43,000+ global companies doing business in the region 102,000+ key contacts related to companies and projects news and interviews about your industry in English Distribution of company announcements to the professional platforms finance portals and syndication of important corporate news to a wide variety of news aggregators and financial news systems Verity Resources Ltd (ASX:VRL) owns 100% of the Monument Gold project located near Laverton in Western Australia This project currently has a JORC-compliant (2012) Inferred resource of 3.257 Mt @ 1.4 g/t for 154,000 ounces Au.  Verity Resources also holds a supply critical metals portfolio via a joint venture that includes rare earth elements including licences in the "Lithium Valley" and Pocos de Caldas in the state of Minas Gerais globally known as prolific lithium and rare earth elements districts respectively The Company also owns 70% of the Pimenta Project a potential large-scale REE project in eastern Minas Gerais Verity Resources also holds a base and precious metals project in the Limpopo Mobile Belt in Botswana a district known for hosting major nickel and copper producing operations The Company's Botswana portfolio contains three flagship projects where high-grade Cu-Ag (Airstrip and Dibete) and a Maiden JORC Inferred Resource (Maibele North) have been discovered Maibele North currently hosts a JORC (2012) inferred resource of 2.4Mt @ 0.72% Ni and 0.21% Cu + PGE's + Co + Au and is located within 50km of the Selebi-Phikwe mine recently acquired by TSX-listed Premium Nickel Resources Ltd (TSX-V:PNRL)     Verity Resources Ltd (ASX:VRL) Appoints Paradigm Capital Founder Paul Dickson to the Board Verity Resources Limited (ASX:VRL) Placement to Accelerate Resource Growth at Monument Gold Project Verity Resources Limited (ASX:VRL) Pit Optimisation Study at Monument Gold Project Commenced Verity Resources Ltd (ASX:VRL) Quarterly Activities Report Verity Resources Ltd (ASX:VRL) Drilling Confirms Extension of Mineralisation at Monument Metrics details Topaz [Al2SiO4(F,OH)2] is one of the main fluorine-bearing silicates occurring in environments where variably acidic (F)/aqueous (OH) fluids saturate the silicate system In this work we fully characterized blue topaz from Padre Paraíso (Minas Gerais Brazil) by means of in situ synchrotron X-Ray and neutron powder diffraction measurements (temperature range 298–1273 K) combined with EDS microanalyses Understanding the role of OH/F substitution in topaz is important in order to determine the hydrophilicity and the exchange reactions of fluorine by hydroxyl groups and ultimately to characterize the environmental redox conditions (H2O/F) required for mineral formation The fluorine content estimated from neutron diffraction data is ~ 1.03 a.f.u (10.34 wt%) in agreement with the chemical data (on average 10.0 wt%) The XOH [OH/(OH + F)] (0.484) is close to the maximum XOH value (0.5) and represents the OH- richest topaz composition so far analysed in the Minas Gerais district Topaz crystallinity and fluorine content sharply decrease at 1170 K we suggest that this temperature may represent the potential initial topaz’s crystallization temperature from supercritical fluids in a pegmatite system The log(fH2O/fHF)fluid (1.27 (0.06)) is coherent with the fluorine activity calculated for hydrothermal fluids (pegmatitic stage) in equilibrium with the forming mineral (log(fH2O/fHF)fluid = 1.2–6.5) and clearly different from pure magmatic (granitic) residual melts [log(fH2O/fHF)fluid < 1] The modelled H2O saturated fluids with the F content not exceeding 1 wt% may represent an anomalous water-dominant / fluorine-poor pegmatite lens of the Padre Paraíso Pegmatite Field temperature up to 1000 °C) in the Al2O3–SiO2–H2O system the study of the OH/F ratio plays a key role to understand the topaz’s formation ambient Both sites lie close to the mirror plane in the space group Pbnm but their short distance (1.7 Å) prevents their simultaneous occupancy using the Hartree–Fock and Kohn–Sham self-consistent field method were reported: higher energy orthorhombic form Pbnm and a lower energy monoclinic form P21/c the real concentration and distribution of F and OH in natural topaz crystals can help to understand how the hydrogen bond geometry influences the OH behaviour with temperature Understanding these mechanisms is important in order to determine the hydrophilicity and the exchange reactions of fluorine by hydroxyl groups and ultimately to characterize the environmental redox conditions (H2O/F) required for the formation of topaz no detailed thermal structural investigations on natural topaz have been conducted so far preventing a rigorous modelling of the OH/F substitution in these minerals uncertainty about the H2O/F partitioning with the environment remains The aim of this work is therefore to investigate in depth the OH/F substitution in topaz in order to highlight the relationships between major element composition structural features and geological environments natural topaz from Minas Gerais (Brazil) were initially characterized by conventional chemical analyses by energy dispersive X-ray spectroscopy (EDS) These data provided important preliminary information about the composition of this group of topaz the chemical characteristics of this