Raman spectroscopy of the multi-anion mineral mallestigite Pb3Sb5+(SO4)(AsO4)(OH)6•3H2O – a mineral of archaeological significance

Some minerals are formed which show poorly defined X-ray diffraction patterns. Vibrational spectroscopy offers one of the few methods for the assessment of the structure of the oxyanions in such minerals. Among this group of minerals is mallestigite with formula Pb3Sb5+(SO4)(AsO4)(OH)6•3H2O. The objective of this research is to determine the molecular structure of the mineral mallestigite using vibrational spectroscopy. Raman and infrared bands are attributed to the AsO43- , SO42- and water stretching vibrations. Mallestigite is a mineral formed in ancient waste dumps such as occurs at Mallestiger, Carinthia, Austria and as such is a mineral of archaeological significance.

Vibrational spectroscopy of synthetic stercorite H(NH4)Na(PO4)•4H2O – a comparison with the natural cave mineral

In order to mimic the chemical reactions in cave systems, the analogue of the mineral stercorite H(NH4)Na(PO4)•4H2O has been synthesised. X-ray diffraction of the stercorite analogue matches the stercorite reference pattern. A comparison is made with the vibrational spectra of synthetic stercorite analogue and the natural Cave mineral. The mineral in nature is formed by the reaction of bat guano chemicals on calcite substrates. A single Raman band at 920 cm-1 (Cave) and 922 cm-1 (synthesised) defines the presence of hydrogen phosphate in the mineral. In the synthetic stercorite analogue, additional bands are observed and are attributed to the dihydrogen and phosphate anions. The vibrational spectra of synthetic stercorite only partly match that of the natural stercorite. It is suggested that natural stercorite is more pure than that of synthesised stercorite. Antisymmetric stretching bands are observed in the infrared spectrum at 1052, 1097, 1135 and 1173 cm-1. Raman spectroscopy shows the stercorite mineral is based upon the hydrogen phosphate anion and not the phosphate anion. Raman and infrared bands are found and assigned to PO43-, H2O, OH and NH stretching vibrations. Raman spectroscopy shows the synthetic analogue is similar to the natural mineral. A mechanism for the formation of stercorite is provided.

The molecular structure of the multianion mineral hidalgoite PbAl3(AsO4)(SO4)(OH)6 : implications for arsenic removal from soils

The objective of this research is to determine the molecular structure of the mineral hidalgoite PbAl3(AsO4)(SO4)(OH)6 using vibrational spectroscopy. The mineral is found in old mine sites. Observed bands are assigned to the stretching and bending vibrations of (SO4)2- and (AsO4)3- units, stretching and bending vibrations of hydrogen bonded (OH)- ions and Al3+-(O,OH) units. The approximate range of O-H...O hydrogen bond lengths is inferred from the Raman and infrared spectra. Values of 2.6989 Å, 2.7682 Å, 2.8659 Å were obtained. The formation of hidalgoite may offer a mechanism for the removal of arsenic from the environment.

Molecular structural studies of the amorphous mineral pitticite Fe, AsO4, SO4, H2O

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 pitticite simply described as Fe, AsO4, SO4, H2O. The objective of this research is to determine the molecular structure of the mineral pitticite using vibrational spectroscopy. Raman microscopy offers a useful method for the analysis of such colloidal minerals. Raman and infrared bands are attributed to the , and water stretching vibrations. The Raman spectrum is dominated by a very intense sharp band at 983 cm−1 assigned to the symmetric stretching mode. A strong Raman band at 1041 cm−1 is observed and is assigned to the antisymmetric stretching mode. Low intensity Raman bands at 757 and 808 cm−1 may be assigned to the antisymmetric and symmetric stretching modes. Raman bands observed at 432 and 465 cm−1 are attributable to the doubly degenerate ν2(SO4)2- bending mode.

Underwater emissions from a two-stroke outboard engine : a comparison between an EAL and an equivalent mineral lubricant

The emissions to water from a 1.9 kW two-stroke outboard engine were investigated in the laboratory and in the field, with the primary objective being to characterise and quantify the pollutants that remain within the water column. The emission rates of polycyclic aromatic hydrocarbons (PAHs) and volatile organic compounds (VOCs) were determined for the engine when using a mineral and an equivalent environmentally adapted lubricant (EAL). A comparison of the emission rates was conducted between the results from the fresh and sea water tests. The results showed that there was little difference in the emission rates of these pollutants when either of the lubricants was used in both the fresh and sea water. A further set of tests were done to find out the effect on pH of water due to the underwater emissions and these tests were done using both mineral and environmentally adapted lubricant. The results showed that the type of lubricant does not have any effect on the change in pH of the water.

