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The present work studies the rodingite that is recorded for the first time as being associated to Al-Barramiya Neoproterozoic ophiolite at Eastern Desert of Egypt, Arabian-Nubian Shield (ANS). Al-Barramiya ophiolite is one of the most important ophiolitic sequences exposed in the ANS. It is affected by different styles of alterations included carbonatization, listvenitization, chloritization and rodingitization. The Neoproterozoic ophiolitic rocks of Al-Barramiya district consists of serpentinized peridotite and metagabbros. Serpentinized peridotites are highly altered to assemblages of talc-carbonate rocks, listvenite and magnesite, while metagabbro is partly converted into rodingite. The field studies indicate that serpentinite and rodingite in Al-Barramiya area display high-strain cataclastic deformation. Rodingite consists of garnet, diopside, vesuvianite and chlorite with minor epidote, prehnite, actinolite and opaque minerals. The garnets and vesuvianite are mostly concentrated near the peripheries of the studied rodingite masses, while clinopyroxene, chlorite, epidote and prehnite gradually increase inwards due to progressive decreasing water/rock ratio as fluids originally buffered by serpentinite move towards equilibrium with gabbroic bulk chemistry. Some rodingite samples preserve a few relics of igneous textures of ophiolitic metagabbros. Garnets are distinguished into andradite, hydroandradite and grossular. Pyroxene is represented mainly by secondary clinopyroxene beside primary fresh relics of diopside; the latter has high Mg# (0.92–0.97) similar to ophiolitic clinopyroxene in the ANS. Rodingite is enriched in CaO, Fe2O3 and MgO but depleted in SiO2, Al2O3 and Na2O compared to associated metagabbro. The association of rodingite with serpentinites and metagabbros suggests that Al-Barramiya rodingite is genetically related to serpentinization of ultramafic rocks. The rodingitization occurred during ocean floor alteration contemporaneous with the serpentinization process. The superposition of cataclastic deformation on the altered rocks indicates that alteration preceded obduction and occurred on the seafloor of the suprasubduction zone where Al-Barramiya ophiolite was originally emplaced. During serpentinization the olivine in the peridotite broke down and released Mg2+ in the metasomatic fluids and clinopyroxene broke down producing Ca-rich fluids. These fluids react with the mafic protoliths and enrich them in MgO and CaO. Also, serpentinization fluids react with the plagioclase of the metagabbro, releasing Ca from the mafic source and concentrated it in the rodingitized samples. The positive Eu anomalies beside high Sr contents of the rodingite can be inherited from a plagioclase-rich protolith such as ophiolitic metagabbro. The enrichment of rodingite in Th and U indicates two distinct solutions affected the gabbroic protolith because the alteration of depleted peridotite to serpentinite cannot be an efficient source to enrich these elements. The present study indicates that the rodingitization process underwent lower greenschist facies conditions associating metamorphism that caused serpentinization and released Ca-rich metasomatic fluids. [ABSTRACT FROM AUTHOR]

ABSTRACT This research focuses on the field observations, petrography, mineral chemistry and geochemistry of the serpentinised peridotite of Al‐Barramiya ophiolitic sequence to place constraints on their magmatic history and their geodynamic evolution. Al‐Barramiya ophiolitic rocks are a dismembered ophiolite which was strongly deformed and metamorphosed under greenschist to lower amphibolite facies. They comprise a mantle section dominated by highly serpentinised peridotite with less metapyroxenite and chromitite, as well as a crustal portion represented by metagabbros. Along shear zones, the ophiolite sequence was affected by several types of alteration. Extensive carbonate alteration is common in the ultramafic section, resulted in talc carbonates, listvenites and magnesite, while rodingitisation is common in the metagabbro resulted in rodingite. Despite the extensive serpentinisation, some fresh relics of primary mantle minerals such as Cr‐spinel, olivine and pyroxenes are preserved sporadically in the serpentinised peridotite. Few Cr‐spinel crystals are sometimes surrounded by subhedral flakes of Cr‐chlorite (kämmererite) that was formed due to replacement of Cr‐spinel during later alteration or regional metamorphism. The serpentinite samples are depleted in the total REE (0.56–1.19 ppm) with slightly negative to slightly positive Eu anomalies (0.89–1.28). The fresh cores of Cr‐spinel have Cr# mostly > 60, and the relics of pyroxenes and olivine are Mg‐rich suggesting that the Al‐Barramiya serpentinites are residual to high degrees of melt extraction. The estimated degrees of partial melting range between 18.2% and 20.7%. All the mineralogical and geochemical characteristics of the ultramafic section of the Al‐Barramiya ophiolites are most consistent with its formation in a fore‐arc setting. [ABSTRACT FROM AUTHOR]

Magnesite is an economically important mineral commonly found in ultramafic complexes worldwide, primarily in Archean to Proterozoic ultramafic complexes. This study focuses on the chemical and spectral characterization of magnesite found in the Neoarchean ultramafic rocks in the Attappadi region in the Southern Granulite Terrane of southern India. The research utilizes x‐ray diffraction analysis, hyperspectral, laser Raman, Fourier Transform Infrared, and Isotope Ratio Mass Spectrometry. The studied ultramafic rocks are part of a well‐exposed ophiolitic suite known as the Agali ophiolitic complex. Magnesite primarily occurs as veins, veinlets, and lenses within weathered ultramafic rocks. The hyperspectral analysis of the magnesite samples shows absorption bands in the shortwave infrared region, particularly around 2.3 and 2.5 μm, which correspond to the stretching and bending of the CO bond in the (CO3)2− ion in MgCO3. The laser Raman spectra show intensity peaks at 1095, 738, and 330 cm−1, which may be attributed to the translational and librational vibrations. The Fourier transform infrared data reveal transmittance at 1434, 880, and 747 cm−1, corresponding to MgO bond stretching and asymmetrical CO stretching. The x‐ray powder diffraction spectra exhibit diffraction peaks at 32°, 35°, 42°, 46° and 53°, characteristic of pure magnesite. The spectroscopic parameters derived from various analyses indicate that the magnesite is high quality and free from gangue minerals. Stable isotope analysis of the magnesite samples yielded δ13C values ranging from −5‰ to −9‰ and δ18O values in the range of 21‰–25‰. The estimated water temperature from which the magnesite has been precipitated is ~59 ± 3.9°C. Based on the field relations, mode of occurrence and isotopic signatures, the mineralization is considered to have been formed by the low‐temperature alteration of ultramafic rocks facilitated by CO2‐rich fluids in the near‐surface environment. This study compares the characteristics of magnesite from the study area with a few Neoproterozoic serpentinite‐hosted magnesite veins in the ophiolitic sequence of the Egyptian Eastern Desert, which is part of the Arabian Nubian shield. The research aims to contribute to understanding magnesite formation in Archaean to Proterozoic mafic–ultramafic rocks on the Earth's crust. It also provides insights into the geological processes that govern the genesis of ultramafic‐hosted magnesite globally, particularly in East Gondwana fragments. This information can enhance mineral exploration and resource evaluation in these regions, helping to identify economic prospects and assess the feasibility of magnesite resource extraction and utilization in East Gondwana fragments. [ABSTRACT FROM AUTHOR]

The main goal of this paper is to determine the order of the paragenetic sequence and phase transitions of the Ni–Fe sulfide association hosted in listvenites. Listvenites are hydrothermally altered mafic and ultramafic rocks that are often associated with active tectonic settings, such as transform faults, suture zones, and regional extensional faults, usually in contact with volcanic or carbonate rocks. Listvenitization is displayed by a carbonation process when the original olivine, pyroxene, and serpentine group minerals are altered to Mg–Fe–Ca carbonates (magnesite, calcite, dolomite, and siderite), talc, quartz, and accessory Cr spinel, fuchsite, and Ni–Fe sulfides. The formed rocks are highly reactive; therefore, very often, younger hydrothermal processes are observed, overprinting the mineralogy and geochemistry of the original listvenitization products, including accessory Ni–Fe sulfide paragenesis. The studied samples of listvenites were collected from two locations in Kosovo (Vardar Zone): Janjevo and Melenica. The Ni–Fe sulfide textures and relationships with the surrounding listvenite-hosted minerals were obtained using reflected and transmitted light microscopy, while their chemical composition was determined using an electron microprobe. They form accessory mono-or polymetallic aggregates that usually do not exceed 100 μm in size disseminated in the studied listvenites. Generally, the paragenetic sequence of Ni–Fe sulfides is divided into three stages. The first pre-listvenite magmatic phase is represented by pentlandite and millerite. The second listvenite stage consists of Ni–Co bearing pyrite I (Ni content up to 11.57 wt.% [0.24 apfu], and Co content up to 6.54 wt.% [0.14 apfu]) and differentiated thiospinels (violarite + siegenite ± polydymite). The last, late listvenite stage is represented by younger gersdorffite−ullmannite and base metal mineralization: pyrite + marcasite + sphalerite + galena ± chalcopyrite ± sulfosalts. The findings obtained should help in the interpretation of many disseminated accessory Ni–Fe–Co mineralizations associated with mafic and ultramafic rocks worldwide. [ABSTRACT FROM AUTHOR]

