Identification of montgomeryite mineral [Ca4MgAl4(PO4)6.(OH)4•12H2O] found in the Jenolan Caves - Australia

In this paper, we report on many phosphate containing natural minerals found in the Jenolan Caves - Australia. Such minerals are formed by the reaction of bat guano and clays from the caves. Among these cave minerals is the montgomeryite mineral [Ca4MgAl4(PO4)6.(OH)4.12H2O]. The presence of montgomeryite in deposits of the Jenolan Caves - Australia has been identified by X-ray diffraction (XRD). Raman spectroscopy complimented with infrared spectroscopy has been used to characterize the crystal structure of montgomeryite. The Raman spectrum of a standard montgomeryite mineral is identical to that of the Jenolan Caves sample. Bands are assigned to H2PO4-, OH and NH stretching vibrations. By using a combination of XRD and Raman spectroscopy, the existence of montgomeryite in the Jenolan Caves - Australia has been proven. A mechanism for the formation of montgomeryite is proposed.

Raman spectroscopy of synthetic CaHPO4•2H2O– and in comparison with the cave mineral brushite

The mineral brushite has been synthesised by mixing calcium ions and hydrogen phosphate anions to mimic the reactions in a Cave. The vibrational spectra of the synthesised brushite were compared with that of the natural Cave mineral. Bands attributable to the PO43- and HPO42- anions are observed. Brushite, both synthetic and natural, is characterised by an intense sharp band at 985 cm-1 with a shoulder at 1000 cm-1. Characteristic bending modes are observed in the 300 to 600 cm-1 region. The spectra of the synthesised brushite matches very well the spectrum of brushite from the Moorba Cave, Western Australia.

Vibrational spectroscopic study of multianion mineral clinotyrolite Ca2Cu9[(As,S)O4]4(OH)10•10(H2O)

The molecular structure of the mixed anion mineral Clinotyrolite Ca2Cu9[(As,S)O4]4(OH)10•10(H2O) has been determined by the combination of Raman and infrared spectroscopy. Characteristic bands associated with arsenate, sulphate and hydroxyl units are identified. Broad bands in the OH stretching region are observed and are resolved into component bands. Estimates of hydrogen bond distances were made using a Libowitzky function and both short and long hydrogen bonds are identified. Two intense Raman bands at 842 and ~796 cm-1 are assigned to the ν1 (AsO4)3- symmetric stretching and ν3 (AsO4)3- antisymmetric stretching modes. The comparatively sharp Raman band at 980 cm-1 is assigned to the ν1 (SO4)2- symmetric stretching mode and a broad Raman spectral profile centred upon 1100 cm-1 is attributed to the ν3 (SO4)2- antisymmetric stretching mode.

Vibrational spectroscopic study of the copper silicate mineral ajoite (K,Na)Cu7AlSi9O24(OH)6•3H2O

Ajoite (K,Na)Cu7AlSi9O24(OH)6•3H2O is a mineral named after the Ajo district of Arizona. Raman and infrared spectroscopy were used to characterise the molecular structure of ajoite. The structure of the mineral shows disorder which is reflected in the difficulty of obtaining quality Raman spectra. The Raman spectrum is characterised by a broad spectral profile with a band at 1048 cm-1 assigned to the ν1 (A1g) symmetric stretching vibration. Strong bands at 962, 1015 and 1139 cm-1 are assigned to the ν3 SiO4 antisymmetric stretching vibrations. Multiple ν4 SiO4 vibrational modes indicate strong distortion of the SiO4 tetrahedra. Multiple AlO and CuO stretching bands are observed. Raman spectroscopy and confirmed by infrared spectroscopy clearly shows that hydroxyl units are involved in the ajoite structure. Based upon the infrared spectra, water is involved in the ajoite structure, probably as zeolitic water.

Raman spectroscopy of the borate mineral ameghinite NaB3O3(OH)4

The molecular structure of the sodium borate mineral ameghinite NaB3O3(OH)4 has been determined by the use of vibrational spectroscopy. The crystal structure consists of isolated [B3O3(OH)4]- units formed by one tetrahedron and two triangles. H bonds and Na atoms link these polyanions to form a 3-dimensional framework. The Raman spectrum is dominated by an intense band at 1027 cm-1, attributed to BO stretching vibrations of both the trigonal and tetrahedral boron. A series of Raman bands at 1213, 1245 and 1281cm-1 are ascribed to BOH in-plane bending modes. The infrared spectra are characterized by strong overlap of broad multiple bands. An intense Raman band found at 620 cm-1 is attributed to the bending modes of trigonal and tetrahedral boron. Multiple Raman bands in the OH stretching region are observed at 3206, 3249 and 3385 cm-1. Raman spectroscopy coupled with infrared spectroscopy has enabled aspects about the molecular structure of the borate mineral ameghinite to be assessed.

Vibrational spectroscopic study of the mineral creaseyite Cu2Pb2(Fe,Al)2(Si5O17)·6H2O – a zeolite mineral?

