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Precipitation experiments from a model Europan ocean solution subjected to fast and slow freezing suggest that the highly hydrated Na–Mg sulfate phase Na2Mg(SO4)2·16H2O is one of the lowest-temperature mineral phases likely to be stable on Europa’s surface and may therefore be astrobiologically significant., The precipitation of hydrated phases from a chondrite-like Na–Mg–Ca–SO4–Cl solution is studied using in situ synchrotron X-ray powder diffraction, under rapid- (360 K h−1, T = 250–80 K, t = 3 h) and ultra-slow-freezing (0.3 K day−1, T = 273–245 K, t = 242 days) conditions. The precipitation sequence under slow cooling initially follows the predictions of equilibrium thermodynamics models. However, after ∼50 days at 245 K, the formation of the highly hydrated sulfate phase Na2Mg(SO4)2·16H2O, a relatively recent discovery in the Na2Mg(SO4)2–H2O system, was observed. Rapid freezing, on the other hand, produced an assemblage of multiple phases which formed within a very short timescale (≤4 min, ΔT = 2 K) and, although remaining present throughout, varied in their relative proportions with decreasing temperature. Mirabilite and meridianiite were the major phases, with pentahydrite, epsomite, hydrohalite, gypsum, blödite, konyaite and loweite also observed. Na2Mg(SO4)2·16H2O was again found to be present and increased in proportion relative to other phases as the temperature decreased. The results are discussed in relation to possible implications for life on Europa and application to other icy ocean worlds.

Hygroscopic salts at Mars' near-surface (MgSO(4), (per)chlorates, NaCl) may form brines by absorbing moisture from the atmosphere at certain times through the process of deliquescence. We have previously shown strong bacterial growth in saturated MgSO(4) (∼67% w/v as epsomite) at room temperature, and growth was observed at the MgSO(4) eutectic point (43% w/v at -4°C). Here, we have investigated the growth of salinotolerant microbes (Halomonas, Marinococcus, Planococcus) from Hot Lake, Washington; Basque Lake, British Columbia; and Great Salt Plains, Oklahoma under deliquescing conditions. Bacterial cultures were grown to mid-log phase in SP medium supplemented with 50% MgSO(4) (as epsomite), 20% NaClO(3), or 10% NaCl (w/v), and small aliquots in cups were dried by vacuum desiccation. When the dried culture was rehydrated by the manual addition of water, the culture resumed growth in the reconstituted brine. When desiccated cultures were maintained in a sealed container with a brine reservoir of the matching growth medium controlling the humidity of the headspace, the desiccated microbial culture evaporites formed brine by deliquescence using humidity alone. Bacterial cultures resumed growth in all three salts once rehydrated by deliquescence. Cultures of Halomonas sp. str. HL12 showed robust survival and growth when subjected to several cycles of desiccation and deliquescent or manual rehydration. Our laboratory demonstrations of microbial growth in deliquescent brines are relevant to the surface and near-subsurface of cold arid worlds like Mars. When conditions become wetter, hygroscopic evaporite minerals can deliquesce to produce the earliest habitable brines. Survival after desiccation and growth in deliquescent brines increases the likelihood that microbes from Earth, carried on spacecraft, pose a contamination risk to Mars.

In this investigation, the coal fires in different Colombian coal mines were studied using advanced electron beam and X-ray diffraction techniques. The results were compared with information from high-resolution transmission electron microscopy (HR-TEM) equipped with a dispersive X-ray detector (EDS). Amorphous phases, salammoniac, anatase, muscovite, goethite, jarosite, calcite, gypsum, kaolinite, illite, and quartz are the dominant mineral matter constituents in almost all of the coal fires, with minute quantities of native sulfur, magnetite, siderite, pyrite, pickeringite, epsomite, hexahydrite, halotrichite being present in around half of the investigated coal fire samples. Other minerals that are present in some particular samples are chlorite, ankerite, and dolomite. Fe-sulfides were also detected particularly in the pyrite-bearing coal fires, possibly indicating oxidation of the Fe-sulfides occurring with coal fires. Exhaust discharge data indicate an overall trend of reducing carbon dioxide (CO2) and carbon monoxide (CO) releases (between 1.5 and 34%) from the coal fires. This is the first report on Colombian coal fires, which would be important for different perspectives of the research in the area.

Marine Mg-evaporites are a small oceanic sink of magnesium, precipitating only from extremely evaporated brines. The isotopic composition of Mg in seawater, δ26Mgseawater, has recently been shown to be an effective tool for reconstructing the Mg budget of the modern and past oceans. However, estimations of the Mg isotope fractionation between the Mg-evaporites and their precipitating solution are required for full quantification of the isotope effect of the evaporitic sink on δ26Mgseawater, as well as for utilizing ancient evaporitic sequences as an archive for past δ26Mgseawater. Here, we estimate the Mg isotope fractionation between Mg-evaporites and modern marine-derived brine along the course of seawater evaporation, up to degree evaporation of >200. The sequence of Mg-salts included epsomite (MgSO4·7H2O), kainite (KMgClSO4·3H2O), carnallite (KMgCl3·6H2O), kieserite (MgSO4·H2O) and bischofite (MgCl2·6H2O). The following isotope fractionation values, either negative or positive, were calculated from the isotope difference between the salt and its precipitating brine, and from the evolution of δ26Mg in the brine throughout the evaporation: Δcarnallite-brine = +1.1‰, Δepsomite-brine = +0.59‰, Δbischofite-brine = +0.33‰, Δkieserite-brine = −0.2‰ and Δkainite-brine = −1.3‰. Magnesium isotopic compositions determined on minerals from different ages in the geological record corroborate well these results. Due to precipitation of multi-mineral assemblages having isotope fractionation values of opposing signs, the δ26Mg value of the brine changes only slightly (50%). The isotope fractionations are shown to correlate with the number of water molecules coordinated to the Mg2+ and with Mg-O bond length in the mineral lattice. Given these isotope fractionations, it is calculated that a volume of 0.4 · 106–0.8 · 106 Km3 of a mono-mineral assemblage of kainite or carnallite needs to precipitate in order to change seawater δ26Mg by only 0.1‰. This huge volume is by far larger than the volume of these minerals known to date in the global geological record. Therefore, it is concluded that the impact of Mg-evaporites formation on δ26Mgseawater has been insignificant since the Proterozoic. The results of this study suggest that the Mg isotopic composition of Mg-evaporites preserved in the geological record of evaporitic basins may be used to: 1) quantify geochemical processes that fractionate Mg-isotopes within these basins, such as dolomitization; and 2) complete the secular variations curve of the marine δ26Mg record using basins with well-established evaporitic sequences., Geochimica et Cosmochimica Acta, 301, ISSN:0016-7037, ISSN:1872-9533