In the current study, effects of a carbon‐bonded magnesia (MgOC) refractory and a magnesia (MgO) refractory on the cleanliness of a high‐carbon Al‐killed steel and on the degree of refractory are investigated using laboratory experiments, thermodynamic calculation, and a kinetic modeling. The refractory/steel interface layer and inclusions in the steel are analyzed. After a 90 min contact between the refractory rod and the steel, the penetration of the molten steel into MgO refractory is small. An about 0.1 mm thick interface layer containing CaO–Al2O3–SiO2–MgO is generated at the boundary of magnesite particles while the composition of inclusions in the steel changes very little. The molten steel penetrated 1 mm into MgOC refractory through grain boundaries, forming channels due to the graphite consumption. A new 20 μm thick interface layer containing CaS and MgO is formed between the steel and MgOC refractory. The formation of CaS is favored at the steel/MgOC refractory and is rarely existed at the steel/MgO refractory during cooling process. The average content of MgO in inclusions increases from 6.22 to 30.05 wt% while the Al2O3 content in inclusions decreases from 84.57 to 69.95 wt% reacting for 90 min. [ABSTRACT FROM AUTHOR]

The hydrogenation of magnesite to CH 4 and MgO offers a powerful approach for CO 2 direct utilization. To deepen the understanding of the reaction mechanisms, (Mg 5 (CO 3) 4 (OH) 2 (H 2 O) 4 was selected as a model compound to gain insights into carbonate hydrogenation. A novel Ni/Fe/ZrO 2 catalyst with ferromagnetic properties was employed to facilitate the magnetic separation of the catalyst from the solid products. Thermodynamic simulation and experiments were conducted to address key issues such as gas evolution during catalytic hydrogenation, the effects of catalyst on CH 4 selectivity, and the separation of solid products and catalyst. The results indicate that lower temperatures favor CH 4 formation, whereas higher temperatures favor CO formation. Increasing Ni loading can enhance the CH 4 selectivity. With the presence of 10Ni/Fe/ZrO 2 catalyst, 100% CH 4 selectivity can be achieved at 300 °C. Moreover, 10Ni/Fe/ZrO 2 catalyst exhibits high magnetic responsiveness, facilitating the solid separation and the recycle of the catalyst. • A novel route for the hydrogenation of magnesite to produce CH 4 and MgO is proposed. • A ferromagnetic Ni/Fe/ZrO 2 catalyst enables efficient separation of the catalyst and product. • Low temperature favors CH 4 formation, while high temperature favors CO formation. • 100% CH 4 selectivity can be achieved at 300 °C with the presence of 10Ni/Fe/ZrO 2. [ABSTRACT FROM AUTHOR]

Gold, along with other highly siderophile elements, is hosted by Fe-Ni sulfide phases within peridotites and mantle melts. In this context, the lithospheric mantle emerges as a principal reservoir, providing materials crucial for the inception, augmentation, conveyance, and genesis of auriferous CO2-rich mantle fluids. EPMA and laser ablation ICP-MS data, integrated with petrographic and SEM studies, were used to assess the transfer of base and precious metals into the Earth's crust, discerning between inputs from subduction-related processes and post-formation metasomatism. The study focuses on sulfide minerals in serpentinized peridotites of the Abu Dahr ophiolite in the Eastern Desert of Egypt. Originating in a supra-subduction setting during the Neoproterozoic era, the Abu Dahr peridotites underwent serpentinization and contain discrete sulfide minerals, including pentlandite, nickeloan pyrrhotite, millerite, chalcopyrite, and violarite. The uneven distribution of calcite ± magnesite ± serpentine veins throughout the host ophiolitic rocks reflects the intricate interplay of serpentinization and carbonation, as fO2 and fCO2 conditions fluctuated. Geochemical data of the host rocks reveal a progressive geochemical evolution marked by concurrent silicification and carbonate alteration, driven by the interaction of ultramafic rocks with hydrothermal fluids, ultimately leading to the extensive silicification and formation of birbirite. The ICP-MS data show that pentlandite contains up to 6.11 ppm of Au, pyrrhotite up to 0.41 ppm, millerite 0.34 ppm, and violarite 0.12 ppm. The gold concentration in pentlandite is significantly higher than in pyrrhotite, millerite, and violarite, which exhibit lower but detectable levels of Au. Desulfurization reactions of sulfide minerals during progressive serpentinization triggered the release and redistribution of Au as well as base metals and highly siderophile elements. Published thermodynamic modeling at temperatures below 300 °C and pressures of 50 MPa closely replicates the mineral assemblage observed in the Abu Dahr ophiolites, including sulfide assemblages and variations in major elements such as Mg and Fe. This suggests that the serpentinization process, along with associated hydrothermal fluids, played a crucial role in the mobilization and redistribution of gold, particularly affecting its incorporation into secondary sulfides. The mobilization of Au and other highly siderophile elements during serpentinization occurred in an environment marked by strong oxidation, as indicated by the presence of acicular antigorite, magnetite, millerite, and goethite intergrowths. [ABSTRACT FROM AUTHOR]

The new mineral calcioveatchite, ideally SrCaB11O16(OH)5·H2O, is a Ca-Sr-ordered analogue of veatchite. It was found at the Nepskoe potassium salt deposit, Irkutsk Oblast, Siberia, Russia in halite-sylvite and sylvite-carnallite rocks, with boracite, hilgardite, kurgantaite, hydroboracite, volkovskite, veatchite, anhydrite, magnesite, and quartz. Calcioveatchite forms prismatic or tabular crystals up to 1 × 1.5 × 3 mm3 and crystal clusters up to 3 mm across. It is transparent and colourless with vitreous lustre. Calcioveatchite is brittle, cleavage is perfect on {010}, the Mohs' hardness is ca 2, Dmeas is 2.58(1), and Dcalc is 2.567 g cm−3. Calcioveatchite is optically biaxial (+), α = 1.543(2), β = 1.550(5), γ = 1.626(2), 2Vmeas = 30(10)°, and 2Vcalc = 35°. The average chemical composition (wt.%, electron microprobe, H2O calculated by stoichiometry) is: CaO 7.05, SrO 20.70, B2O3 61.96, H2O 10.22, and total 99.93. The empirical formula, calculated based on 22 O apfu = O16(OH)5(H2O) pfu, is Sr1.23Ca0.78B10.99O16(OH)5·H2O. Calcioveatchite is monoclinic, space group P21, a = 6.7030(3), b = 20.6438(9), c = 6.6056(3) Å, β = 119.153(7)°, V = 798.26(8) Å3, and Z = 2. Polytype: 1M. The strongest reflections of the powder XRD pattern [d,Å(I,%)(hkl)] are: 10.35(100)(020), 5.633(12)(110), 5.092(10)(120), 3.447(14)(060), 3.362(13)(101, 051), 3.309(38)(–102), 2.862(10)(012), and 2.585(19)(080). The crystal structure was solved based on single-crystal XRD data, R1 = 0.0420. Calcioveatchite (calcioveatchite-1M) is an isostructural analogue of veatchite-1M with the 11-fold cation polyhedron occupied mainly by Sr [Sr0.902(8)Ca0.098(8)] whereas the 10-fold polyhedron is Ca dominant [Ca0.686(7)Sr0.314(7)]. The chemical composition of veatchite from five localities in Russia (Nepskoe), Kazakhstan (Shoktybay and Chelkar in the North Caspian Region), and the USA (Tick Canyon and Billie Mine in California) was studied, and it is shown to exist in nature as a continuous, almost complete isomorphous series which extends from Ca-free veatchite, Sr2B11O16(OH)5·H2O, to calcioveatchite with the composition Sr1.14Ca0.87B10.99O16(OH)5·H2O. [ABSTRACT FROM AUTHOR]