mineral need a more accurate determination in order to propose a robust chemical-physical model for crystal structure and crystallization conditions Two selected crystals were subsequently investigated using a combination of unconventional X-Ray sources and neutron powder diffraction In situ synchrotron X-ray powder diffraction (XRPD) was selected to obtain powder patterns of higher accuracy and precision angular resolution and beam collimation being considerably higher than those of conventional laboratory diffractometers horizontal polarization and tuneable X-ray wavelength reduced the fall in intensity as a function of 2θ as well as the high background level due to the sample fluorescence Temperature-dependent variation of the unit cell parameters and transient structural modifications upon heating were highlighted in the 298–1273 K temperature range combining synchrotron X-ray and neutron diffraction data the Rietveld refinement of powder diffraction data collected on samples heated in situ at selected temperatures was performed in order to observe: (a) the real symmetry of the selected topaz and its proton environment; (b) the concentration and distribution of F and OH in the selected sample; (c) the correlation as a function of temperature between thermal expansion fluorine content and the unit cell parameters; (d) the T-(P) conditions for topaz formation in the natural environment Our topaz present a clear to intense light blue colouration with no fades or colour flaws in all the samples collected All crystals have good transparency with medium–high clarity some solid inclusions of quartz and micas are recognizable Some liquid or biphasic inclusions are also present probably due to their pegmatitic origin All the liquid inclusions are iso-orientated only samples without inclusions were selected For this study a CAMSCAN MX 2500 Scan Electron Microscope (SEM) with an EDAX system for Energy Dispersive Analyses were used The SEM was equipped with a high brightness LaB6 cathode a set of natural minerals was used as standards for their specific elements: augite (Si and Ca) Relative analytical errors (1σ) of major elements were below 1.00% for Si and for Al; and 3.00–6.00% for F Images were collected both in SEI (secondary electron imaging) and BEI (backscattered electron imaging) The parameters used for the analyses were EHT 20 kV FIL 1.80A with a working distance of 25 mm Imaging and measurements were performed at the Microscopy Laboratory of the University of Padua They were then mounted on a standard goniometric head Powder diffraction patterns were collected in 10°–65° 2θ range with a step size of 0.008° and an exposure time of 1 s Each sample was subjected to the same heat treatment; samples were heated from room temperature to 1273 K with a heating rate of 5 K/min using a hot gas blower directing a hot air flux onto the spinning quartz-capillary Diffraction data were collected every 50 K The temperature was continuously measured by a thermocouple and calibrated using the quartz thermal expansion and phase transition A type-K thermocouple was located in the centre of the furnace in order to calibrate the temperature The same configuration was maintained during all data collection Projection of the topaz structure along the a (a) and c axes (b), respectively. The tetrahedral [SiO4]4− groups, in blue, are linked to octahedral chains of Al[O4(F,OH)2], in grey, in a zig zag fashion parallel to the c-axis. The smaller red, grey and white atoms are O, F and H, respectively. The structure image has been obtained using VESTA Version 3 (https://jp-minerals.org/vesta/en/download.html) no peaks larger than ± 0.32 e−/Å3 were present in the final difference Fourier map Lattice parameters refined from synchrotron X-ray are: a = 4.652373(18) Å The structural refinement with the neutron diffraction data collected at room temperature was performed in the space group Pbnm starting with the atomic coordinates obtained from the X-ray structural refinement The F-amount of our sample refined on the basis of the neutron diffraction data is 1.032 a.f.u; this correspond to 10.94 wt% (Table 4) the final difference Fourier map revealed the occurrence of a peak at x = 0.020 z = 0.141 which was then refined with the H scattering length The O–H bond distance was initially fixed and the constrain was completely removed in the last cycles of refinement (O4-H 0.979 (4) difference < 2σ) whereas the proton occupancy factor was fixed as a function of the oxygen at the F/O4 site (for the F/O4 site Evolution of unit cell parameters normalized with respect to room temperature values (a/a0 V/V0) from in situ synchrotron (a) and neutron diffraction (b) data A strong change in the unit cell parameters evolution is detected from neutron data (b) up to 1075 K a and b cell-axes have a similar expansion rate while the c-axis undergoes an increase up to about 1273 K Standard deviation errors are within the symbol size b and c increase as the temperature increases up to 1010 K indicating that the thermal expansion is the physical mechanism dominating this stage of the experiment Unit-cell axes refined from synchrotron data do not show any other modifications until the maximum temperature is reached A strong change in the unit cell parameters evolution is detected