The solubility isotherms of the two ternary systems (MgSO4 + MgB4O7 + H2O(and (MgSO4+ Mg2B6O11+H2O) were determined using the isothermal dissolution equilibrium method at 273.15 K and 288.15 K. Solubilities and acidities of the liquid phase were determined in detail experimentally. According to the experimental data, the phase diagrams for two ternary systems were given. The results indicate that the two ternary systems are the simple saturated type, and double salt or solid solution are not formed. There are one invariant point corresponding to (epsomite + hungchaoite or inderite), two isothermal dissolution curves, and two crystallization regions in two ternary systems. It was found that the crystallization region areas of magnesium borate were larger than that of epsomite, indicating that the solubility of epsomite was larger in the two systems. The presence of magnesium sulfate can prevent the transformation of hungchaoite into inderite, and magnesium sulfate has a significant solubilizing effect on both magnesium borate at the experimental temperature. The distributions of polyborate species in saturated magnesium borate solution varying with mass fraction of magnesium sulfate were calculated by the Newton iteration method.

An in-depth scientific survey revealed the deterioration mechanisms affecting the ‘Santa Maria della Stella’ church in Saluzzo, Italy, where various salt crystallization processes are strongly damaging the building materials and artworks. Rainwater seepage permeates the vault and interior, causing: (1) epsomite growth as interstitial columnar crystals (resulting in pictorial coating detachment) or superficial, powdery efflorescence; (2) formation of nesquehonite/hydromagnesite crusts on wall paintings; and (3) nitratine growth causing pigment staining and detachment. These processes involve selective Mg2+ mobilization from magnesian-lime mortars and bacterial-induced formation of nitrates from guano, with consequent precipitation of degrading salts. The study confirms how characterization of all deterioration agents is fundamental to planning a viable cultural heritage conservation and restoration programme.

Extracting valuable salts from reverse osmosis reject brine may be a solution to reduce environmental risk of this effluent if discarded. Isothermal evaporation (25°C) allows recovering many salts like gypsum, halite, and magnesium salts (epsomite, hexahydrite). In this paper, magnesium sulfate crystallization was studied, for this purpose two different quinary diagrams were used to draw the crystallization path. Furthermore, the application of Pitzer model and the use of Phreeqc program were required, respectively, to calculate electrolytes solubility product and to simulate the evaporation steps. Experimentally, X-ray diffraction was adopted to identify the nature of recovered solid phases. The different results of this study are almost similar and confirm the crystallization of epsomite and hexahydrite at the end of evaporation process.

In the period 1969-1973 two experiments were performed in young orchards in Central Poland: a four-year experiment at Julianów, on sandy loamy soil on underlying sand and one-year experiment at Kośmin, on sandy loam soil on clay loam. At Kosmin, in spite of a high Mg content in the subsoil, Mg deficiency symptoms appeared, because of shallow rooting owing to poor aeration. In both experiments, foliar sprays with epsomite were less effective than fertilization to the soil; at Kośmin even eight sprays were less effective than soil dressings. Mg losses from a sandy soil due to leaching were high, particularly where sand was present in the whole profile; under these conditions the least losses of Mg were from split doses of epsomite (Mg3x120). Single doses of epsomite were the most effective in increasing leaf Mg content, reducing Mg deficiency symptoms and promoting growth of trees in the first year after application; in the later years split doses of epsomite and a single initial dose of magnesium lime were more effective. Effects of Mg fertilization on growth and yields of apples were rather slight, when K fertilizer doses were low. No effect of Mg fertilization upon fruit drop and fruit quality was found. Preliminary recommendations for practice are given.

Supplementary data related to this article can be found at https://doi.org/10.1016/j.chemosphere.2018.04.095., Rare earth elements (REE) were analyzed in river waters, acid mine waters, and extracts of secondary precipitates collected in the Iberian Pyrite Belt. The obtained concentrations of the REE in river water and mine waters (acid mine drainage - AMD) were in the range of 0.57 μg/L (Lu) and 2579 μg/L (Ce), which is higher than previously reported in surface waters from the Iberian Pyrite Belt, but are comparable with previous findings from AMD worldwide. Total REE concentrations in river waters were ranged between 297 μg/L (Cobica River) and 7032 μg/L (Trimpancho River) with an average of 2468 μg/L. NASC (North American Shale Composite) normalized REE patterns for river and acid mine waters show clear convex curvatures in middle-REE (MREE) with respect to light- and heavy-REE. During the dissolution experiments of AMD-precipitates, heavy-REE and middle-REE generate the most enriched patterns in the solution. A small number of precipitates did not display MREE enrichment (an index Gdn/Lun, Financial support was provided by the Andalusian Autonomous Government Excellence Project, code P06-RNM-02167. This work was also co-funded by the European Union through the European Regional Development Fund, based on COMPETE 2020, project ICT (UID/GEO/04683/2013), reference POCI-01-0145-FEDER-007690, national funds provided by FCT. Post-Doctoral Fellowship through Erasmus Mundus SAT program and Young Scientist Research Grant (SEAS-2015−14) of the National University of Mongolia were supported for T.-O. Soyol-Erdene. The authors also appreciate the valuable comments and suggestions made by the anonymous reviewers.

Symptoms of Mg deficiency on apple trees in the Warsaw district, Central Poland are described and illustrated. Results of soil and leaf analyses of deficient and healthy trees and factors affecting Mg deficiency in apples are discussed. Mg deficiency was found mainly in young trees grown on light, sandy or sandy loamy grey-brown podsolic soils; an old trees it was very rare, because of deep root penetration and utilization of Mg from illuvial horizons rich in Mg. Severe Mg deficiency symptoms appeared on old trees, vigorously growing after topworking with Bancroft scions. Low soil and leaf of Mg content a high available potassium to magnesium ratio in the soil and high ratio in the leaves are suggested to be important factors promoting Mg deficiency symptoms. A three years' experiment run on old Bancroft apple trees showed that 400 kg of MgO applied in epsomite to the soil were as effective as 4 sprays of 2% epsomite. Soil or foliar Mg fertilization did not have any significant effect on tree growth, yields, fruit drop and fruit quality.