Magnesite (MgCO3) is a valuable mineral with wide industrial applications; thus, geochemical familiarity and deposit quality are critical for making the best use of these resources. Tanzania is reported to have magnesite deposits in at least 12 different locations; however, four of these were chosen at random for study. This study aimed to examine the mineralogical and elemental composition of rock samples from Chambogo (KL), Muriatata (AR), Lobolosoiti (MN), and Chikaza (DM) using x-ray fluorescence (XRF) and powder x-ray diffraction (XRD). XRF examination revealed that sample KL, AR, MN, and DM, respectively, contain 45.21%, 46.06%, 43.21%, and 43.21% of magnesium oxide. Besides MgO, all samples contained SiO2, Fe2O3, Al2O3, CaO and several trace elements as impurities, with only calcium oxide, iron, arsenic, and chromium identified as impurities of concern. However, XRD analysis indicated magnesite as the major mineral phase in rock samples KL, AR, MN, and DM, with percentage concentrations of 65.2, 68.14, 63.87, and 68, respectively. In all rock samples, strong peaks at 2θ ∼ 33o, 43o, 54o and 55o, confirmed the crystalline nature of magnesite. Calcination of these samples however, resulted in peak shift and phase change, with main diffraction peaks generated at 2θ ∼ 36.9o, 42.9o and 62.3o, confirming the formation of crystalline MgO. Despite considerable contamination levels of CaO, iron, chromium, and arsenic in the samples, all samples had enough magnesite to be mined for industrial use. [ABSTRACT FROM AUTHOR]

The dismembered ophiolites in the Wadi Al-Barramiya area, Central Eastern Desert of Egypt, are one of a series of Neoproterozoic ophiolites present in the Arabian-Nubian Shield. Here we present new fieldwork, whole-rock geochemical data, and mineral chemistry of metapyroxenite and metagabbro associated with the Al-Barramiya ophiolite in order to constrain its nature and tectonic setting; in particular whether the ophiolite was formed in a subduction or non-subduction setting. The rocks selected were obtained from the mantle section (serpentinized peridotite), an ultramafic (pyroxenite) and the crustal section (metagabbro). The serpentinized peridotite is altered to talc carbonate and listvenite, and associated with magnesite. Pyroxenite occurs as irregular coarse-grained lenses of websterite and olivine websterite within the serpentinite and occurs adjacent to the ophiolitic metagabbro. The metagabbros form scattered allochthonous masses of various sizes that are distributed across the area. The ophiolitic rocks are metamorphosed from greenschist to lower amphibolite facies. Locally, fresh relicts of olivine and Cr-spinel can be found in the serpentinite, whereas pyroxenite has fresh relicts of olivine, clinopyroxene and Cr-spinel. Cr-spinel in the metapyroxenite is zoned, with Al2O3, Cr2O3 and MgO decreasing and FeOt increasing from cores to rims, reflecting the effects of metamorphism that selectively removed the now-depleted components. The metagabbros are characterized by enrichment in large-ion lithophile elements (LILE) over high field strength elements (HFSE) and are tholeiitic with a calc-alkaline affinity. The high Cr# (0.63–0.75) of fresh Cr-spinel relicts in the metapyroxenite, together with their low TiO2 contents (0.04–0.24 wt%), indicate that this rock is similar to highly refractory ultramafic rocks that evolved in a fore-arc setting. This is supported by the high forsterite content (Fo = 0.91–0.93) of fresh olivine and high Mg# (0.93–0.95) of fresh clinopyroxene. Clinopyroxenes in the metapyroxenite and metagabbro have the chemical characteristics of boninite, confirming the fore-arc setting. [ABSTRACT FROM AUTHOR]

The thermal decomposition and sintering kinetics of microfine magnesite were investigated to inaugurate a new One-step process for preparing high-density sintered magnesia. The optimal parameters for the discharging particle size of magnesite through ball milling were determined using an orthogonal experiment and Three-Way Measures ANOVA. The model for the thermal decomposition process of microfine magnesite was established through TGA-DSC and nonlinear regression analysis. Meanwhile, by describing the sintering process of microfine magnesite in detail through microstructure and CTE, the kinetic mechanisms of grain growth at different sintering stages were obtained. The results revealed that increasing the ratio of ball to powder can quickly obtain microfine magnesite which the bulk density reaches 3.45 g·cm−3 after One-step sintering. The thermal decomposition process required an activation energy of only 124.98 kJ·mol−1, which is much lower than existing technology and followed the Two-dimensional phase boundary reaction mechanism R 2. Additionally, the densification process was dominated alternatively by grain boundary diffusion and volume diffusion. This paper provided a detailed theoretical basis and leads a new direction in the One-step preparation of high-density sintered magnesia. [ABSTRACT FROM AUTHOR]

Magnesite is calcined to obtain active magnesium oxide, which is subsequently used in chemical reactions. There are high energy consumption and disorderly carbon dioxide emissions. Herein, direct utilization of all the elements in magnesite without roasting was achieved via surface modification activation technology. Sodium oleate was used as an activator; the reaction was carried out at 95°C for 4 h under alkaline conditions, and 60 mL sulfuric acid was added, resulting in the production of 9.5 g MgCO3·3H2O, 192.3 g magnesium sulfate heptahydrate, and 26.6 g wollastonite. The recovery rate reached 100%, while the conversion rate of magnesium oxide reached 83.6%. Density functional theory simulations revealed calcium and magnesium as the primary active sites. Sodium oleate adsorbs onto the magnesite surface through electrostatic adsorption and hydrogen bonding. Ionic and hydrogen bonds formed with Mg, Ca, and O in magnesite, which reduced the activation energy of magnesite. This paper presents a method for the chemical utilization of magnesite without roasting all the elements. [ABSTRACT FROM AUTHOR]

This is an article in the field of mining engineering. Magnesite in China is rich and good in quality. Its mineral quantity and grade rank the first in the world. It is widely used as the raw material for the production of magnesium oxide in industry. The change of microstructure of magnesite during calcination is the key to performance the properties of magnesia products. Taking this as the starting point, the technical progress of preparing high-performance magnesia products from magnesite is summarized firstly. Then, according to the restrictive factors of industry development, this article analyzes the future development trend of this field briefly.

• A novel olivine-magnesite composite material for removal of heavy metals was prepared by simply ball-milling. • Interface interaction of Mg 2 SiO 4 /MgCO 3 facilitated the formation of CdCO 3. • Significant fixation of Cd2+ was achieved even under weakly acidic conditions (pH=4). In this study, an efficient stabilizer material for cadmium (Cd2+) treatment was successfully prepared by simply co-milling olivine with magnesite. Several analytical methods including XRD, TEM, SEM and FTIR, combined with theoretical calculations (DFT), were used to investigate mechanochemical interfacial reaction between two minerals, and the reaction mechanism of Cd removal, with ion exchange between Cd2+ and Mg2+ as the main pathway. A fixation capacity of Cd2+ as high as 270.61 mg/g, much higher than that of the pristine minerals and even the individual/physical mixture of milled olivine and magnesite, has been obtained at optimized conditions, with a neutral pH value of the solution after treatment to allow its direct discharge. The as-proposed Mg-based stabilizer with various advantages such as cost benefits, green feature etc., will boosts the utilization efficiency of natural minerals over the elaborately prepared adsorbents. [Display omitted] [ABSTRACT FROM AUTHOR]

The article presents the results of studies of composite magnesium oxychloride iron-containing binders. The research is aimed at solving the problem of increasing operational durability and expanding the scope of application of magnesium materials. The purpose of the work is to study hydrate formation, hardening, and properties of composite magnesium binders with varying contents of iron compounds. Compositions of caustic magnesite (magnesium oxide) with iron oxides, with ferruginous minerals (andradite and pyrite), and with waste from the enrichment of magnetite ores have been studied. The scientific novelty of the research results lies in the identification of patterns of hydration of magnesium oxychloride binder with a high content (at least 50%) of iron compounds. The mutual influence of magnesium and ferruginous components during hydration and formation of the binder structure has been established. Schemes for the formation of hydrates involving andradite and pyrite have been proposed. The qualitative composition of the main hydrates of composite binders was determined by diffractometric and differential thermal analysis methods. The microstructure of the materials was studied by electron microscopy. The structure of magnesium paste made from a composite binder is formed by crystals of magnesium pentahydroxychloride and amorphous gel-like iron-containing hydrates. In composite binders containing iron oxide or andradite, magnesium hydroxychlorocarbonate is formed. The dependence of the stability of magnesium hydroxychlorocarbonate on the content of magnesium oxide and chloride was revealed. The patterns of the influence of iron compounds on the hydration and hardening of magnesium oxide form the basis for the development of a composite binder containing 50%–70% magnetite ore enrichment waste. A composite binder containing a ferrous man-made component is not inferior in strength properties to caustic magnesite and is characterized by high structural resistance to long-term operational impacts. [ABSTRACT FROM AUTHOR]

Given the depletion of high-quality magnesite deposits and the rising demand for high-end magnesium materials, the separation and utilization of high-calcium magnesite ores have become essential. However, the similar surface properties and solubility of semi-soluble salt-type minerals, pose significant challenges for the utilization of dolomite-rich magnesite resources. In this study, 1-hydroxypropane-1,1-diphosphonic acid (HPDP) was identified for the first time as a high-performance depressant for dolomite. Various tests, including contact angle measurements, ζ potential analysis, X-ray photoelectron spectroscopy, and atomic force microscopy, were conducted to elucidate the interfacial interaction mechanisms of HPDP on the surfaces of the two minerals at different scales. Additionally, molecular modeling calculations were used to detail the spatial matching relationship between HPDP and the crystal faces of the two minerals. It was emphasized that HPDP specifically adsorbed onto the dolomite surface by forming calcium phosphonate, ensuring that the dolomite surface remained hydrophilic and sank. Moreover, it was found that the adsorption strength of HPDP on the mineral surfaces depended on the activity of the metal sites and their spatial distribution. These findings provide a theoretical foundation for the molecular design of flotation reagents for high-calcium magnesite ores.