from neutron data up to this temperature a and b cell-axes have a similar expansion rate while the c-axis undergoes a significant increase up to about 1273 K These variations are reflected in the evolution of the unit-cell volume The temperature evolution was properly described using a polynomial expression: Thermal expansion model for in situ heating of the PadPar topaz, obtained from synchrotron (a) and neutron diffraction (b) analyses in the temperature range of 298 to 1273 K. Orange, yellow, green and blue symbols refer to Temperature vs Volume data selected for the EoS fitting (see text for details). Standard deviation errors are within the symbol size. Polyhedral evolution of topaz in the critical zone (1071–1273 K) expressed as V/V0 as obtained from neutron data The octahedral expansion (square symbols) is continuously balanced by a tetrahedral contraction (circle symbol) up to 1170 K accompanied by a crystallinity loss and a phase change are envisaged At higher temperature the concomitant expansion and contraction of tetrahedra and octahedra For sake of clarity octahedra (light blue) and tetrahedra (dark blue) are also represented Fluorine behaviour in topaz-mullite transition zone (1170–1273 K; see also Fig. 5b) a.p.f.u.: green pattern); weight fractions (wt fract.) of topaz and mullite in blue and red patterns At 1181 K topaz decomposition starts together with the appearance of a mullite phase (up to 0.10 wt F remains strongly partitioned in topaz up to 1225 K but reduces the weight fraction of this phase in the system by 50% fluorine is largely released by the topaz structure at 1252 K and concurrently mullite becomes the dominant phase (~ 70%) This F content is stabilized in the remnant topaz (~ 30%) up to 1270 K and its occurrence is strongly dependent on several factors such as air flow was successful in determining the fluorine content in topaz and its behaviour with increasing temperature The F/OH ratio in this phase is crucial not only for the forming gem process but also to better understand the circulation of fluids (H2O/F) in the forming environment in the following sections we use the equilibrium equations and formalism applied to the fluid state those from the Padre Paraíso pegmatite are undoubtedly a fluorine poor type (PadPar: F ~ 10.0–10.94 wt% versus worldwide average F ~ 18 wt%) and this topaz type of the Minas Gerais pegmatites has never been investigated before it is intriguing to determine the fluid activity in the PadPar pegmatite body and the fluorine and OH topaz contents (as determined by the proposed analytical protocol) can be utilized as indicators of the F (and OH) contents of fluids in equilibrium with this gem It is high challenging to extrapolate the ambient of mineral formation from the crystal itself since it is often doubtful that collected samples truly represent the in situ conditions at which minerals formed due to the fairly constant major-element composition of this mineral species the OH/F concentration ratio and fully characterized crystal structure (site occupancy) may reflect the nature of the fluid composition from which topaz formed relating the equilibrium constants of F-OH exchange in topaz: The potential initial crystallization temperature of topaz in the PadPar pegmatite system is also marked We applied a multi analytical strategy to fully characterize the gem quality of coloured topaz from pegmatites of the early Proterozoic Eastern Brazilian Pegmatite Province The relative simplicity of the topaz chemistry is complicated by the light nature of the major elements forming this mineral (Si therefore gaining chemical-physical information about the crystallization condition was challenging The successful strategy to combine EDS microanalyses with synchrotron X-Ray and neutron powder diffraction measurements allowed us to accurately determine the mineral structure the fluorine content is estimated to be ~ 1.03 a.f.u perfectly in agreement with the chemical data (on average 10.0 wt%) The chemical formula is Al1.92Si0.96O4.00F1.032OH0.968 with XOH = 0.484 Unit cell parameters indicate a positive thermal expansion up to 1010 K followed by a phase of octahedral expansion regularly counterbalanced by a tetrahedral contraction both fluorine content and topaz crystallinity decrease This maximum temperature is interpreted as the potential initial crystallization temperature of topaz in the pegmatite fluid system of possible fluids (or H2O-F saturated) coexisting with the PadPar topaz was modelled on the basis of the partitioning of F–(Cl)–OH behaviour between fluorine bearing minerals and late- post magmatic pegmatitic fluids we are confident to conclude that the PadPar fluorine-poor topaz was formed in a lens of fluorine poor/water saturated pegmatite fluids/ in the large early Proterozoic Eastern Brazilian Pegmatite province Fluid–rock interactions during UHP metamorphism: a review of the Dabie-Sulu orogen X-ray single-crystal structure refinement of an OH-rich topaz from Sulu UHP terrane (Eastern China)—structural foundation of the correlation between cell parameters and fluorine content The thermodynamic properties of topaz solid solutions and some petrologic applications Hydroxyl-rich topaz in high-pressure and ultrahigh-pressure kyanite quartzites High-pressure