Vibrational spectroscopy has been used to characterise the mineral creaseyite Cu2Pb2(Fe,Al)2(Si5O17)·6H2O. The mineral is found in the oxidised zone of base metal deposits and interestingly is associated with copper silicate minerals including ajoite, kinoite, chrysocolla as well as wulfenite, willemite, mimetite and wickenburgite. Creaseyite is a mineral with zeolitic properties. A Raman band at 998 cm−1 is assigned to the SiO stretching vibration of SiO3 units. The Raman band at 1071 cm−1 is assigned to the SiO stretching vibrations of the Si2O5 units. Raman bands are found at 2750, 2902, 3162, 3470 and 3525 cm−1. The band at 3525 cm−1 is attributed to zeolitic water. Other bands are assigned to water coordinated to the metal cations. Vibrational spectroscopy enables aspects of the molecular structure of creaseyite to be determined.

The influence of vegetation and soil type on the speciation of iron in soil water

Soluble organic matter derived from exotic Pinus species has been shown to form stronger complexes with iron (Fe) than that derived from most native Australian species. It has also been proposed that the establishment of exotic Pinus plantations in coastal southeast Queensland may have enhanced the solubility of Fe in soils by increasing the amount of organically complexed Fe, but this remains inconclusive. In this study we test whether the concentration and speciation of Fe in soil water from Pinus plantations differs significantly from soil water from native vegetation areas. Both Fe redox speciation and the interaction between Fe and dissolved organic matter (DOM) were considered; Fe - DOM interaction was assessed using the Stockholm Humic Model. Iron concentrations (mainly Fe 2+) were greatest in the soil waters with the greatest DOM content collected from sandy podosols (Podzols), where they are largely controlled by redox potential. Iron concentrations were small in soil waters from clay and iron oxide-rich soils, in spite of similar redox potentials. This condition is related to stronger sorption on to the reactive clay and iron oxide mineral surfaces in these soils, which reduces the amount of DOM available for electron shuttling and microbial metabolism, restricting reductive dissolution of Fe. Vegetation type had no significant influence on the concentration and speciation of iron in soil waters, although DOM from Pinus sites had greater acidic functional group site densities than DOM from native vegetation sites. This is because Fe is mainly in the ferrous form, even in samples from the relatively well-drained podosols. However, modelling suggests that Pinus DOM can significantly increase the amount of truly dissolved ferric iron remaining in solution in oxic conditions. Therefore, the input of ferrous iron together with Pinus DOM to surface waters may reduce precipitation of hydrous ferric oxides (ferrihydrite) and increase the flux of dissolved Fe out of the catchment. Such inputs of iron are most probably derived from podosols planted with Pinus.

Molecular structure of the mineral svanbergite SrAl3(PO 4,SO4)2(OH)6 - A vibrational spectroscopic study

The mineral svanbergite SrAl 3(PO 4,SO 4) 2(OH) 6 is a hydroxy phosphate-sulphate mineral belonging to the beudantite subgroup of alunites and has been characterised by vibrational spectroscopy. Bands at various wavenumbers were assigned to the different vibrational modes of svanbergite, which were then associated with the structure of the mineral. Bands were primarily assigned to phosphate and sulphate stretching and bending modes. Two symmetric stretching modes for both phosphate and sulphate supported the concept of non-equivalent phosphate and sulphate units in the mineral structure. Bands in the OH stretching region enabled hydrogen bond distances to be calculated. Comparison of the hydrogen bond distances and the calculated hydrogen bond distances from the structure models indicates that hydrogen bonding in svanbergite occurs between the two OH units rather than OH to SO42- units.

Raman spectroscopic study of the mineral xonotlite Ca 6Si 6O 17(OH) 2-A component of plaster boards

The mineral xonotlite Ca 6Si 6O 17(OH) 2 is a crystalline calcium silicate hydrate which is widely used in plaster boards and in many industrial applications. The structure of xonotlite is best described as having a dreierdoppelketten silicate structure, and describes the repeating silicate trimer which forms the silicate chains, and doppel indicating that two chains combine. Raman bands at 1042 and 1070 cm -1 are assigned to the SiO stretching vibrations of linked units of Si 4O 11 units. Raman bands at 961 and 980 cm -1 serve to identify Si 3O 10 units. The broad Raman band at 862 cm -1 is attributed to hydroxyl deformation modes. Intense Raman bands at 593 and 695 cm -1 are assigned to OSiO bending vibrations. Intense Raman bands at 3578, 3611, 3627 and 3665 cm -1 are assigned to OH stretching vibrations of the OH units in xonotlite. Infrared spectra are in harmony with the Raman spectra. Raman spectroscopy with complimentary infrared spectroscopy enables the characterisation of the building material xonotlite.