Al2TiO5 porous ceramics with high density and excellent thermal stability were prepared by the replica template method. MgO was introduced into Al2TiO5 by adding magnesite (MgCO3) to the slurry during the preparation process. The density and compressive strength of Al2TiO5 porous ceramics with varying MgCO3 content were studied. Additionally, the atomic-scale microstructure, thermal stability, and thermal shock resistance of the Al2TiO5 porous ceramics with 2 wt% MgCO3 were investigated. The results show that the Al2TiO5 porous ceramics doped with 2 wt% MgCO3 exhibit the highest density and compressive strength. The crystallographic orientation relationships of Al2TiO5 (ATO) - Mg0.3Al1.4Ti1.3O5 (MATO) and Mg0.3Al1.4Ti1.3O5 (MATO) - MgAl2O4 (MAO) are observed as (1 1 3) ATO//(1 1 2) MATO and [1‾ 2‾ 1] ATO//[1‾ 2‾ 1] MATO, (1 1 2) ATO//(2 2 0) MAO and [1‾ 2‾ 1] MATO//[1‾ 1 0] for the first time. In addition, the Al2TiO5 porous ceramics with 2 wt% MgCO3 remain phase stable after annealing at 1200 °C for 20 h, and the residual compressive strength is still higher than 88% after 20 cycles of the heating-cooling process at 1400 °C. These results indicate that the Al2TiO5 porous ceramics containing 2 wt% MgCO3 have potential applications in the porous media combustion (PMC) field.

Tetrahedrite-(Cu), Cu12Sb4S13, has been approved as a new mineral species (IMA2022–078) from the Bankov magnesite deposit near Košice, Slovak Republic where it occurs as anhedral grains, up to 0.4 mm across, associated with skinnerite, chalcostibite, famatinite, tetrahedrite-(Fe) and zoned aggregates of tennantite-(Cu) to tennantite-(Fe). Tetrahedrite-(Cu) is steel-grey, with a metallic lustre. Mohs hardness is ca. 3½–4 and calculated density is 5.029 g.cm–3. In reflected light, tetrahedrite-(Cu) is isotropic and grey with a bluish shade. Reflectance data for the four COM wavelengths in air are [λ (nm): R (%)]: 470: 31.1; 546: 30.1; 589: 29.9; and 650: 28.1. The empirical formula, based on electron-microprobe data (mean of 17 spot analyses), is Cu11.42Zn0.26Fe0.19(Sb4.06As0.08)Σ4.14S12.99. The ideal formula is Cu6(Cu4Cu2)Sb4S13, which requires (in wt.%) Cu 45.76, Sb 29.23 and S 25.01, total 100.00. Tetrahedrite-(Cu) is cubic, I $\bar{4}$ 3 m , with unit-cell parameters a = 10.3296(15) Å, V = 1102.2(5) Å3 and Z = 2. Its crystal structure was refined by single-crystal X-ray diffraction data to a final R 1 = 0.0347 on the basis of 261 unique reflections with F o > 4σ(F o) and 22 refined parameters. Tetrahedrite-(Cu) is isotypic with other tetrahedrite-group minerals. Previous findings of tetrahedrite-(Cu) are reported and some nomenclature issues, related to the Fe and Cu oxidation states, are discussed. At the Bankov deposit, tetrahedrite-(Cu) is related to hydrothermal, most probably Alpine, solutions strongly enriched in Cu, Sb and S. [ABSTRACT FROM AUTHOR]

Samples returned from the carbonaceous asteroid (162173) Ryugu by the Hayabusa2 mission revealed that Ryugu is composed of materials consistent with CI chondrites and some types of space weathering. We report detailed mineralogy of the fine‐grained Ryugu samples allocated to our "Sand" team and report additional space weathering features found on the grains. The dominant mineralogy is composed of a fine‐grained mixture of Mg‐rich saponite and serpentine, magnetite, pyrrhotite, pentlandite, dolomite, and Fe‐bearing magnesite. These grains have mineralogy comparable to that of CI chondrites, showing severe aqueous alteration but lacking ferrihydrite and sulfate. These results are similar to previous works on large Ryugu grains. In addition to the major minerals, we also find many minerals that are rare or have not been reported among CI chondrites. Accessory minerals identified are hydroxyapatite, Mg‐Na phosphate, olivine, low‐Ca pyroxene, Mg‐Al spinel, chromite, manganochromite, eskolaite, ilmenite, cubanite, polydymite, transjordanite, schreibersite, calcite, moissanite, and poorly crystalline phyllosilicate. We also show scanning transmission electron microscope and scanning electron microscope compositional maps and images of some space‐weathered grains and severely heated and melted grains. Although our mineralogical results are consistent with that of millimeter‐sized grains, the fine‐grained fraction is best suited to investigate impact‐induced space weathering. [ABSTRACT FROM AUTHOR]

This article studies the diverse effects of lithological on the properties of alkali-activated slag systems by blending different stone powders - limestone (LP), dolomite (DP), quartz (QP), and magnesite (MP). The physical and chemical properties of the raw materials were first analysed, followed by the investigation of reaction kinetics, resulting products, and microstructure. Rheology, strength, and shrinkage were then evaluated. Results indicate that increased LP and DP content improves flowability due to their particle size, while QP has limited effect. All stone powders reduce the degree of reaction, although the stronger affinity of LP and DP for Ca2+ promotes the formation of more reaction products. Microstructural analysis highlights superior bonding of LP and DP to the paste, as evidenced by the lower macro-scale strength loss at low mixing ratios. DP can also mitigate drying shrinkage, whereas MP has the most adverse effect due to its highest capillary pore proportion. [ABSTRACT FROM AUTHOR]

Cobalt-blue spinel from two localities (Qila and Trailside) on Baffin Island, Nunavut, Canada, are compared with other spinels from 12 occurrences in the same geological terrane and to Co-bearing blue spinel from other localities worldwide. Qila spinel is suitable for cutting cabochons, which commonly incorporate small amounts of associated calcite, dolomite, corundum, fluorapatite, pargasite and other silicates, as well as secondary cobaltpentlandite and fluid inclusions. Trailside spinel can be faceted into small gemstones (generally <0.2 ct), which rarely contain magnesite, fluorapatite, muscovite and CO2-rich fluid inclusions. The bright blue colour of the spinels from Qila and Trailside is due to TCo2+, although they also contain other chromophoric elements such as Fe and traces of Cr, Mn and V. Compared with other Mg-Al spinels from Baffin Island, those from Qila and Trailside are generally enriched in Co, Ni, Mn, Li and Be, and depleted in Ti, V and Cr. In addition, the Qila and Trailside Co-blue spinels are fairly chemically distinct from those of other world localities: they are depleted in V and Ti, fairly poor in Cr and Zn, and considerably enriched in Co and Mn. A new approach for the preliminary chemical discrimination of gem spinels is proposed by plotting the weighted chromophore concentrations in a ternary diagram (i.e. Cr+V vs 40×Co vs Fe/8). These weighted percentage values are also plotted against the ppmw concentrations of the chromophoric elements in X-Y plots, which provide further correlations of high Co with vivid Co-blue spinel and elevated Fe with overly dark non-gem spinel. This method can be applied to samples that are difficult or inefficient to characterise using spectroscopy, such as spinel grains in heavy-mineral concentrates obtained during regional exploration programmes. [ABSTRACT FROM AUTHOR]