The alteration mineralogy in the crater area of Poás volcano (Costa Rica) has been studied to constrain acid fluid-rock interaction processes and conditions relevant for the formation of sulphate-bearing mineral assemblages found on the surface of Mars. Individual sub-environments, which include the hyperacid lake (Laguna Caliente), ephemeral hot springs, fumarole vents and areas affected by acid rain and/or spray from the lake, are marked by distinct secondary mineral associations, with sulphates commonly as prevailing component. The sulphates occur in a wide mineralogical diversity comprising gypsum/anhydrite, various polyhydrated Al-sulphates, alunite-jarosite group minerals, halotrichite-, voltaite- and copiapite-group minerals, epsomite and römerite. Depending on the sub-environment, they are variably associated with clay minerals (kaolinite-group and smectite-group), zeolites, SiO2-polymorphs, Fe-(hydro)oxides, Ti-oxides, native sulphur, sulphides, chlorides, fluorides, phosphates and carbonates. Geochemical modelling was performed to identify mechanisms responsible for the formation of the secondary minerals found in the field, and to predict their possible stability under conditions not seen at the surface. The results indicate that the appearance of amorphous silica, hematite, anhydrite/gypsum, pyrite, anatase and kaolinite is relatively insensitive to the degree of acidity of the local aqueous system. On the other hand, alunite-jarosite group minerals, elemental sulphur and Al(OH)SO4 only form under acidic conditions (pH < 4). The presence of polyhydrated Mg- and Fe2 +-sulphates is restricted to olivine-bearing rocks exposed to acid rain or brine spray. Modelling suggests that their formation required a repetitive sequence of olivine dissolution and evaporation in an open system involving limited amounts of fluid. The mineral variety in the crater of Poás is remarkably similar to sulphate-bearing assemblages considered to be the product of acid-sulphate alteration on Mars. The analogy suggests that comparable fluid-rock interaction controls operated in Martian volcanic environments.

An apparatus for the compression of materials to ∼2 GPa and subsequent rapid chilling to 80 K with extraction to ambient pressure is described. The partial resolution of a long-standing problem concerning the high-pressure phase behaviour of a water-rich salt hydrate is demonstrated using the equipment., An apparatus is described for the compression of samples to ∼2 GPa at temperatures from 80 to 300 K, rapid chilling to 80 K whilst under load and subsequent recovery into liquid nitro­gen after the load is released. In this way, a variety of quenchable high-pressure phases of many materials may be preserved for examination outside the high-pressure sample environment, with the principal benefit being the ability to obtain high-resolution powder diffraction data for phase identification and structure solution. The use of this apparatus, in combination with a newly developed cold-loadable low-temperature stage for X-ray powder diffraction (the PheniX-FL), is illustrated using ice VI (a high-pressure polymorph of ordinary water ice that is thermodynamically stable only above ∼0.6 GPa) as an example. A second example using synthetic epsomite (MgSO4·7H2O) reveals that, at ∼1.6 GPa and 293 K, it undergoes incongruent melting to form MgSO4·5H2O plus brine, contributing to a long-standing debate on the nature of the high-pressure behaviour of this and similar highly hydrated materials. The crystal structure of this new high-pressure polymorph of MgSO4·5H2O has been determined at 85 K in space group Pna21 from the X-ray powder diffraction pattern of a sample recovered into liquid nitro­gen and is found to differ from that of the known ambient-pressure phase of MgSO4·5H2O (pentahydrite, space group ), consisting of corner-sharing MgO6–SO4 ion pairs rather than infinite corner-sharing chains.

Water vapour sorption in salt hydrates is one of the most promising means of compact, low loss and long-term solar heat storage in the built environment. Among all, epsomite (MgSO4·7H2O) excels for its high-energy storage density and vast availability. However, in practical applications, the slow kinetics and evident structural changes during hydration and dehydration significantly jeopardise the heat storage/recovery rate. A molecular dynamics (MD) study is carried out to investigate the thermal properties and structural changes in the thermal dehydration process of the epsomite. The MD simulation is carried out at 450 K and a vapour pressure of 20 mbar, in accordance with experimental heat storage conditions. The study identifies the dehydration as multiple stages from the initial quick water loss and collapse of the crystal framework to the adsorption of water molecules, which inhibits complete dehydration. Further, the anisotropic diffusion behaviour supports the important role of the porous matrix structure in the heat and mass transfer process. The enthalpy changes, partial densities, mass diffusion coefficients of water and radial distribution functions are calculated and compared with corresponding experimental data to support the conclusions.

An exceptional new occurrence of the mineral tamarugite, NaAl(SO 4 ) 2 · 6H 2 O, from a short karst cavity (Diana Cave, Baile Herculane; SW Romania) is described. It was formed by corrosion of the bedrock (limestone and marls) by a SO 4 2− -rich steam condensate resulting from oxidized S 2− ions escaping from the thermo-mineral water emerging from depth in the cave. Tamarugite forms dull white earthy aggregates. Scanning-electron microscope (SEM) observations reveal tabular subhedral crystals never exceeding 15 μm across. The cell parameters refined from the powder data for the monoclinic space group P 2 1 / a are: a = 7.358(6), b = 25.23(2), c = 6.093(5) A, β = 95.16(5) °, V = 1126.98(1) A 3 . The δ 34 S values of the cave sulphates and the thermal water confirm marine evaporites as the source of sulphur. The sulphate-acid alteration of limestone with contribution of Al 3+ and Na + from the marls and the thermal water is responsible for the formation of tamarugite. The steam-condensate alteration paragenesis includes native sulphur, bassanite, anhydrite, epsomite, pickeringite, halotrichite, apjohnite and alunite, as well as quartz and halite, all primary and secondary speleogenetic by-products.

We investigate two poly-hydrated magnesium sulfates, hexahydrite (MgSO4 · 6H2O) and epsomite (MgSO4 · 7H2O), in the visible and infrared (VNIR) spectral range 0.5/4.0 μm, as particulate for three different grain size ranges: 20-50 μm, 75-100 μm and 125-150 μm. All samples were measured in the 93-298 K temperature range. The spectra of these hydrated salts are characterized by strong OH absorption bands in the 1.0-1.5 μm region, and by H2O absorption bands near 2 and 3 μm. Other weak features show up at low temperatures near 1.75 μm (in both hexahydrite and epsomite) and 2.2 μm (only in hexahydrite). The spectral behavior of the absorption bands of these two minerals has been analyzed as a function of both grain size and temperature, deriving trends related to specific spectral parameters such as band center, band depth, band area, and band width. Hydrated minerals, in particular mono- and poly-hydrated sulfates, are present in planetary objects such as Mars and the icy Galilean satellites. Safe detection of these minerals shall rely on detailed laboratory investigation of these materials in different environmental conditions. Hence an accurate spectral analysis of such minerals as a function of temperature is key to better understand and constrain future observations.

