Dispersion of antimony from oxidizing ore deposits

The solubilities of brandholzite, [Mg(H2O)6][Sb(OH)6]2, and bottinoite, [Ni(H2O)6][Sb(OH)6]2, at 25 °C in water have been measured. Solubilities are 1.95(4) × 10-3 and 3.42(11) × 10-4 mol dm-3, respectively. The incongruent dissolution of romeite, Ca2Sb2O7, and bindheimite, Pb2Sb2O7, at 25 °C in 0.100 mol dm-3 aqueous HNO3 was also investigated. Equilibrium dissolved Sb concentrations were 3.3 ± 1.0 × 10-7 and 7.7 ± 2.1 × 10-8 mol dm-3, respectively. These values have been used to re-evaluate the geochemical mobility of Sb in the supergene environment. It is concluded that the element is geochemically immobile in solution and in soils. This was in part validated by an orientation soil geochemical survey over the Bayley Park prospect near Armidale, New South Wales, Australia. Anomalous soil Sb levels are confined to within 100 m of known stibnite mineralizatio

Structural and compositional variations of basic Cu(II) chlorides in the herbertsmithite and gillardite structure field.

© 2017 The Mineralogical Society. This document is the author’s final accepted version of the journal article. You are advised to consult the published version if you wish to cite from it

Raman Spectroscopy of Basic Copper (II) and Some Complex Copper (II) Sulfate Minerals: Implications for Hydrogen Bonding

Raman spectroscopy has been applied to the study of basic Cu sulfates including antlerite, brochiantite, posnjakite, langite, and wroewolfeite and selected complex Cu sulfate minerals. Published X-ray diffraction data were used to estimate possible hydrogen bond distances for the basic Cu sulfate minerals. A Libowitzky empirical expression was used to predict hydroxyl-stretching frequencies and agreement with the observed values was excellent. This type of study was then extended to complex basic Cu sulfates: cyanotrichite, devilline, glaucocerinite, serpierite, and ktenasite. The position of the hydroxyl-stretching vibration was used to estimate the hydrogen bond distances between the OH and the SO4 units. The variation in bandwidth of the OH-stretching bands provided an estimate of the variation in these hydrogen bond distances. By plotting the hydrogen bond O...O distance as a function of the position of the SO4 symmetric stretching vibration, the position of the SO4 symmetric stretching band was found to be dependent upon the hydrogen bond distance for both the basic Cu sulfates and the complex Cu sulfates

Studies of Natural and Synthetic Agardites

Agardite of formula [(Al,Nd,REE)Cu6(AsO4)3(OH)6.3H2O] has been discovered at Cobar, New South Wales, Australia. A series of synthetic agardites were analysed by X-ray diffraction and a correlation exists between the effective ionic radius of the REE3+ in the M site and the unit cell size for each respective agardite mineral. No value for the effective ionic radius of 9-coordinate Bi3+ has been reported but a value of approximately 115.5 pm is estimated from this correlation. The results of the TGA analyses show that the synthetic agardites are all fully hydrated, i.e., n = 3. Near infrared spectroscopy and mid-infrared spectroscopy has been used to characterise a group of synthetic agardites of formula ACu6(AsO4)2(OH)6.3H2O where A is a rare earth element. The hydroxyl stretching region is characterised by four bands observed at around 3568, 3489, 3382 and 3290 cm-1. The first two bands are attributed to the stretching mode of hydroxyl units and the last two bands to water stretching vibrations. The position of these bands indicates strongly hydrogen bonded water. The water in agardites is zeolitic type water. Near-IR spectroscopy shows a series of bands at 7242, 7007, 6809, 6770 and 6579 cm-1 attributed to the first overtones of the hydroxyl fundamentals. The NIR spectrum of agardite (Sm) is different and may be affected by electronic bands. Combination bands are observed at around 4404, 4343, 4340, 4294 and 4263 cm-1. Bands attributed to water combination modes are found at around 5200, 5173, 5082 and 4837 cm-1. Agardites are a group of minerals known for their REE content and have been rarely studied. NIR spectroscopy is an excellent technique for the characterisation and ready identification of these minerals

Thermal Decomposition of Agardites (REE) - Relationship Between Dehydroxylation Temperature and Electronegativity