Vibrational spectroscopy of the multianion mineral kemmlitzite (Sr,Ce)Al3(AsO4)(SO4)(OH)6

Some minerals are colloidal and show no X-ray diffraction patterns. Vibrational spectroscopy offers one of the few methods for the assessment of the structure of these types of mineral. Among this group of minerals is kemmlitzite (Sr,Ce)Al3(AsO4)(SO4)(OH)6. The objective of this research is to determine the molecular structure of the mineral kemmlitzite using vibrational spectroscopy. Raman microscopy offers a useful method for the analysis of such colloidal minerals. Raman and infrared bands are attributed to the AsO43- , SO42- and water stretching vibrations. The Raman spectrum is dominated by a very intense sharp band at 984 cm-1 assigned to the SO42- symmetric stretching mode. Raman bands at 690, 772 and 825 cm-1 may be assigned to the AsO43- antisymmetric and symmetric stretching modes. Raman bands observed at 432 and 465 cm-1 are attributable to the doubly degenerate 2 (SO4)2- bending mode. Vibrational spectroscopy is important in the assessment of the molecular structure of the kemmlitzite, especially when the mineral is non-diffracting or poorly diffracting.

Transmission X-ray microscopy : a new tool in clay mineral floccules characterization

Effective flocculation and dewatering of mineral processing streams containing clays are microstructure dependent in clay-water systems. Initial clay flocculation is crucial in the design and for the development of a new methodology of gas exploitation. Microstructural engineering of clay aggregates using covalent cations and Keggin macromolecules have been monitored using the new state of the art Transmission X-ray Microscope (TXM) with 60 nm tomography resolution installed in a Taiwanese synchrotron. The 3-D reconstructions from TXM images show complex aggregation structures in montmorillonite aqueous suspensions after treatment with Na+, Ca2+ and Al13 Keggin macromolecules. Na-montmorillonite displays elongated, parallel, well-orientated and closed-void cellular networks, 0.5–3 μm in diameter. After treatment by covalent cations, the coagulated structure displays much smaller, randomly orientated and openly connected cells, 300–600 nm in diameter. The average distances measured between montmorillonite sheets was around 450 nm, which is less than half of the cell dimension measured in Na-montmorillonite. The most dramatic structural changes were observed after treatment by Al13 Keggin; aggregates then became arranged in compacted domains of a 300 nm average diameter composed of thick face-to-face oriented sheets, which forms porous aggregates with larger intra-aggregate open and connected voids.

Assessment of the molecular structure of the borate mineral sakhaite Ca12Mg4(BO3)7(CO3)4Cl(OH)2·H2O using vibrational spectroscopy

The structure of the borate mineral sakhaite Ca12Mg4(BO3)7(CO3)4Cl(OH)2·H2O, a borate–carbonate of calcium and magnesium has been assessed using vibrational spectroscopy. Assignment of bands is undertaken by comparison with the data from other published results. Intense Raman band at 1134 cm−1 with a shoulder at 1123 cm−1 is assigned to the symmetric stretching mode. The Raman spectrum displays bands at 1479, 1524 and 1560 cm−1 which are assigned to the antisymmetric stretching vibrations. The observation of multiple carbonate stretching bands supports the concept that the carbonate units are non-equivalent. The Raman band at 968 cm−1 with a shoulder at 950 cm−1 is assigned to the symmetric stretching mode of trigonal boron. Raman bands at 627 and 651 cm−1 are assigned to the out-of-plane bending modes of trigonal and tetrahedral boron. Raman spectroscopy coupled with infrared spectroscopy enables the molecular structure of the mineral sakhaite to be assessed.

The borate mineral jeremejevite Al6(BO3)5(F,OH)3 – A vibrational spectroscopic study

Jeremejevite is a borate mineral of aluminium and is of variable colour, making the mineral and important inexpensive jewel. The mineral contains variable amounts of F and OH, depending on origin. A comparison of the vibrational spectroscopic data is made with the published data of borate minerals. Raman spectra were averaged over a range of crystal orientations. Two intense Raman bands observed at 961 and 1067 cm−1 are assigned to the symmetric stretching and antisymmetric stretching modes of trigonal boron. Infrared spectrum, bands observed at 1229, 1304, 1350, 1388 and 1448 cm−1 are attributed to BOH in-plane bending modes. Intense Raman band found at 372 cm−1 with other bands of significant intensity at 327 and 417 cm−1 is assigned to trigonal borate bending modes. A quite intense Raman band is found at 3673 cm−1 with other sharp Raman bands found at 3521, 3625 and 3703 cm−1 are assigned to the stretching modes of OH. Raman and infrared spectroscopy has been used to assess the molecular structure of the mineral jeremejevite. Such research is important in the study of borate based nanomaterials.

Assessment of the molecular structure of the borate mineral boracite Mg3B7O13Cl using vibrational spectroscopy

Boracite is a magnesium borate mineral with formula: Mg3B7O13Cl and occurs as blue green, colorless, gray, yellow to white crystals in the orthorhombic – pyramidal crystal system. An intense Raman band at 1009 cm−1 was assigned to the BO stretching vibration of the B7O13 units. Raman bands at 1121, 1136, 1143 cm−1 are attributed to the in-plane bending vibrations of trigonal boron. Four sharp Raman bands observed at 415, 494, 621 and 671 cm−1 are simply defined as trigonal and tetrahedral borate bending modes. The Raman spectrum clearly shows intense Raman bands at 3405 and 3494 cm−1, thus indicating that some Cl anions have been replaced with OH units. The molecular structure of a natural boracite has been assessed by using vibrational spectroscopy.