Controls on iron in soils and soil waters of a forested, coastal catchment in subtropical Australia

Soluble organic matter derived from exotic Pinus vegetation forms stronger complexes with iron (Fe) than the soluble organic matter derived from most native Australian species. This has lead to concern about the environmental impacts related to the establishment of extensive exotic Pinus plantations in coastal southeast Queensland, Australia. It has been suggested that the Pinus plantations may enhance the solubility of Fe in soils by increasing the amount of organically complexed Fe. While this remains inconclusive, the environmental impacts of an increased flux of dissolved, organically complexed Fe from soils to the fluvial system and then to sensitive coastal ecosystems are potentially damaging. Previous work investigated a small number of samples, was largely laboratory based and had limited application to field conditions. These assessments lacked field-based studies, including the comparison of the soil water chemistry of sites associated with Pinus vegetation and undisturbed native vegetation. In addition, the main controls on the distribution and mobilisation of Fe in soils of this subtropical coastal region have not been determined. This information is required in order to better understand the relative significance of any Pinus enhanced solubility of Fe. The main aim of this thesis is to determine the controls on Fe distribution and mobilisation in soils and soil waters of a representative coastal catchment in southeast Queensland (Poona Creek catchment, Fraser Coast) and to test the effect of Pinus vegetation on the solubility and speciation of Fe. The thesis is structured around three individual papers. The first paper identifies the main processes responsible for the distribution and mobilisation of labile Fe in the study area and takes a catchment scale approach. Physicochemical attributes of 120 soil samples distributed throughout the catchment are analysed, and a new multivariate data analysis approach (Kohonen’s self organising maps) is used to identify the conditions associated with high labile Fe. The second paper establishes whether Fe nodules play a major role as an iron source in the catchment, by determining the genetic mechanism responsible for their formation. The nodules are a major pool of Fe in much of the region and previous studies have implied that they may be involved in redox-controlled mobilisation and redistribution of Fe. This is achieved by combining a detailed study of a ferric soil profile (morphology, mineralogy and micromorphology) with the distribution of Fe nodules on a catchment scale. The third component of the thesis tests whether the concentration and speciation of Fe in soil solutions from Pinus plantations differs significantly from native vegetation soil solutions. Microlysimeters are employed to collect unaltered, in situ soil water samples. The redox speciation of Fe is determined spectrophotometrically and the interaction between Fe and dissolved organic matter (DOM) is modelled with the Stockholm Humic Model. The thesis provides a better understanding of the controls on the distribution, concentration and speciation of Fe in the soils and soil waters of southeast Queensland. Reductive dissolution is the main mechanism by which mobilisation of Fe occurs in the study area. Labile Fe concentrations are low overall, particularly in the sandy soils of the coastal plain. However, high labile Fe is common in seasonally waterlogged and clay-rich soils which are exposed to fluctuating redox conditions and in organic-rich soils adjacent to streams. Clay-rich soils are most common in the upper parts of the catchment. Fe nodules were shown to have a negligible role in the redistribution of dissolved iron in the catchment. They are formed by the erosion, colluvial transport and chemical weathering of iron-rich sandstones. The ferric horizons, in which nodules are commonly concentrated, subsequently form through differential biological mixing of the soil. Whereas dissolution/ reprecipitation of the Fe cements is an important component of nodule formation, mobilised Fe reprecipitates locally. Dissolved Fe in the soil waters is almost entirely in the ferrous form. Vegetation type does not affect the concentration and speciation of Fe in soil waters, although Pinus DOM has greater acidic functional group site densities than DOM from native vegetation. Iron concentrations are highest in the high DOM soil waters collected from sandy podosols, where they are controlled by redox potential. Iron concentrations are low in soil solutions from clay and iron oxide rich soils, in spite of similar redox potentials. This is related to stronger sorption to the reactive clay and iron oxide mineral surfaces in these soils, which reduces the amount of DOM available for microbial metabolisation and reductive dissolution of Fe. Modelling suggests that Pinus DOM can significantly increase the amount of truly dissolved ferric iron remaining in solution in oxidising conditions. Thus, inputs of ferrous iron together with Pinus DOM to surface waters may reduce precipitation of hydrous ferric oxides and increase the flux of dissolved iron out of the catchment. Such inputs are most likely from the lower catchment, where podosols planted with Pinus are most widely distributed. Significant outcomes other than the main aims were also achieved. It is shown that mobilisation of Fe in podosols can occur as dissolved Fe(II) rather than as Fe(III)-organic complexes. This has implications for the large body of work which assumes that Fe(II) plays a minor role. Also, the first paper demonstrates that a data analysis approach based on Kohonen’s self organising maps can facilitate the interpretation of complex datasets and can help identify geochemical processes operating on a catchment scale.