Recent satellite inferences of hydrous sulfates as recurrent minerals on the surface of icy planetary bodies link with the potential mineral composition of their interior. Blodite, a mixed Mg-Na sulfate, is here taken as representative mineral of icy satellites surface to investigate its crystal structure and stability at conditions of the interior of icy bodies. To this aim we performed in situ synchrotron angle-dispersive X-ray powder diffraction experiments on natural blodite at pressures up to ∼10.4 GPa and temperatures from ∼118.8 K to ∼490.0 K using diamond anvil cell technique to investigate the compression behavior and establish a low-to-high temperature equation of state that can be used as reference when modeling the interior of sulfate-rich icy satellites such as Ganymede. The experimentally determined volume expansivity, α, varies from 7.6 (7) 10−5 K−1 at 0.0001 GPa (from 118.8 to 413.15 K) to 2.6 (3) 10−5 K−1 at 10 GPa (from 313.0 to 453.0 K) with a δα/δP coefficient = −5.6(9)10−6 GPa−1 K−1. The bulk modulus calculated from the least squares fitting of P-V data on the isotherm at 413 K using a second-order Birch - Murnaghan equation of state is 38(5) GPa, which gives the value of δK/δT equal to 0.01(5) GPa K−1. The thermo-baric behavior of blodite appears strongly anisotropic with c lattice parameter being more deformed with respect to a and b. Thermogravimetric analyses performed at ambient pressure showed three endotherms at 413 K, 533 K and 973 K with weight losses of approximately 11%, 11% and 43% caused by partial dehydration, full dehydration and sulfate decomposition respectively. Interestingly, no clear evidence of dehydration was observed up to ∼453 K and ∼10.4 GPa, suggesting that pressure acts to stabilize the crystalline structure of blodite. The data collected allow to write the following equation of state, V(P, T) = V0[1 + 7.6(7)10 − 5ΔT − 0.026(3)P − 5.6(9)10 − 6PΔT−6.6(9)10 − 6PΔT)] from which the density of blodite can be determined at conditions of the mantle of the large icy satellites of Jupiter. Blodite has higher density, bulk modulus and thermal stability than similar hydrous sulfates (e.g. mirabilite and epsomite) implying, therefore, a different contribution of these minerals to the extent of deep oceans in icy planets and their distribution over the local geotherms.

Mestrado em Engenharia Geológica - Recursos Geológicos Sulfato de Magnésio, sob forma de Cristais, principalmente de Epsomite, a partir de Água Mãe. A Água Mãe é proveniente de Salinas, em particular da Salina de Santiago da Fonte. Do Cristalizador da mesma foram recolhidas amostras de Lama. Para além disso foi recolhida Argila Ilítica, num terreno em obras, nas imediações do Campus Universitário, da Universidade de Aveiro. A Argila e a Lama recolhidas tinham como objetivo formar um “substrato” juntamente com a Água Mãe, que fomentasse a precipitação e a formação dos Cristais. Primeiramente, tanto a Lama como a Argila foram estudadas a nível de Perda de Água, conforme tinham sido recolhidas em campo. A Argila foi misturada com a Água Mãe, assim como a Lama. Desse modo, formaram-se Polpas que foram Refinadas/beneficiadas e Separadas, usando um equipamento apropriado para o efeito, através de elutriação e flutuação natural, por forma a serem obtidos materiais “Overflow” e “Underflow”, tanto para a Polpa contendo Lama, como para a Polpa contendo Argila. Ambas foram vertidas em recipientes, tabuleiros e provetas para ser visualizada a formação de Cristais. Para além do processo de Refinação/beneficiação e Separação, houve também Separação Granulométrica por via húmida através de peneiração e Separação Granulométrica da fração fina através do aparelho Sedigraph. Os Cristais formados através das Polpas foram analisados por Difração de Raios X, para se conhecer a sua composição mineralógica. A Água Mãe foi analisada do ponto de vista químico. Foram também analisados, por Difração de Raios X, alguns Cristais que se formaram na Água Mãe. De acordo com cálculos e análises efetuadas, foi possível concluir que a Perda de Água foi mais rápida na Argila do que na Lama. A amostra usada para Refinação/beneficiação e Separação de Lama contém maior Fração de Água, Peso de Água e Diluição do que a amostra usada para Refinação/beneficiação e Separação da Argila. Os pesos específicos das Polpas distribuídas nos tabuleiros b) e nos recipientes a)F apresentam valores mais baixos do que as restantes Polpas. A Polpa referente à “Lama Primavera” “Overflow” é a que contém maior percentagem de partículas finas. Os Cristais formados a partir da Água Mãe são os únicos que contêm evidências de Sulfato de Magnésio, principalmente no Cristal “C1” (presença de Hexahydrite e Bloedite) e no “C2” (presença de Hexahydrite e Kieserite). No Cristal “C3” existem evidências de Cloreto de Magnésio Hidratado (Bischofite). Relativamente à análise química da Água Mãe, os valores de pH são ligeiramente ácidos e os valores de Condutividade são mais baixos do que o esperado. Por fim, os valores da concentração de Magnésio, em (mg/l), na Água Mãe, são altos. The objective of this work is the study of the precipitation of Magnesium Sulfate salts, in Crystals’ form, mainly of Epsomite, from Mother Water. The Mother Water comes from Salt Pans, in particular from the Salt Pan of Santiago da Fonte. Samples of Mud were collected from the Cristallizer of that Salt Pan. In addition, Illitic Clay was collected from a formation under construction, near the University Campus of Aveiro. The collected Clay and Mud were intended to form a “substrate” once mixed with the Mother Water, which would promote Crystals’ precipitation and formation. Firstly, both Mud and Clay were studied at the level of Water Loss, as the same way they were found and collected on the formation. The Clay was mixed with the Mother Water, as well as the Mud. Thus, there was a formation of Pulps, which were Refined/beneficiated and Separated, using an appropriate equipament for this purpose, through elutriation and natural flotation, in order to obtain ”Overflow” and “Underflow” materials, both for the Pulp containing Mud as for the Pulp containing Clay. Both were poured into containers, trays and test tubes in order to visualize the formation of Crystals. After the Refining/beneficiation and Separation process there was also wet Granulometric Separation through sieving and Granulometric Separation of the fine fraction through the Sedigraph apparatus. Crystals formed through the Pulps were analyzed by X Ray Diffraction to know their mineralogical composition. The Mother Water was analyzed from chemical point of view. Some Crystals that were formed in the Mother Water were also analyzed by X Ray Diffraction. According to calculations and analyses, it was possible to conclude that the Water Loss was faster in the Clay than in the Mud. The Sample used for Refining/beneficiation and Separation of Mud contains higher Water Fraction, Water Weight and Dilution than the Sample used for Refining/beneficiation and Separation of Clay. The Specific Weight of the Pulps distributed in trays b) and in the containers a)F present lower values than the other Pulps. The Pulp referring to the “Spring Mud” “Overflow” is the one that contains higher percentage of fine particles. The Crystals formed from the Mother Water are the only ones that contain evidence of Magnesium Sulfate, mainly in Crystal “C1” (presence of Hexahydrite and Bloedite) and “C2” (presence of Hexahydrite and Kieserite). In the Crystal “C3”, there is evidence of Hydrated Magnesium Chloride (Bischofite). Regarding to the chemical analysis of the Mother Water, the pH values are slightly acidic and the Conductivity values are lower than expected. Finally, Magnesium concentration values (mg/l) in the Mother Water are high.