Around 80% of the FeCr produced worldwide is utilized in stainless steelmaking. Thus, the growth of the stainless‐steel industry is directly related to FeCr production. Although the FeCr production in submerged arc furnace (SAF) is fairly stabilized, new challenges have emerged in the furnace operation due to the depletion of lumpy ores, high SiO2 content, and lower Cr/Fe ratio in the low‐grade ores. In this regard, the addition of various fluxes such as quartz, magnesite, and bauxite are considered to improve the Cr recovery in SAF operation, particularly in the context of low‐grade ores. In this study, thermodynamic calculations are performed to discuss the effect of various additives (MgO in magnesite, Al2O3 as bauxite, and SiO2 in quartz form) on Cr recovery and slag formation temperature. In addition, a comprehensive thermodynamic‐based process model has been developed for FeCr operation that captures the most important thermochemical reactions. The modeling results are compared with the plant data, and suitable modifications in the slag compositions are made to maximize Cr recovery. Moreover, new plant trials are performed with modified slag composition, and its effect on Cr recovery is also discussed. [ABSTRACT FROM AUTHOR]

Understanding the stability of magnesite in the presence of a hydrous fluid in the Earth's upper mantle is crucial for modeling the carbon budget and cycle in the deep Earth. This study elucidates the behavior of magnesite in the presence of hydrous fluids. We examined the brucite-magnesite [Mg(OH)2-MgCO3] system between 1 and 12 GPa by using synchrotron in situ energy-dispersive X-ray diffraction experiments combined with textural observations from quenched experiments employing the falling sphere method. By subjecting magnesite to varying pressure-temperature conditions with controlled fluid proportion, we determined the stability limits of magnesite in the presence of a fluid and periclase. The observed liquidus provides insights into the fate of magnesite-bearing rocks in subduction zones. Our findings show that magnesite remains stable under typical subduction zone gradients even when infiltrated by hydrous fluids released from dehydration reactions during subduction. We conclude that magnesite can be subducted down to and beyond sub-arc depths. Consequently, our results have important implications for the carbon budget of the Earth's mantle and its role in regulating atmospheric CO2 levels over geological timescales. [ABSTRACT FROM AUTHOR]

Fused magnesia is a main irreplaceable raw material of magnesia-carbon bricks for the linings of steelmaking converters, steelmaking electric furnaces and refining ladle slag lines,which has a production capacity of 4 miilion tons in southern Liaoning. However, due to its downstream market, production raw materials, as well as production technology and equipment,problems for the fused magnesia production exist such as the imbalance of supply and demand,high energy consumption and large fluctuation of product quality. Therefore, the status and changes of fused magnesia in southern Liaoning in recent years were expounded. The future development trend of fused magnesia was pointed out. [ABSTRACT FROM AUTHOR]

This study presents a detailed mineralogical description of carbonatization and silicification products derived from a serpentinite outcrop within the Vezirler ophiolitic mélange near Kula (Manisa, Western Türkiye). The investigated outcrop displays a significant alteration profile from bottom to top, including carbonatized and silicified serpentinite (CS-Srp), a coalesced carbonate nodule zone (Cnz), and an iron-oxide stained silica-carbonate alteration crust (Fscc). The blackish green to green coloured, very slightly carbonatized or non-carbonatized parts of the serpentinite is mainly made of serpentine polymorphs, bastite transformed orthopyroxene, chromite, iron-oxides, and andradite. Minor carbonatization is observed with dolomite and hematite-bearing coronas around andradite in contact with serpentine. In contrast, CS-Srp comprises hydromagnesite-hydrotalcite nodules within a greenish-gray serpentinite matrix. Near the Cnz contact, discrete magnesite nodules are present, while the Cnz consists of agglomerated magnesite nodules. Fscc above the Cnz, contains magnesite nodules and dolomite-silica stockwork in the lower segment and only dolomite-silica stockwork in the upper segment. The rhythmically zoned magnesites suggest changing reactant phases during carbonatization influenced by temperature, Si solubility, XCO2, reactive surface area, and water/rock ratio. Tectonic control is indicated by the contact between Fscc and Cnz, suggesting a roughly N60W strike and a low-angle NE dipping trend (< 10°). The minimal presence of Ca-bearing minerals in the alteration paragenesis suggests Ca-deficient protoliths and metasomatizing fluids. The co-existence of magnesite and hydromagnesite-hydrotalcite at the same outcrop is attibuted to shifting pH of the metasomatizing fluid, percolation through the serpentinite and conductive cooling. Various factors, including reactant phase abundance and fluid nature likely influenced the final alteration mineralogy, providing insight into surface/near-surface transformations expected in CO2 storage projects in peridotite terranes. [ABSTRACT FROM AUTHOR]

This study tests experimentally the hypothesis that calculated bulk compositions of multiphase solid inclusions present in minerals of ultrahigh pressure rocks, can be equated to the composition of the former trapped fluids. We investigated samples from the ultrahigh pressure garnet peridotites of the Bohemian Massif, spatially associated with ultrahigh pressure crustal rocks and representing a former subduction interface environment. Inclusions present in garnets, composed of amphibole + Ba-mica kinoshitalite + carbonates (dolomite + magnesite + norsethite), were taken to their entrapment conditions of c. 4.5 GPa and 1075 ºC. They (re)crystallized into a garnet fringe at the boundary between inclusion and host garnet, kinoshitalite ± olivine, carbonatite melt, and a hydrous fluid. Although the latter may have exsolved from the carbonatite melt upon quenching, microstructures suggest it was present at trapped conditions, and mass balance indicates that it corresponds to a Na-K-Cl-F-rich saline aqueous fluid (brine). Experiments demonstrate the stability of kinoshitalite at 4.5 GPa and 1075 ºC, and suggest that Ba-rich mica + carbonatite melt + brine coexisted at near-peak conditions. Barium is compatible in the carbonatite melt and mica with respect to the brine, with a partition coefficient between carbonatite melt and mica of ≈ 2.5–3. The garnet fringe formed from incongruent reaction of the former inclusion assemblage due to reversing the fluid(s)-host garnet reaction that occurred upon natural cooling/decompression. Loss of H2 or H2O from the inclusions due to volume diffusion through garnet and/or decrepitation, during geological timeframes upon decompression/cooling, may have prevented rehomogenization to a single homogeneous fluid. Our study shows that great care is needed in the interpretation of multiphase solid inclusions present in ultrahigh pressure rocks. [ABSTRACT FROM AUTHOR]

BACKGROUND: Struvite (MgNH4PO4.6H2O) precipitation is a sustainable approach that can offer simultaneous removal/recovery of nutrients from biogas plant effluents. However, most biogas plant effluents contain a higher molar concentration of nitrogen (N) than magnesium (Mg) and phosphorus (P). Therefore, the external addition of Mg2+ and phosphate (PO43‐) salts is needed to maximize the recovery. In this study, Mg‐rich waste magnesite powder and P‐rich bone meal were used as sustainable additives. The Box–Behnken design was applied to determine optimum conditions of process parameters (pH, Mg:N and P:N molar ratios) to maximize ammonium‐nitrogen (NH4‐N), PO4‐P and Mg2+recoveries. RESULTS: NH4‐N, PO4‐P and Mg2+ recoveries were in the ranges 78.5%–96.9%, 69.2%–96.3% and 75.1%–99.9%, respectively. The actual and predicted values showed significant consistency, indicating that the model is satisfactory. Under optimum conditions (pH = 9.0, Mg:N = 2.2, P:N = 1.8), 97.8 ± 0.1% NH4‐N, 96.6 ± 0.31% PO4‐P and 84.4 ± 0.9% Mg2+ recovery were attained. The X‐ray diffraction results confirmed the sole presence of struvite crystals. Scanning electron microscopy images showed irregular prismatic orthorhombic crystals and amorphous material depositions on precipitates of ~25 μm crystal size. The product was 49% struvite with 15.2% P content. The heavy metal content was lower than regulatory limits. CONCLUSION: Even though waste material and industrial by‐products have been used as additives in this process, high NH4‐N and PO4‐P recoveries were recorded under optimum conditions. These results are promising and illustrate a powerful example of industrial symbiosis, and the precipitate containing struvite can serve as a valuable product. © 2024 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

Traditional magnesite desilication flotation collectors struggle to efficiently remove quartz from low-grade magnesite, prompting the exploration of new, highly selective flotation collectors. Addressing this need has become a focal point in mineral processing research. This study introduced heptadecylamine ethylimidazoline quaternary ammonium salt (ODD) as a quartz flotation collector for separating quartz from magnesite. Flotation experiments involving single minerals and artificially mixed minerals demonstrated that magnesite and quartz could be effectively separated under specific conditions: an ODD concentration of 40mg/L and pH=7.0. Zeta potential assessments revealed that the adsorption of ODD increased the potential of quartz by 4.4 times compared to magnesite. Furthermore, contact angle measurements illustrated that ODD selectively increased the hydrophobicity of the quartz surface while not affecting the contact angle of magnesite. X-ray photoelectron spectroscopy (XPS) analysis indicated that ODD's selective adsorption at the quartz surface through interaction with the O sites on quartz rather than magnesite. Drawing from these findings, a flotation separation model from magnesite and quartz under the influence of ODD was formulated. [ABSTRACT FROM AUTHOR]