synthesis and properties of OH-rich topaz A neutron diffraction study of topaz: evidence for a lower symmetry The location of H in the high-pressure synthetic Al2SiO4(OH)2 topaz analogue A Rietveld refinement using neutron powder diffraction data of a fully deuterated topaz Pressure dependence of the hydrogen-bond geometry in topaz-OD from neutron powder diffraction and elasticity of hydrous aluminosilicate phase New insight into crystal chemistry of topaz: A multi-methodological study Effects of fluorine content on the elastic behaviour of topaz [Al2SiO4(F Effect of temperature and pressure on the crystal structure of topaz OH/F substitution in topaz studied by Raman spectroscopy Contrasting bonding behaviour of two hydroxyl-bearing metamorphic minerals under pressure: Clinozoisite and topaz Pressure dependence of the OH-stretching mode in F-rich natural topaz and topaz-OH Structure and strength of hydrogen bonds in inorganic solids Real-time powder diffraction studies of energy materials under non-equilibrium conditions Temperature dependence of the OH-stretching frequencies in topaz-OH Performing elemental microanalysis with high accuracy and high precision by scanning electron microscopy/silicon drift detector energy-dispersive X-ray spectrometry (SEM/SDD-EDS) The D20 instrument at the ILL: a versatile high-intensity 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of topaz Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides Partitioning of F-Cl-OH between minerals and hydrothermal fluids Chloride-hydroxyl exchange in biotite and estimation of relative HC1/HF activities in hydrothermal fluids apatite and silicate melt inclusions from the Tongchang mine SE China: Implications for the behaviour of halogens in mineralized porphyry systems Hydrothermal alteration and fluid chemistry of the endako porphyry molybdenum deposit Evolution of HF and HCl activity in magmatic volatiles of the gold-mineralized Emerald Lake pluton Constraints on hydrothermal fluid pathways within Mary Kathleen Group stratigraphy of the Cloncurry iron-oxide–copper–gold District Mineral chemistry of ore and hydrothermal alteration at the Sossego iron oxide–copper–gold deposit Mineral chemistry of hydrothermal biotite from the Kahang porphyry copper deposit (NE Isfahan) Geochemical characteristics of biotite from felsic intrusive rocks around the Sisson Brook W-Mo–Cu deposit west-central New Brunswick: An indicator of halogen and oxygen fugacity of magmatic systems Halogen-bearing minerals in syenites and high-grade marbles of Dronning Maud Land Antarctica: monitors of fluid compositional changes during late-magmatic fluid–rock interaction processes Origin of the high-temperature Olserum-Djupedal REE-phosphate mineralisation SE Sweden: A unique contact metamorphic-hydrothermal system The fingerprint of imperial topaz from Ouro Preto region (Minas Gerais state Brazil) based on cathodoluminescence properties and composition Colour in topaz from rhyolite domes of the San Luis Potosi volcanic field Topaz as an important host for Ge in granites and greisens Crystallisation of magmatic topaz and implications for Nb–Ta–W mineralisation in F-rich silicic melts: The Ary-Bulak ongonite massif Relation between cathodoluminescence and trace-element distribution of magmatic topaz from the Ary-Bulak massif The thermodynamic properties of fluor-topaz Thermodynamic analysis of the system Na2O-K2O-CaO-Al2O3-SiO2-H2OF2O)1: Stability of fluorine-bearing minerals in felsic igneous suites Hambergite-rich melt inclusions in morganite crystals from the Muiane pegmatite Mozambique and some remarks on the paragenesis of hambergite Topaz solid solution in the F-rich granitic rocks from Blond (NW Massif Central Temperatures and duration of crystallization within gem-bearing cavities of granitic pegmatites The enhanced element enrichment in the supercritical states of granite–pegmatite systems Calculation of HF and HCl fugacities from biotite compositions: Revised equations Primary melt inclusions in andalusite from anatectic graphitic metapelites: Implications for the position of the Al2SiO5 triple point Geochemistry of the granites and pegmatites of the Aracuai pegmatite district Geochemistry of muscovite from pegmatites of the Eastern Brazilian pegmatite province: a clue to petrogenesis and mineralization potential VESTA 3 for three-dimensional visualization of crystal “WinPLOTR: a Windows tool for powder diffraction patterns analysis Materials Science Forum” Proceedings of the Seventh European Powder Diffraction Conference (EPDIC 7) Download references The present study was granted by the “PRIN2017-2017L83S77” project of the Italian Ministry for Education acknowledge financial support from “Fondi di Ateneo University of Ferrara Thanks to Barbara Galassi and Steve Deforie (Brighton UK) for the revisions of the English language performed the in situ powder X-ray diffraction measurements performed the in situ powder neutron diffraction measurements performed the crystal sampling and selection and to the writing-reviewing and editing of the manuscript The authors declare no competing interests Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations Download citation DOI: https://doi.org/10.1038/s41598-021-82045-2 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