Epsomite (MgSO4.7H2O) is a hydrogen bonded crystal having a wide range of applications in various fields. Pure and glycine added Epsomite (a total of six) single crystals have been grown and characterized in order to investigate the effect of glycine as an impurity on the properties of Epsomite crystals.The densities and lattice parameters observed indicate that the impurity molecules have entered into the crystal matrix. The grown crystals exhibit good optical transparency in the wavelength range 210-1100 nm. Second harmonic generation measurements indicate that they are nonlinear optically active. Results obtained through microhardness measurements follow the normal indentation size effect. Electrical (AC and DC) measurements indicate that all the six crystals grown in the present study exhibit a normal dielectric behavior and the electrical conduction is understood to be due to the protonic movement. Moreover, glycine addition is found to reduce er value significantly indicating the possibility of Epsomite crystal becoming a low -er value

Fossil materials that contain iron sulfide are well known for their instability when exposed to oxygen and humidity. This term however combines a great variety of materials showing different types of damages. Most of them consist of crystal efflorescence appearing on the surface and inside the matrix. In this work, a methodology was determined for the analysis of these damages by the use of Raman and infrared spectroscopy. The infrared and Raman signatures of a large set of iron sulfates were characterized. Specific attention was paid to sideronatrite and ferrinatrite, which are two associated sodium/iron(III) sulfates, and their infrared and Raman bands were partially assigned. Analysis performed on a selection of 11 damaged fossils showed a great variety of degradation products: besides one case that appeared to be a synthetic resin close to polyvinylchloride acetate, which was applied with a brush on the fossil surface, all degradation products belong to the sulfate group. However, many iron-free sulfates, such as gypsum, halotrichite, epsomite, or pentahydrite were found, often in association with iron sulfates. In one case, despite the presence of iron in the matrix, no iron sulfate could be detected. This shows that the term ‘pyritic fossil’, commonly used by collection managers, is not appropriate as it oversimplifies the reality. A name such as ‘sulfide-containing fossil’ would be more suitable. Copyright © 2012 John Wiley & Sons, Ltd.

In situ X-ray diffraction (XRD) and environmental scanning electron microscope (ESEM) crystallization experiments show oriented growth of magnesium sulfate crystals on a diethylenetriaminepenta- methylene phosphonic acid (DTPMP) template adsorbed onto Iceland spar (calcite, CaCO3) cleavage surfaces. Epsomite (MgSO4·7H2O) and hexahydrite (MgSO4·6H2O) crystallize (depending on the ambient conditions) in the presence of DTPMP with (010)epsomite//(101¯4)calcite and (1¯11)hexahydrite//(101¯4)calcite, whereas in the absence of DTPMP they show no preferred orientation. On the other hand, sodium sulfate (mirabilite, Na2SO4·10H2O) nucleates onto a Ca- DTPMP precipitate with (001)mirabilite//(101¯4)calcite. In contrast, different sodium sulfate phases crystallize and grow with no preferred crystallographic orientation in the absence of an organic additive. These results allow us to propose a model for the interaction calcite-DTPMP-Na and Mg sulfates based on the template-assisted nucleation and oriented heterogeneous crystallization, mediated by a Ca-precipitate, of inorganic salts on calcitic substrates. This effect results in a (measured) reduction in the critical supersaturation reached by these salts when crystallizing in confined geometries, i.e., a pore, thus resulting in a reduction in crystallization pressure and damage to porous substrates such as building stones. These results have implications in fields where in-pore crystallization of salts results in damage or plugging of the porous network, e.g., cultural heritage conservation and in the oil industry, where phosphonates are used as crystallization inhibitors.

Ojo de la Reina is the first and the smallest cave intersected at the -290 level in the Naica Mine (Mexico), therefore it was the first cavity in which the lowering of temperature induced by mine ventilation caused condensation over crystals’ surface since 2005. The consequent dissolution of the gypsum crystals and subsequent condensed water evaporation lead to the deposition of several new minerals, among which some highly soluble Mg/Na compounds (bloedite, epsomite, halite, hexahydrite, kieserite, starkeyite). The single available source of Mg and Na ions in this minerogenetic environment is represented by the huge fluid inclusions widespread within the crystals. The condensation occurs mainly along the widened principal exfoliation (010) planes, and allows to an easy and fast opening of the fluid inclusions that consequently drip Mg-rich fluids stored inside them. Finally the evaporation of the relatively small volumes of involved water allows to the development of the high soluble Mg and Na compounds.