Raman spectroscopy of the multi-anion mineral schlossmacherite (H3O,Ca)Al3(AsO4,PO4,SO4)2(OH)6

The mineral schlossmacherite (H3O,Ca)Al3(AsO4,PO4,SO4)2(OH)6 , a multi-cation-multi-anion mineral of the beudantite mineral subgroup has been characterised by Raman spectroscopy. The mineral and related minerals functions as a heavy metal collector and is often amorphous or poorly crystalline, such that XRD identification is difficult. The Raman spectra are dominated by an intense band at 864 cm-1, assigned to the symmetric stretching mode of the AsO43- anion. Raman bands at 809 and 819 cm-1 are assigned to the antisymmetric stretching mode of AsO43- . The sulphate anion is characterised by bands at 1000 cm-1 (ν1), and at 1031, 1082 and 1139 cm-1 (ν3). Two sets of bands in the OH stretching region are observed: firstly between 2800 and 3000 cm-1 with bands observed at 2850, 2868, 2918 cm-1 and secondly between 3300 and 3600 with bands observed at 3363, 3382, 3410, 3449 and 3537 cm-1. These bands enabled the calculation of hydrogen bond distances and show a wide range of H-bond distances.

Raman spectroscopic study of the mineral shattuckite Cu5(SiO3)4(OH)2

Shattuckite Cu5(SiO3)4(OH)2 is a copper hydroxy silicate and is commonly known as a ‘healing’ mineral. Three shattuckite mineral samples from three different origins were analysed by Raman spectroscopy. Some Raman bands are common in the spectra of the minerals. Raman bands at around 890, 1058 and 1102 are described as the ν3 –SiO3 antisymmetric stretching vibrations. The Raman band at 670 cm-1 is assigned to the ν4 bending modes of the -SiO3 units and the band at around 785 cm-1is due to Si-O-Si chain stretching mode. Raman (and infrared) spectroscopy proves that water is in the molecular structure of shattuckite; thus the formula is better written as Cu5(SiO3)4(OH)2•xH2O.

Vibrational spectroscopic study of the copper silicate mineral kinoite Ca2Cu2Si3O10(OH)4

Kinoite Ca2Cu2Si3O10(OH)4 is a mineral named after a Jesuit missionary. Raman and infrared spectroscopy have been used to characterise the structure of the mineral. The Raman spectrum is characterised by an intense sharp band at 847 cm-1 assigned to the ν1 (A1g) symmetric stretching vibration. Intense sharp bands at 951, 994 and 1000 cm-1 are assigned to the ν3 (Eu, A2u, B1g) SiO4 antisymmetric stretching vibrations. Multiple ν2 SiO4 vibrational modes indicate strong distortion of the SiO4 tetrahedra. Multiple CaO and CuO stretching bands are observed. Raman spectroscopy confirmed by infrared spectroscopy clearly shows that hydroxyl units are involved in the kinoite structure. Based upon the infrared spectra, it is proposed that water is also involved in the kinoite structure. Based upon vibrational spectroscopy, the formula of kinoite is defined as Ca2Cu2Si3O10(OH)4•xH2O.

Thermal stability of the ‘cave’ mineral ardealite Ca2(HPO4)(SO4)•4H2O

Thermogravimetry combined with evolved gas mass spectrometry has been used to characterise the mineral ardealite and to ascertain the thermal stability of this ‘cave’ mineral. The mineral ardealite Ca2(HPO4)(SO4)•4H2O is formed through the reaction of calcite with bat guano. The mineral shows disorder and the composition varies depending on the origin of the mineral. Thermal analysis shows that the mineral starts to decompose over the temperature range 100 to 150°C with some loss of water. The critical temperature for water loss is around 215°C and above this temperature the mineral structure is altered. It is concluded that the mineral starts to decompose at 125°C, with all waters of hydration being lost after 226°C. Some loss of sulphate occurs over a broad temperature range centred upon 565°C. The final decomposition temperature is 823°C with loss of the sulphate and phosphate anions.

Thermal stability of newberyite Mg(PO3OH)•3H2O – a cave mineral from Skipton lava tubes, Victoria, Australia.