The synergistic effect of sodium dodecyl benzene sulfonate (SDBS) on the flotation separation of magnesite and dolomite using sodium oleate (NaOL) as a collector has been studied through flotation experiments, zeta potential measurements, contact angle measurements, Fourier transformation infrared spectroscopy analysis (FT-IR), particle size measurements and transmittance measurements. The flotation experiments show that when the synergist, SDBS, is added to the collector, NaOL, the collecting ability and ion resistance of NaOL can be improved so that the flotation separation of magnesite and dolomite can be realized. Zeta potential measurements, contact angle measurements and FT-IR analysis indicate that SDBS and NaOL can co-adsorb on the surface of magnesite. Particle size measurements and transmittance measurements show that SDBS can also improve the dispersion and solubility of NaOL in an aqueous solution, so as to achieve a synergistic effect. [ABSTRACT FROM AUTHOR]

It is essential to determine the most suitable machining method for magnesite-reinforced Aluminium 6061 composites, which possess excellent mechanical properties, especially notable tensile strength and hardness. The composites were produced using a stir-casting technique, incorporating reinforcements of lightly-calcined magnesite, dead burnt magnesite, and waste magnesite in weight fractions of 2.5%, 5%, and 7.5% within an aluminium 6061 matrix. Wire electrical discharge machining was employed to investigate the machining characteristics of these composites, using controllable process parameters such as cutting speed, pulse-on and pulse-off times, and the weight fraction of magnesites. Two performance indicators such as surface roughness and material removal rate were tested for various parameter combinations by central composite design. To comprehend the impact of the study parameters, contour charts were drawn. MRR increases at a high cutting speed of 2 mm/min when the pulse-on time changes from 120 μs to 125 μs. SR increases when the pulse-on times above 120 μs at all cutting speeds. High cutting speeds make high MRR irrespective of the weight fractions of reinforcement. High pulse-on times make the material melt more, which increases the material removal rate. Because specimen surface material erodes quickly and forms microcracks, high pulse-on time also results in high surface roughness. To optimize the WEDM machining conditions for each composite, hybrid SSO-DF and DFO-DF optimizers were developed by combining the desirability function with Salp-swarm optimization and Dragonfly optimization algorithms. The cutting speed of 2 mm/min and the pulse-on time of 114 μs produce the best performances on the composites. [ABSTRACT FROM AUTHOR]

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Abstract The mechanism of interaction between magnesite mineral and phosphoric acid (0.001–0.5 M) in addition to the determination of the protective properties for Ti alloy (working electrode) in phosphoric acid both with and without an inhibitor have been investigated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements. Results of electrochemical tests show that the corrosion resistance of titanium alloy in phosphoric acid solution only increased and hydrogen production decreased by either decreasing acid concentration or increasing immersion time associated with the thickening of the oxide film formed on the alloy surface. On adding magnesite, the corrosion resistance of Ti alloy is enhanced by increasing the phosphoric acid concentration (0.001–0.5 M) due to the formation of sparingly soluble magnesium phosphate film on the alloy surface that inhibits the effect of increasing hydrogen evolution reaction due to the pH value decreases. The increasing adsorption behavior of the magnesite inhibitor and decreasing its diffusion were deduced from EIS measurements. Thus, the addition of 3% magnesite minimizes the corrosion by forming a new protective film (Mg3(PO4)2), which differs from the traditional passive film and prevents the effect of the increase of hydrogen evolution. The surface morphology and chemical composition of the tested alloy were determined using scanning electron microscopy (SEM), Fourier transform Infra-Red spectroscopy (FTIR), X-ray diffraction (XRD), X-ray Fluorescence (XRF) and In situ Raman spectroscopy.

Herein, MgO–C refractories were prepared using fused magnesite, aluminum powder, and silicon powder as antioxidants and different kinds of graphite as carbon sources at 1200°C–1600°C. The microstructure and mechanical strength of MgO–C refractories were studied. The results showed that using cobalt‐loaded expanded graphite as partial carbon source, carbon nanotubes (CNTs) were formed in situ in MgO–C refractories at 1200°C, and the CNTs gradually reacted with Si to form SiC fibers over 1400°C. Consequently, the mechanical strength of MgO–C refractories was significantly improved. [ABSTRACT FROM AUTHOR]

Subduction of carbonate‐bearing oceanic plates into Earth's interior recycles carbon from the surface to the deep mantle. The subducted carbonates can significantly affect mantle properties and dynamics. Magnesite is recognized as one of the major potential carbon hosts in the deep mantle because of its stability up to deep lower mantle conditions. However, despite many previous studies on the equation of state and elastic properties of magnesite, large discrepancies still exist for its elastic moduli and their pressure and temperature derivatives. Here we report in situ density and elastic wave velocity measurements on a natural magnesite at simultaneous high pressure‐temperature conditions up to ∼8 GPa–1073 K in a multi‐anvil apparatus using ultrasonic and synchrotron X‐ray techniques. Global fitting of the data set to finite strain equations yields KS0 = 114.0 ± 1.2 GPa, KS′ ${K}_{S}^{\prime }$ = 4.9 ± 0.3, ∂KS∂TP ${\left(\frac{\partial {K}_{S}}{\partial T}\right)}_{P}$ = (−0.019 ± 0.002) GPa/K, G0 = 68.6 ± 0.4 GPa, G′ = 1.6 ± 0.1, and ∂G∂TP ${\left(\frac{\partial G}{\partial T}\right)}_{P}$ = (−0.018 ± 0.001) GPa/K. Compared to other major upper mantle and transition zone minerals, magnesite has intermediate VP, the lowest VS, and the lowest density. Thus, magnesite possesses higher VP/VS ratio than other mantle minerals in normal mantle regions, whereas this feature is less pronounced in subduction zone environments. Modeling of the velocity profiles of carbonated lithologies along different geotherms suggests that moderately‐enriched magnesite domains are unlikely to be detected seismically in the Earth's mantle. Plain Language Summary: Carbon can be transported into Earth's interior by subducting slabs in the form of carbonates. Magnesite (MgCO3) is recognized as one of the most important oxidized carbon hosts inside the Earth. Accurate knowledge of the thermoelastic properties of magnesite at Earth's mantle conditions is thus needed in order to evaluate its seismic detectability and effect on mantle seismic structure and dynamics. Despite many previous efforts in determining the properties of magnesite, large discrepancies still exist for its elastic moduli and their pressure and temperature derivatives. In this study, we determined both the density and elastic wave velocity of magnesite at high pressure and temperature conditions up to ∼8 GPa–1073 K using in situ ultrasonic measurements combined with synchrotron X‐ray techniques in a multi‐anvil press. Our high‐quality data tightly constrained the thermoelastic parameters of magnesite, which were then used to model the velocity and density of magnesite and magnesite‐bearing rocks in the Earth's mantle along different geotherms. Our results show that despite the fact that magnesite has the lowest VS compared to other major mantle minerals, moderately‐enriched magnesite domain is difficult to detect in the Earth's mantle based on its seismic velocity. Key Points: In situ density and elastic wave velocity measurements on magnesite at simultaneous high P‐TThe thermoelastic properties of magnesite are tightly constrained by high‐quality P‐ρ‐T‐VP‐VS data setModerately‐enriched magnesite domains are difficult to detect seismically in the Earth's mantle [ABSTRACT FROM AUTHOR]

The accumulation of magnesite tailings (MT) poses challenges such as resource wastage, land occupation, dust generation, and environmental pollution, thereby jeopardizing both physical and mental health. Urgent attention is required for the proper treatment of this solid waste material. An in‐depth investigation into enhancing the flotation processes of MT is essential. A comprehensive comprehension of the surface properties of MT and its principal gangue minerals assumes paramount importance in facilitating the desilication and decalcification of MT via flotation. In this investigation, a first‐principles study grounded in density functional theory was employed to scrutinize the surface properties, as well as the similarities and differences in flotability, of four minerals‐quartz, magnesite, dolomite, and calcite. The findings reveal that quartz's primary cleavage plane is (1 0 1), whereas that of magnesite, dolomite, and calcite is (1 0 4). The surfaces of magnesite, dolomite, and calcite exhibit chemical similarities, with Ca atoms demonstrating higher reactivity than Mg atoms. The hydrogen bonding between dodecylamine and quartz emerges as the most robust, while adsorption energies with the three carbonate minerals exhibit minimal disparity. The ongoing focus lies on the selection and optimization tests of decalcification reagents. A moderate quantity of dodecylamine manifests a certain desilication effect. However, excessive dosage compromises selectivity. The first‐principles approach offers guiding significance for elucidating the surface properties of MT and its primary vein minerals, along with investigating the adsorption mechanisms of flotation regents. [ABSTRACT FROM AUTHOR]