Solubility in the liquid–solid metastable system Li2SO4 + MgSO4 + Na2SO4 + H2O at T = 263.15 K was studied using the isothermal evaporation method. Based on experimental data, dry-salt phase and water-phase diagrams of the system were plotted. The dry-salt phase diagram of the system includes one three-salt co-saturation point, three metastable solubility isotherm curves, and three crystallization regions corresponding to lithium sulphate monohydrate (Li2SO4·H2O), epsomite (MgSO4·7H2O), and mirabilite (Na2SO4·10H2O). Neither a solid solution nor double salts were found. Based on the extended Harvie–Weare (HW) model and its temperature-dependent equation, the values of the Pitzer parameters β(0), β(1), β(2), and CΦ for Li2SO4, MgSO4, and Na2SO4, the mixed ion-interaction parameters θLi,Na, θLi,Mg, θNa,Mg, Ψ Li,Na,S O 4 , Ψ Li,Mg,S O 4 , and Ψ Na,Mg,S O 4 , and the Debye–Huckel parameter AΦ in the quaternary system at 263.15 K were obtained. The solubility of the quaternary system Li2SO4 + MgSO4 + Na2SO4 + H2O at T = 263.15 K was also calculated. A comparison between the calculated and experimental results shows that the predicted solubility agrees well with experimental data.

Since evaporitic rocks on the Martian surface could (or still can) serve as potential habitats for microbial life on Mars, there is a reasonable possibility that these rocks may sustain molecular remnants as evidence for the presence of extinct or extant living organisms on Mars and that beta-carotene could be a suitable biomarker. In this paper, Raman microspectrometry was tested as a nondestructive method of determining the lowest detectable beta-carotene content in experimentally prepared evaporitic matrices--namely, gypsum, halite and epsomite. Two excitation wavelengths were compared--514.5 nm, because of the resonance Raman enhancement in the carotenoid analysis, and 785 nm, as a more universal wavelength now much used in the detection of biomolecules terrestrially. Mixtures were measured directly as well as with a laser beam penetrating the crystals of gypsum and epsomite. We have obtained beta-carotene signals at the 0.1 to 10 mg kg(-1) level--the number of registered beta-carotene Raman bands differed depending on the particular mineral matrix and the excitation wavelength. Concentrations of beta-carotene of about one order of magnitude higher were identified when analysed through single crystals of gypsum and epsomite, respectively.

Since its abandonment 185 years ago, the XII century Santa Maria de Bonaval Monastery located in Guadalajara (Spain) has suffered significant deterioration: first the roof was lost, followed by partial collapse of the walls, moisture infiltration and extensive loss of stone surfaces due to salt weathering. This case study is a clear example of the incompatibility of some building materials: in this case, the combination of sulphate-bearing mortars and magnesium-rich stone and mortars leading to extensive weathering by magnesium sulphate crystallization. Samples of plaster, bedding and core mortars, stone fragments and flakes, salt crust and powders were collected, as well stone samples from the historic quarries located close to the Monastery. Characterization by XRD (X-ray diffraction), ESEM-EDS (environmental scanning electron microscopy with energy dispersive X-ray spectroscopy) shows that the most important stone-type used in the structure, dolostone, is mainly affected by magnesium sulphate salts (epsomite, MgSO4 · 7H2O), although other salts as kalicinite (KHCO3) and mercallite (KHSO4) were also detected. The connected porosity and pore size distribution determined by mercury intrusion porosimetry and capillarity behaviour suggest that the core mortar could easily be dissolved and the stone, plaster and bedding mortars are able to transport infiltrating solutions, giving rise to the precipitation of magnesium sulphate in the mortar joints and over the surface of the stone. Due to their chemical incompatibility, the combination of sulphate and magnesium-bearing mortars and stone with high magnesium content appears to be problematic and should be avoided in future restoration work. Ministry of Science and Technology JCCM, Toledo (Spain) and the European Social Fund; Spanish projects C.I.C.Y.T.-CGL2004-03564/BTE and MATERNAS-S-0505/MAT/000094.

The metastable solubilities and densities of the aqueous ternary system K2SO4+MgSO4+H2O at (288.15 and 308.15) K were determined with the isothermal evaporation method. Using the experimental results, the metastable phase diagram and the densities versus composition diagram were plotted. In the metastable phase diagrams of the ternary system at (288.15 and 308.15) K, there are in all two invariant points, three univariant solubility curves, and three metastable crystallization regions corresponding to arcanite (i.e., anhydrous potassium sulfate, K2SO4), picromerite (K2SO4⋅MgSO4⋅6H2O) and epsomite (MgSO4⋅7H2O) that are formed in the metastable equilibrium system. A comparison of the stable and metastable phase diagrams at each temperature shows that the metastable regions of magnesium sulfate are obvious, and the crystallizing regions of epsomite and arcanite are much larger than those in the stable phase diagram. The densities of the system changed regularly with the magnesium sulfate content. The resulting information can be used to recover potassium or remove magnesium. The calculated densities using an empirical equation agree well with the experimental results.

A number of phosphonates and carboxylates were tested as potential crystallization inhibitors for epsomite (MgSO4·7H2O). Epsomite nucleation is strongly inhibited in the presence of amino tri(methylene phosphonic acid) (ATMP), diethylenetriaminepentakis (methylphosphonic acid) (DTPMP), and poly(acrylic acid) sodium salt (PA). These additives also act as habit modifiers promoting the growth of acicular crystals elongated along the [001] direction. Environmental scanning electron microscopy (ESEM), Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), and molecular modeling of additive adsorption on specific epsomite (hkl) faces are used to identify how these additives inhibit epsomite crystallization. Additives attach preferentially on epsomite {110} faces, at edges of monolayer steps parallel to [001]. Step pinning and the eventual arrest of step propagation along ⟨110⟩ directions account for the observed habit change. Hydrogen bonding between the functional groups of additive mol...

The sulfur isotopic compositions of barite (BaSO4), anhydrite (CaSO4), gypsum (CaSO4·2H2O), mascagnite ((NH4)2SO4), thenardite (Na2SO4), boetite (K2SO4), epsomite (MgSO4·7H2O), magnesium sulfate (MgSO4·xH2O) and cysteine (an amino acid) were determined with a Cameca NanoSIMS 50 ion microprobe employing a Cs+ primary ion beam and measuring negative secondary ions. This ion microprobe permits the analysis of sulfur isotope ratios in sulfates on 0.001–0.5 ng of sample material, enabling the analysis of individual S-bearing particles with diameters as small as 500 nm. The grain-to-grain reproducibility of measurements is typically 5‰ (1σ) for micron-sized grains

Remote sensing observations and rover missions have documented the presence of sulphate-rich mineral associations on Mars. Many of these minerals are paleo-indicators of hydrous, acidic and oxidising environments that must have prevailed in Mars´ distant past, contrary to the present conditions. Furthermore, occurrences of silica together with high Cl and Br concentrations in Martian soils and rocks represent fingerprints of chemically atypical fluids involved in processes operating on the surface or at shallow depth. From field observations at representative active volcanoes in subduction settings, supported by geochemical modelling, we demonstrate that volcanic hydrothermal systems are capable of producing Mars-like secondary mineral assemblages near lakes, springs and fumaroles through the action of acidic fluids. Water–gas-rock interactions, together with localised flow paths of water and fumarolic gas emitted from associated subaerial vents, lead to deposition of a range of sulphates, including gypsum, jarosite, alunite, epsomite and silica. Evaporation, vapour separation and fluid mixing in (near-) surface environments with strong gradients in temperature and fluid chemistry further promote the diversity of secondary minerals. The mineralogical and chemical marks are highly variable in space and time, being subject to fluctuations in ambient conditions as well as to changes in the status of volcanic-hydrothermal activity. It is concluded that active processes in modern volcanic-geothermal systems may be akin to those that created several of the sulphate-rich terrains in the early history of Mars.