The mineral newberyite Mg(PO3OH)•3H2O is a mineral that has been found in caves such as the Skipton Lava Tubes (SW of Ballarat, Victoria, Australia), Moorba cave, Jurien Bay, Western Australia, and in the Petrogale Cave (Madura , Eucla, Western Australia). Because these minerals contain water, the minerals lend themselves to thermal analysis. The mineral newberyite is found to decompose at 145°C with a water loss of 31.96%, a result which is very close to the theoretical value. The result shows that the mineral is not stable in caves where the temperature exceeds this value. The implication of this result rests with the removal of kidney stones, which have the same composition as newberyite. Point heating focussing on the kidney stone results in the destruction of the kidney stone.

Thermal stability of stercorite H(NH4)Na(PO4)·4H2O – a cave mineral from Petrogale Cave, Madura, Eucla, Western Australia

Thermogravimetric analysis has been used to determine the thermal stability of the mineral stercorite H(NH4)Na(PO4)·4H2O. The mineral stercorite originated from the Petrogale Cave, Madura, Eucla, Western Australia. This cave is one of many caves in the Nullarbor Plain in the South of Western Australia. The mineral is formed by the reaction of bat guano chemicals on calcite substrates. Upon thermal treatment the mineral shows a strong decomposition at 191°C with loss of water and ammonia. Other mass loss steps are observed at 158, 317 and 477°C. Ion current curves indicate a gain of CO2 at higher temperature and are attributed to the thermal decomposition of calcite impurity.

Thermal stability of crandallite CaAl3(PO4)2(OH)5•(H2O) – a ‘cave’ mineral from the Jenolan Caves

Thermogravimetry combined with evolved gas mass spectrometry has been used to characterise the mineral crandallite CaAl3(PO4)2(OH)5•(H2O) and to ascertain the thermal stability of this ‘cave’ mineral. X-ray diffraction proves the presence of the mineral and identifies the products after thermal decomposition. The mineral crandallite is formed through the reaction of calcite with bat guano. Thermal analysis shows that the mineral starts to decompose through dehydration at low temperatures at around 139°C while dehydroxylation occurs over the temperature range 200 to 700°C with loss of OH units. The critical temperature for OH loss is around 416°C and above this temperature the mineral structure is altered. Some minor loss of carbonate impurity occurs at 788°C. This study shows the mineral is unstable above 139°C. This temperature is well above the temperature in caves, which have a maximum temperature of 15°C. A chemical reaction for the synthesis of crandallite is offered and the mechanism for the thermal decomposition is given.

Vibrational spectroscopy of synthetic archerite (K,NH4)H2PO4 : and in comparison with the natural cave mineral

In order to mimic the formation of archerite in cave minerals, the mineral analogue has been synthesised. The cave mineral is formed by the reaction of the chemicals in bat guano with calcite substrates. X-ray diffraction proves that the synthesised archerite analogue was pure. The vibrational spectra of the synthesised mineral are compared with that of the natural cave mineral. Raman and infrared bands are assigned to H2PO4-, OH and NH stretching and bending vibrations. The Raman band at 917 cm-1 is assigned to the HOP stretching vibration of the H2PO4- units. Bands in the 1200 to 1800 cm-1 region are associated with NH4+ bending modes. Vibrational spectroscopy enables the molecular structure of archerite to be analysed.

Molecular structure of the phosphate mineral brazilianite NaAl3(PO4)2(OH)4 : a semi precious jewel

The phosphate mineral brazilianite NaAl3(PO4)2(OH)4 is a semi precious jewel. There are almost no minerals apart from brazilianite which are used in jewellery. Vibrational spectroscopy was used to characterize the mol. structure of brazilianite. Brazilianite is composed of chains of edge-sharing Al-O octahedra linked by P-O tetrahedra, with Na located in cavities of the framework. An intense sharp Raman band at 1019 cm-1 is attributed to the PO43- sym. stretching mode. Raman bands at 973 and 988 cm-1 are assigned to the stretching vibrations of the HOPO33- units. The IR spectra compliment the Raman spectra but show greater complexity. Multiple Raman bands are obsd. in the PO43- and HOPO33- bending region. This observation implies that both phosphate and hydrogen phosphate units are involved in the structure. Raman OH stretching vibrations are found at 3249, 3417 and 3472 cm-1. These peaks show that the OH units are not equiv. in the brazilianite structure. Vibrational spectroscopy is useful for increasing the knowledge of the mol. structure of brazilianite.