Copyright of Refractories / Naihuo Cailiao is the property of Naihuo Cailia (Refractories) Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The mechanism of interaction between magnesite mineral and phosphoric acid (0.001–0.5 M) in addition to the determination of the protective properties for Ti alloy (working electrode) in phosphoric acid both with and without an inhibitor have been investigated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements. Results of electrochemical tests show that the corrosion resistance of titanium alloy in phosphoric acid solution only increased and hydrogen production decreased by either decreasing acid concentration or increasing immersion time associated with the thickening of the oxide film formed on the alloy surface. On adding magnesite, the corrosion resistance of Ti alloy is enhanced by increasing the phosphoric acid concentration (0.001–0.5 M) due to the formation of sparingly soluble magnesium phosphate film on the alloy surface that inhibits the effect of increasing hydrogen evolution reaction due to the pH value decreases. The increasing adsorption behavior of the magnesite inhibitor and decreasing its diffusion were deduced from EIS measurements. Thus, the addition of 3% magnesite minimizes the corrosion by forming a new protective film (Mg3(PO4)2), which differs from the traditional passive film and prevents the effect of the increase of hydrogen evolution. The surface morphology and chemical composition of the tested alloy were determined using scanning electron microscopy (SEM), Fourier transform Infra-Red spectroscopy (FTIR), X-ray diffraction (XRD), X-ray Fluorescence (XRF) and In situ Raman spectroscopy. [ABSTRACT FROM AUTHOR]

In the context of carbon peak and carbon neutrality, the resource utilization of solid waste tailings has important scientific research value and environmental protection significance. In this work, porous MgO-based ceramics with excellent mechanical and thermal insulation properties were prepared by the direct firing method and using lanthana as an additive. The results shows that the 2CaO·4La 2 O 3 ·6SiO 2 phase in-situ formed by the lanthana additive simultaneously improves the apparent porosity, thermal insulation, and mechanical properties of the prepared MgO-based ceramics. In particular, the 2CaO·4La 2 O 3 ·6SiO 2 phase increases apparent porosity by inhibiting shrinkage, from 51.78% to 53.34% (with 7.5 wt% of lanthana), and the thermal conductivity correspondingly decreases from 0.493 to 0.324 W·m−1 K−1 (800 °C); meanwhile, the 2CaO·4La 2 O 3 ·6SiO 2 phase improves the cold cpmpressive strength (from 6.89 to 11.13 MPa) and refractoriness under load (from 1345 to 1405 °C) by modifying the low-melting phase and cross-connecting the rod-like structure, respectively. Consequently, a potential strategy for the utilization of magnesite tailings is proposed, and the prepared porous ceramics are expected to be applied in the field of high-temperature thermal insulation. [ABSTRACT FROM AUTHOR]

Carbonate-bearing sediments, containing calcite, dolomite or magnesite as major carbonate components, are important constituents of sedimentary sequences deposited on passive margins through Earth's history. When involved in collisional orogenic processes, these sediments are metamorphosed at variable temperatures and pressures, and undergo decarbonation reactions. While the orogenic metamorphism of some of these lithologies (i.e. impure limestones and dolostones, marls sensu stricto and calcareous pelites) is relatively well understood, very little is known about the metamorphic evolution and decarbonation history of mixed carbonate–silicate rocks in which either dolomite or magnesite is the dominant carbonate component. Here we present the results of a petrologic study of representative samples of metasediments from Central Nepal, derived from Proterozoic dolomitic and magnesitic protoliths metamorphosed during the Himalayan orogeny. The main metamorphic assemblages developed in sediments originally containing different amounts of dolomite or magnesite are characterised in detail. Forward thermodynamic modelling applied to seven samples allows constraints to be placed on (i) the main decarbonation reactions, (ii) the P–T conditions under which these reactions took place, (iii) the composition of the fluids, and (iv) the amounts of CO2 released. We conclude that the CO2 productivity of dolomitic and magnesitic pelites and marls originally containing 15–40% carbonate is significant (>5.5 ± 1.0 CO2 wt% and up to 10.5 ± 1.5 CO2 wt%), whereas for carbonate contents above 60–70%, CO2 productivity is negligible unless aqueous fluids infiltrate from the outside and trigger decarbonation reactions. Since the dolomitic and magnesitic protoliths are significantly abundant in the sedimentary sequences involved in the still active Himalayan orogen, the decarbonation processes described here could contribute to the diffuse CO2 degassing currently observed at the surface. Furthermore, we propose for the first time that the peculiar magnesium-rich assemblages investigated in this study may derive from evaporitic protoliths, and that the whole Upper Lesser Himalayan Sequence may therefore represent the metamorphic product of a Proterozoic sequence consisting of alternating layers of carbonatic, evaporitic and pelitic sediments. [ABSTRACT FROM AUTHOR]

Flotation separation of magnesite from dolomite in the presence of SSZS (sodium silicate modified with zinc sulfate) as an inhibitor and NaOL (sodium oleate) as a collector has been studied via flotation tests, zeta potential measurements, contact angle measurements, and Fourier transformation infrared spectroscopy analysis (FT-IR). The flotation tests show that NaOL has strong collecting capacity in magnesite and dolomite flotation, so it is difficult to separate two minerals via flotation without inhibitors. SSZS is used as the depressant, which can selectively inhibit dolomite flotation and has little depression effect on magnesite. Zeta potential measurements, contact angle measurements, and FT-IR analysis indicate that SSZS can adsorb strongly onto dolomite's surface and has a weak adsorption effect on magnesite. The adsorption of SSZS prevents NaOL from acting on the surface of dolomite. On the contrary, because there is little adsorption of SSZS onto magnesite, NaOL can still adsorb onto magnesite's surface. [ABSTRACT FROM AUTHOR]

Orogenic peridotites in the crystalline basement of the northwestern Bohemian Massif contain multiphase solid inclusions (MSI), which are interpreted to be crystallisation products of trapped former carbonate–silicate melts metasomatizing their host rocks. We applied conventional thermobarometry and forward thermodynamic modelling to constrain the P–T evolution ranging from the peak metamorphic conditions of the investigated harzburgite and lherzolite, through entrapment of the melts in the outer parts of garnets, to the (re)-equilibration of the MSI assemblages. The peak conditions of c. 1100 °C/4.5–5.5 GPa are recorded by garnet cores and large pyroxene porphyroclasts. The melt entrapment, during which garnet outer parts grew, was associated with influx of the metasomatizing liquids and probably took place during the early stage of the exhumation. Thermodynamic model of amphibole-free MSI assemblage comprising kinoshitalite/Ba-rich phlogopite (approximated by phlogopite in the model), dolomite, magnesite, clinopyroxene, orthopyroxene, garnet and chromite provided robust estimate of P and T of its (re)-equilibration, c. 900–1000 °C, 1.8–2.2 GPa. Furthermore, the lack of olivine reflects co-existence of COH fluid with high X(CO2) = CO2/(CO2 + H2O) ≥ 0.6. Models employing identical P–T–X(CO2) parameters successfully reproduced the other two amphibole-bearing assemblages observed. The modelled stability fields show perfect alignment with a characteristic isobaric segment of the solidus curve of carbonated peridotite. This co-incidence implies that the (re)-equilibration corresponds to the termination of the melt crystallisation once the near-isothermal exhumation path intersected the solidus. Decreased solubility of silicates at the carbonated peridotite "solidus ledge", inferred from the published experimental data, as well as concentric textures of some MSI indicates sequential crystallisation from the early silicates to late dolomite. The carbonated "solidus ledge" is a relatively narrow boundary in the lithospheric mantle capable of an abrupt immobilisation of fluxing or transported carbonated melts. The investigated rocks are estimated to store approximately 0.02 kg C/m3 (or 6 ppm C) occurring as carbonates in the MSI. [ABSTRACT FROM AUTHOR]