Salt hydrates have an active role in regolith development on Mars. The Mg-sulfate system, with highly variable values of n in the formula MgSO 4 · n H 2 O, is particularly subject to transformations among several crystalline and amorphous forms. The Ca-sulfate system, CaSO 4 · n H 2 O, is likely to be associated with the Mg-sulfates in most occurrences, but is less susceptible to transformations in n . Desiccation of MgSO 4 · n H 2 O occurs in exposed soils at the martian equator in summer where higher daytime temperatures at low relative humidity prevail against sluggish nighttime rehydration at high relative humidity. Desiccation and rehydration are both accelerated in the finest size fractions, particularly in silt-size aeolian particles subject to global redistribution by dust storms. This redistribution and periodic excursions into long-term episodes of high obliquity work to rehydrate desiccated MgSO 4 · n H 2 O to form epsomite, MgSO 4 ·7H 2 O, at higher latitudes in the first case and more globally in the latter. Kieserite, a monohydrate form of MgSO 4 · n H 2 O resistant to desiccation, can survive equatorial summer conditions, but not protracted high relative humidity; preservation of kieserite at the surface may place limits on the equatorial distribution of ice during past episodes of high obliquity. Deeper horizons in equatorial regolith may preserve hydrated phases through repeated obliquity episodes, raising the possibility of an ancient regolith archive of past hydration. At shallower depths in the regolith, in situ determination of the hydration states of the Mg-sulfates, and possibly the Ca-sulfates, may be used to constrain regolith dynamics if rates and modes of transitions in n can be fully characterized.

Membrane distillation crystallisation (MDC) can be used to recover crystalline products from solutions. MDC of a concentrated solution of magnesium sulphate of 375 g/l was investigated. It was found that the MDC of epsomite was achievable at a feed temperature of only 33 °C and a distillate temperature of approximately 17 °C. The orthorhombic crystals were formed at a growth rate of 1.6 × 10−8 m s−1. The transmembrane flux was then measured for the membrane distillation (MD) of two concentrated solutions of mixed electrolytes, MgSO4 and NaCl with concentrations of 225 and 225 g/l, respectively, for one mix; and 275 and 137.5 g/l, respectively, for the other mix. For the mixtures of salts, only sodium chloride was precipitated while magnesium sulphate remained in solution but increased in concentration. The geochemical equilibrium speciation program, PHRQPITZ, was used to determine solution activities. These results were verified by experimental vapour pressure values determined by dynamic vapour–liquid equilibrium (VLE) experiments to calculate the vapour pressures of the solution (and hence driving force) at each stage during the distillation. The accountability of water activities showed how the trend of decreasing flux fitted with that of the driving force for the distillation process. When operated in batch concentration mode the flux and driving force showed a constant initial rise (due to stabilisation of temperature and concentration profiles and fluid dynamics inside the module) after which it plateaus off before rapidly declining. Preliminary computer modelling has demonstrated how the understanding of membrane distillation processes can be improved by being able to predict driving forces.

Alpersite, Mg 0.58 Cu 0.37 Zn 0.02 Mn 0.02 Fe 0.01 SO 4 ·7H 2 O, a new mineral species with direct relevance to reactions in mine waste, occurs in a mineralogically zoned assemblage in sheltered areas at the abandoned Big Mike mine in central Nevada at a relative humidity of 65% and T = 4 °C. Blue alpersite, which is isostructural with melanterite (FeSO 4 ·7H 2 O), is overlain by a light blue to white layer dominated by pickeringite, alunogen, and epsomite. X-ray diffraction data (Mo K α radiation) from a single crystal of alpersite were refined in P 2 1 /c, resulting in w R = 0.05 and cell dimensions a = 14.166(4), b = 6.534(2), c = 10.838(3) A, β = 105.922(6)°, Z = 4. Site-occupancy refinement, constrained to be consistent with the compositional data, showed Mg to occupy the M1 site and Cu the M2 site. The octahedral distortion of M2 is consistent with 72% Cu occupancy when compared with the site-distortion data of substituted melanterite. Cuprian pentahydrite, with the formula (Mg 0.49 Cu 0.41 Mn 0.08 Zn 0.02 )SO 4 ·5H 2 O, was collected from an efflorescent rim on a depression that had held water in a large waste-rock area near Miami, Arizona. After dissolution of the efflorescence in de-ionized water, and evaporation of the supernatant liquid, alpersite precipitated and quickly dehydrated to cuprian pentahydrite. These observations are consistent with previous experimental studies of the system MgSO 4 -CuSO 4 -H 2 O. It is suspected that alpersite and cuprian pentahydrite are widespread in mine wastes that contain Cu-bearing sulfides, but in which solubilized Fe 2+ is not available for melanterite crystallization because of oxidation to Fe 3+ in surface waters of near-neutral pH. Alpersite has likely been overlooked in the past because of the close similarity of its physical properties to those of melanterite and chalcanthite. Alpersite is named after Charles N. Alpers, geochemist with the United States Geological Survey, who has made significant contributions to our understanding of the mineralogical controls of mine-water geochemistry.

