrélations entre la structure et la composition chimique. In: Bulletin de Minéralogie, volume 107, 6, 1984. pp. 745-754.