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Copyright of Industrial Minerals & Processing / Huagong Kuangwu yu Jiagong is the property of Industrial Minerals & Processing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this work, the synergistic effect of hydrochloric-acid etching and inhibitors on the flotation separation of magnesite and dolomite in the sodium oleate (NaOL) system was studied. Flotation tests revealed that the synergistic effect of acid etching and sodium hexametaphosphate, sodium alginate, and sodium lignosulfonate on the separation of magnesite and dolomite was poor. Meanwhile, the synergistic effect of acid etching with sodium carboxymethyl cellulose (CMC) could regulate the flotation separation of magnesite and dolomite over a wide pH range. Moreover, the synergistic effect of acid etching and CMC increased the flotation difference between magnesite and dolomite from 15.73% to 67.17%, and the selective separation index increased from 1.38 to 2.89. Characterization by atomic force microscopy revealed that acid etching altered the surface morphology of magnesite and dolomite, roughening their surfaces. Contact angle measurements, Fourier transform infrared spectroscopy analysis, and zeta potential measurements indicated that the synergistic effect of acid etching and CMC changed the wettability, charge, and adsorption performance of dolomite, selectively inhibiting the adsorption of NaOL onto the surface of dolomite, thereby inhibiting dolomite flotation. However, it has minimal effect on the floatability of magnesite. [ABSTRACT FROM AUTHOR]

This study aimed to determine the suitable reclamation ways of post‐mining magnesite. It was hypothesized that adding amendments and planting would decrease pH, increasing the nutrient availability and enhancing the soil microbial activity. Treatments included 200 g gypsum, 2 kg goat manure, and 200 g sulfur per square meter. Cedar (Cedrus libani A. Rich.), black locust (Robinia pseudoacacia L.), black pine (Pinus nigra J.F. Arnold), and sainfoin (Onobrychis sativa L.) were planted. Before and after the treatments, samples were taken from each experimental unit and analyzed. Analysis of the data indicated that the pH had decreased by 0.6 and 0.5 units on the gypsum + sulfur‐ and gypsum + manure‐treated experimental units, respectively, compared to the other treated plots. In addition, using manure significantly increased the organic matter N, P, and K content, by 3‐fold, 2.5‐fold, 7.5‐fold, and 2.5‐fold, respectively, and enhanced microorganism activity. The sulfur + manure treatment increased microbial C and N approximately twofold. Because the manure, sulfur, and gypsum treatments improved the tailings conditions for plant growth, the use of these amendments for mine tailing reclamation was strongly recommended. Across all treatments, cedar and black pine demonstrated 83 and 77% survival rates for the first 3 years of afforestation, respectively. For the same period, the black locust survival rate was 35% lower than that of the other species. The gypsum + manure application increased seedling height growth by about 20% for all three species compared to the other treatments. [ABSTRACT FROM AUTHOR]

The large-scale mining of magnesite generates substantial quantities of magnesite mine tailings (MMT), which pose a significant threat to soil, water, and air quality. Utilising cement-treated MMT as a subgrade material presents a promising solution to address this environmental challenge. However, the existing mechanical-empirical design methods cannot be directly employed due to the uncertainties associated with the various design parameters particularly the behaviour of cemented MMT. This research introduces a novel reliability-based MEM design method to design flexible pavements incorporating cemented MMT as subgrade. A three-layered flexible pavement configuration, with a middle granular layer sandwiched between the top bituminous layer and the bottom stabilised subgrade, was examined. The response surface model and finite element model were developed to determine the fatigue and rutting strains of the pavement. Monte Carlo simulation was adopted to compute reliability. Further, a sensitivity analysis was performed to probe the contribution of input parameters on the reliability of pavement. The developed methodology was illustrated with a case study. Reliability analysis revealed that the cemented MMT pavement achieved reliabilities of 97.44% and 96.27% for fatigue and rutting criteria, respectively, under a design traffic load of 30 million standard axles (msa). Additionally, the sensitivity analysis identified the modulus of elasticity of the granular layer and bituminous layer as the most critical input variables. Thus, the developed design methodology for pavements incorporating MMT enables the engineers to design MMT-based flexible pavements considering the uncertainties. [ABSTRACT FROM AUTHOR]

Flotation separation of magnesite and its calcium-containing carbonate minerals is a difficult problem. Recently, new regulators have been proposed for magnesite flotation decalcification, although traditional regulators such as tannin, water glass, sodium carbonate, and sodium hexametaphosphate are more widely used in industry. However, they are rarely used as the main regulators in research because they perform poorly in magnesite and dolomite single-mineral flotation tests. Inspired by the limonite presedimentation method and the addition of a regulator to magnesite slurry mixing, we used a tannin pretreatment method for separating magnesite and dolomite. Microflotation experiments confirmed that the tannin pretreatment method selectively and largely reduces the flotation recovery rate of dolomite without affecting the flotation recovery rate of magnesite. Moreover, the contact angles of the tannin-pretreated magnesite and dolomite increased and decreased, respectively, in the presence of NaOl. Zeta potential and Fourier transform infrared analyses showed that the tannin pretreatment method efficiently hinders NaOl adsorption on the dolomite surface but does not affect NaOl adsorption on the magnesite surface. X-ray photoelectron spectroscopy and density functional theory calculations confirmed that tannin interacts more strongly with dolomite than with magnesite. [ABSTRACT FROM AUTHOR]

Natural impurities such iron, sulphates, chlorides, and heavy metals that cannot be removed by recrystallization are present in the magnesia that is formed. One method for making magnesium perchlorate includes combining per chloric acid and magnesite dust, a process that generates a lot of heat and hydrogen gas during the reaction. Magnesite is leached using an aqueous per chloric acid solution with a 500 rpm stirring speed. The following factors were taken into account in this study: fluctuation in leaching temperature (°K), per chloric acid volume percentage, and time of leaching. Magnesium perchlorate recovery is 97.3% with a temperature increase to 333.15 K and 100% with an increase in leaching time to 1 h. Dehydration of magnesium chloride was tried through thermochemical processing with several compounds and the results are not encouraging. Experimental studies have also been carried out on the electrochemical preparation of magnesium hydroxide from magnesium chloride. [ABSTRACT FROM AUTHOR]

We present a carbonation-assisted flotation method for nickel (Ni) separation from low-grade ultramafic ores. The high process economics of conventional flotation of low-grade ultramafic ores makes Ni unrecoverable on an industrial scale. Based on the fundamentals of CO2 sequestration in minerals, we carbonated a low-grade serpentine (lizardite) ore specimen under extreme conditions (185 °C, 15 MPa, and 24 h) and attained a conversion efficiency of serpentine to magnesite of 22% and 16% in the presence and absence of inorganic salts, respectively. Rhombohedral structures on carbonated particles detected using scanning electron microscopy suggested the formation of magnesite. We also found that Ni–Fe existed as sulfides, as confirmed by elemental mapping micrographs, and did not leach out as Ni2+ and Fe2+, as confirmed through carbonation supernatant analysis. Here, we introduced Denver cell froth flotation experiments after carbonation, which showed that the carbonated ore in the presence of inorganic salts had 29% higher Ni recovery and 0.15 wt% higher nickel grade than the uncarbonated ore. This study is the first to successfully show that the carbonation of serpentine containing nickel-bearing pentlandite leads to magnesite formation, does not lead to the dissolution of nickel sulphide, and enhances the nickel separation efficiency during froth flotation. This study paves the path forward for the integration of mineral carbonation in the processing of low-grade ultramafic nickel ores. [ABSTRACT FROM AUTHOR]

Regolith-hosted Ni-Cr prospects in the Nkonko serpentinized massif are located near Kananga city in the Democratic Republic of Congo (DRC). This serpentinized massif displays an underground regolith profile divided into three main layers: (1) unweathered serpentinite bedrock, (2) saprolite serpentinites, and (3) the pedozone top layer. The bedrock serpentinites consist of serpentine (including lizardite and antigorite "garnierite") as a major phase, with Cr-spinel and magnetite as a subsidiary phase. The rock contains rare pseudo-olivine relicts. Saprolite serpentinites contain serpentines (e.g., lizardite, chrysotile, antigorite "garnierite") and subordinate ferrochromite and Cr-magnetite. These saprolite serpentinites are crosscut by veins of "garnierite" phase, talc, brucite, magnetite, magnesite, and chlorite. The pedozone primarily consists of lateritic soils with red and yellow limonite. Saprolite serpentinites exhibit relatively higher Al2O3, FeO, Fe2O3, and volatiles (LOI: loss on ignition) compared to bedrock serpentinites, while maintaining similar SiO2 contents. For trace elements, saprolite serpentinites contain elevated Cr (up to 5.4 wt%) and Ni (up to 2.0 wt%) compared to bedrock samples (Cr up to 0.9 and Ni up to 0.3 wt%). The REE concentrations are low (total REE of about 2.0 ppm) and remain unchanged between the saprolites and bedrocks. Spinel is identified as the main host mineral for Cr, while secondary serpentine "garnierite" is the primary host phase for Ni. Plots of Al2O3/SiO2 versus MgO/SiO2 for bedrock and saprolite serpentinites, along with the REE patterns, suggest that the serpentine regolith originated from the alteration and weathering of harzburgite. [ABSTRACT FROM AUTHOR]