Weathering of metal-sulfide minerals produces suites of variably soluble efflorescent sulfate salts at a number of localities in the eastern United States. The salts, which are present on mine wastes, tailings piles, and outcrops, include minerals that incorporate heavy metals in solid solution, primarily the highly soluble members of the melanterite, rozenite, epsomite, halotrichite, and copiapite groups. The minerals were identified by a combination of powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and electron-microprobe. Base-metal salts are rare at these localities, and Cu, Zn, and Co are commonly sequestered as solid solutions within Fe- and Fe–Al sulfate minerals. Salt dissolution affects the surfacewater chemistry at abandoned mines that exploited the massive sulfide deposits in the Vermont copper belt, the Mineral district of central Virginia, the Copper Basin (Ducktown) mining district of Tennessee, and where sulfide-bearing metamorphic rocks undisturbed by mining are exposed in Great Smoky Mountains National Park in North Carolina and Tennessee. Dissolution experiments on composite salt samples from three minesites and two outcrops of metamorphic rock showed that, in all cases, the pH of the leachates rapidly declined from 6.9 to b3.7, and specific conductance increased gradually over 24 h. Leachates analyzed after 24-h dissolution experiments indicated that all of the salts provided ready sources of dissolved Al (N30 mg L 1 ), Fe (N47 mg L 1 ), sulfate (N1000 mg L 1 ), and base metals (N1000 mg L 1 for minesites, and 2 mg L 1 for other sites). Geochemical modeling of surface waters, mine-waste leachates, and salt leachates using PHREEQC software predicted saturation in the observed ochre minerals, but significant concentration by evaporation would be needed to reach saturation in most of the sulfate salts. Periodic surface-water monitoring at Vermont minesites indicated peak annual metal loads during spring runoff. At the Virginia site, where no winter-long snowpack develops, metal loads were highest during summer months when salts were dissolved periodically by rainstorms following sustained evaporation during dry spells. Despite the relatively humid climate of the eastern United States, where precipitation typically exceeds evaporation, salts form intermittently in open

An integrated membrane system has been developed in order to recover dissolved salts that are present, at low concentration, in typical feed streams to desalination plants. The experimental work aimed to obtain CaCO3, NaCl and MgSO4·7H2O as solid products from nanofiltration retentate. Since gypsum scale causes reduction of SO42- content in the solution and drastically limits the recovery of epsomite, Ca2+ ions have been almost quantitatively precipitated by reaction with NaHCO3/Na2CO3. Sodium (bi)carbonate solutions have been produced by reactive absorption of CO2 into sodium hydroxide solutions carried out by membrane contactors technology. The flow sheet has been completed with a membrane crystallization stage that allows the generation of supersaturation for salts crystallization.

The study area is situated in the Askale sub-basin where the Early-Middle Miocene aged Askale Formation was deposited in a shallow marine to lagoonal environment, and consists of interstratifications of clastic sediments, carbonates and evaporites. The successions of the Askale Formation can be divided into four main members interfingering with one another both vertically and laterally, and composed of the sandstone-mudstone-limestone member, the evaporite member, the gravelstone-sandstone-mudstone intercalations and the limestone member. The evaporite unit comprises of secondary gypsum lithofacies formed by hydration of precursor anhydrite, anhydrite, gypsum-bearing limestone and claystone in the form of wedges and lenses. Massive, nodular, nodular-banded, laminated and laminated-banded gpysum lithofacieses in addition to chicken-wire and rare entrolithic structures were described, indicating a sabhka or a shallow water depositional environment. Alabastrine and porphyblastic textures of gypsum were identified within the all lithofacieses with abundant amount of anhydrite relics. Additionally, saponite and illite/smectite, calcite and dolomite, celestite, epsomite were also observed. Successions of the Askale Formation were deposited in stable subtropical climatic conditions within rapidly subsiding sub-basin resulted in conversion of sub-basin to shallow platform and even in lagoon environment. (C) 2015 Elsevier Ltd. All rights reserved.

The causes of the pathologies found on the lime renderings from Plaza de la Corredera facades are analysed in this study. For this purpose, the mineralogical and chemical analyses of the building materials -brickwork and rendering mortar- has been carried out, as well as their physical, hydric and mechanical properties have been determined. The obtained results from both unaltered and altered materials, and the analysis of the rendering's raw materials, have allowed us to establish that rendering deterioration is connected to the presence of saline compounds (gypsum, halite), which existing in the brickwork substratum, have been removed due to the water saturation of such brickwork. The main cause responsible of the alteration forms - efflorescence, crusts, grain-disintegration, bulging, flaking found on the renderings, has been the salts precipitation (halite, hexahydrite, epsomite) in their way towards the external surface.

Hot Lake (Oroville, WA) is an athalassohaline epsomite lake that can have precipitating concentrations of MgSO4salts, mainly epsomite. Little biotic study has been done on epsomite lakes and it was unclear whether microbes isolated from epsomite lakes and their margins would fall within recognized halotolerant genera, common soil genera or novel phyla. Our initial study cultivated and characterized epsotolerant bacteria from the lake and its margins. Approximately 100 aerobic heterotrophic microbial isolates were obtained by repetitive streak-plating in high-salt media including either 10% NaCl or 2 M MgSO4. The collected isolates were all bacteria, nearly evenly divided between Gram-positive and Gram-negative clades, the most abundant genera beingHalomonas, Idiomarina, Marinobacter, Marinococcus, Nesterenkonia, NocardiopsisandPlanococcus. Bacillus, Corynebacterium, Exiguobacterium, KocuriaandStaphylococcusalso were cultured. This initial study included culture-independent community analysis of direct DNA extracts of lake margin soil using PCR-based clone libraries and 16S rRNA gene phylogeny. Clones assigned to Gram-positive bacterial clades (70% of total clones) were dominated by sequences related to uncultured actinobacteria. There were abundantDeltaproteobacteriaclones related to bacterial sulphur metabolisms and clones ofLegionellaandCoxiella. These epsomite lake microbial communities seem to be divided between bacteria primarily associated with hyperhaline environments rich in NaCl and salinotolerant relatives of common soil organisms. Archaea appear to be in low abundance and none were isolated, despite near-saturated salinities. Growth of microbes at very high concentrations of magnesium and other sulphates has relevance to planetary protection and life-detection missions to Mars, where scant liquid water may form as deliquescent brines and appear as eutectic liquids.

Sebkha El Melah Natural Bnne is a complex high concentrated aqueous solution. To study this kind of saline solutions many authors assimilate them to a quinary system represented by Na', K', ~$1 Cl-, ~0~'- // H20 . In the case of Sebkha El Melah brine, magnesium and sulfate ions seems to be sufficiently high to recover Epsomite (MgS04.7H20). The aim of this work is firstly to apply the above mentioned diagram allowing the production of the considered sait, calculate the recovery rates and secondly to test the conceived process at the laboratoiy scale.