The thermal decomposition of a suite of synthetic agardites of formula ACu6(AsO4)2(OH)6.3H2O where A is given by a rare earth element has been studied using thermogravimetric analysis techniques. Dehydration of the agardites occurs at low temperatures and over an extended temperature range from ambient to around 60 degrees Celsius. This loss of water is attributed to the loss of zeolitic water. The mass loss of water indicates 3 moles of zeolitic water in the structure. Dehydroxylation occurs in steps over a wide range of temperatures from 235 to 456 degrees Celsius. The mass loss during dehydroxylation shows the number of moles of hydroxyl units is six. There is a linear relationship between the first dehydroxylation temperature and the electronegativity of the REE

Use of Infrared Spectroscopy for the Determination of Electronegativity of Rare Earth Elements

Infrared spectroscopy has been used to study a series of synthetic agardite minerals. Four OH stretching bands are observed at around 3568, 3482, 3362, and 3296 cm⁻¹. The first band is assigned to zeolitic, non-hydrogen-bonded water. The band at 3296 cm⁻¹ is assigned to strongly hydrogen-bonded water with an H bond distance of 2.72 Å. The water in agardites is better described as structured water and not as zeolitic water. Two bands at around 999 and 975 cm⁻¹ are assigned to OH deformation modes. Two sets of AsO symmetric stretching vibrations were found and assigned to the vibrational modes of AsO₄ and HAsO₄ units. Linear relationships between positions of infrared bands associated with bonding to the OH units and the electronegativity of the rare earth elements were derived, with correlation coefficients >0.92. These linear functions were then used to calculate the electronegativity of Eu, for which a value of 1.1808 on the Pauling scale was found

Buttgenbachite from Bisbee, Arizona, USA : a single-crystal x-ray study

The single-crystal X-ray structure of a buttgenbachite (supposedly connellite) crystal from the Cole shaft, Bisbee, Arizona, USA has been determined at room temperature. The basic framework of the structure is the same as has been previously reported, except for a different pattern of substitution of chloride at the origin and variation in nitrate and chloride occupancies in the channels in the structure that accommodate these ions. No sulfate could be detected in the structure, which extends the range of stoichiometries and structural variants of the connellite-buttgenbachite series. A formula derived from the structure analysis for this particular specimen is Cu₃₆Cl₈.₁(NO₃)(OH)₆₂.₉·5.5H₂O

New data for boothite, CuSO4.7H2O, from Burraga, New South Wales

The ephemeral sulphate boothite, ideally CuSO4.7H20, has been collected from a tailings dump at the Lloyd copper mine at Burraga, New South Wales. Analysis of divalent metals by atomic absorption spectroscopy gave a formula of (Cu0.860Mg0.072Zn0.055Mn0.0l0Co0.003)∑1.000S04·7H20. A trace of Fe was also present. Powder X-ray diffraction data for boothite are reported for the first time. Refined unit cell constants are a = 14.190(10), b = 6.537(2), c = 10.825(6) Ã, a = 106.02(5)° (monoclinic, spacegroup P21/c). The mineral dehydrates spontaneously to chalcanthite, ideally CuS04.5H20, over several days

A supergene exploration model for Cobar style deposits

Knowledge of the geochemical “signature” of particular mineralisation is a prerequisite for exploration in the supergene environment. Particular elements may be widely dispersed compared to others and it is necessary to have some understanding of the chemical controls that govern this dispersion. With this in mind, it has been adventitious that the oxidised zone of the New Cobar orebody near Cobar, New South Wales, has been recently exposed. Primary mineralisation at New Cobar is of the typical “Cobar” type (Rayner, 1969; Stegman, 2000; Stegman & Pocock, 1996) and consists of arsenopyrite, (FeAsS), pyrite, (FeS2) marcasite, (FeS2), chalcopyrite (CuFeS2), galena, (PbS), sphalerite, ZnS, pyrrhotite, (Fe1-xS), and magnetite (Fe3O4). Cassiterite, (SnO2), native bismuth, bismuthinite, (Bi2S3), and rarer tungsten, molybdenum and selenium minerals are accessories, in common with a number of other deposits in the region. Quartz is the most common gangue mineral and very little primary carbonate mineralisation is present