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Empirical electronic polarizabilities allow the prediction of total mineral polarizabilities and mean refractive indices of the vast majority of minerals and synthetic oxides. However, deviations from the valence-sum rule at cations in some minerals are associated with large deviations of observed from calculated total polarizabilities. We have identified several groups of minerals and compounds where deviations from the valence-sum rule at cations lead to polarizability deviations of 2–5%: M(SO4)·nH2O, n = 1–6, blodite-group minerals [Na2M2+(SO4)2·4H2O], and the kieserite-related minerals: isokite, panasqueiraite and tilasite. In these minerals, the environment of the M ions contains both O and H2O: Mg[O4(H2O)2] in kieserite, szmikite, and szomolnokite; Mg[O2(H2O)4] in starkeyite, ilesite, and rozenite, and Mg[(H2O)6] in hexahydrite. In compounds where the ligands are only H2O, deviations from the valence-sum rule at the M(H2O)6 groups are not accompanied by significant polarizability deviations. This is the case for epsomite, MgSO4·7H2O; bieberite, CoSO4·7H2O; goslarite, ZnSO4·7H2O, six silicofluorides, MSiF6·6H2O; eighteen Tutton’s salts, M2M′(SO4)2·6H2O, where M = K, Rb, Cs and M′ = Mg, Mn, Fe, Co, Ni, Cu, and Zn; and eleven MM′(SO4)2·12H2O alums, where M = Na, K, Rb and Cs, and M′ = Al, Cr, Ga and In. This is also the case for the sulfates alunogen, Al2(SO4)3·17H2O and halotrichite, FeAl2(SO4)4·22H2O; three hydrated nitrates; one phosphate; three antimonates and two hydrated perchlorates. A possible explanation for this different behavior is that the bond-valence model treats O and H separately, whereas polarizability calculations treat the polarizability of the entire H2O molecule.

Solubilities, densities, refractive indices, and pH values for the ternary system (MgSO4 + Mg2B6O11 + H2O) at (288.15, 298.15, and 308.15) K and 0.1 MPa, obtained using the method of isothermal dissolution equilibrium, are reported for the first time. On the basis of the experimental data, the phase diagrams and the physicochemical properties of density, refractive index, and pH versus concentration of magnesium sulfate were plotted. It was found that there are one invariant point, two univariant curves, and two crystallization regions corresponding to inderite (Mg2B6O11·15H2O, Inde) and epsomite (MgSO4·7H2O, Eps). The crystallized area of inderite is larger than that of epsomite at three temperatures, indicating that the solubility of inderite is lower than that of epsomite. Comparison of the phase diagrams at (288.15, 298.15, and 308.15) K shows that the areas of Inde and Eps increase with increasing temperature. There are no solid solutions and double salts at these three temperatures in this system. T...

The Malanjkhand copper deposit, which is the largest open cast copper mine in Asia, is located in central India. The detailed hydrogeochemical study indicates that mine discharges are mostly highly acidic (pH 3.4–6.1) with very high concentration of Cu (9.2–60.8 mg/L). Water releases from the tailing pond is also acidic in nature (pH 2.39–2.48) and contains high concentration of Cu (15.6–65.2 mg/L). The water quality of the mine discharges and tailing is mainly affected by the oxidation of chalcopyrite, which presents abundantly in the host rock along with minor amount of pyrite. The blue coloured secondary mineral that precipitates along the course of the mine effluents is dominated by amorphous copper hydroxysulfate. Alpersite, gypsum, epsomite and hexahydrite occur as efflorescent salts during the summer time, and store very high concentration of metals. Alpersite contains Zn (285-391 mg/kg), Ni (62-78 mg/kg) and Cu (7.8-10.9%) whereas epsomite contains Zn (132-160 mg/kg), Ni (35-43 mg/kg) and Cu (3465-4184 mg/kg). Among the trace elements in tailing, Cu has the highest concentration ranges (98.2–4492 mg/kg) followed by Mn (131.4–760 mg/kg), Zn (54.3–241 mg/kg), Ni (25.7–170.3 mg/kg), Pb (12.5–46.4 mg/kg) and Cd (0.72–1.48 mg/kg). Tailing rich with efflorescent salt has maximum concentration of metals as well as maximum potential for releasing metals into the aqueous system.

We report on the geochemical interactions between a synthetic urban runoff (SUR) and the minerals of materials used in a multi-layered column filter (soil, sand, gravel, and tezontle) at the laboratory scale, which mimicked an unvegetated low-impact development (LID) system. After five 8 h infiltration cycles using the SUR, the average concentrations of Pb and Mn decreased slightly at the column outlet, as did HCO3−, SO42-, and Na+, whereas Mg increased and Cl−, Ca2+, and K+ were only detected at the outlet. The filter materials were comprised of silicates, Mn-bearing oxides (hausmannite and manganite), carbonates (calcite), chlorides (sylvite), and sulfates (anglesite, lanarkite, barite, and epsomite). PHREEQC modeling allowed the identification of the geochemical processes that occurred in the filter. The results showed the removal capacity of the filter materials through the formation of secondary minerals such as rhodochrosite (MnCO3) and the over-saturation of anglesite (PbSO4), and also showed that they may mobilize ions from the upper to the interior layers (as Mg2+ from epsomite, MgSO4·7H2O, and Ba2+ from barite, BaSO4). We highlight the importance of knowing the geological nature of filter materials used in LID systems because they may lead to the geogenic mobilization of toxic contaminants to the environment.

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.

This paper presents a thorough study of the main features and the decay causes and mechanisms of serpentinites both freshly quarried and after centuries exposure at the main facade of the sixteenth century Royal Chancery (Granada, Spain). In particular, the process of in situ formation of calcium and magnesium sulfates has been studied. Several decay factors are identified, all of them acting synergistically in the deterioration of slabs made of serpentinite. Among them, chemical weathering of sulfides such as pyrite present in the original serpentinite induces the formation of sulfate salts such as gypsum or epsomite, salts which are considered the main cause of decay. In addition, unsuitable restoration treatments involving the use of Portland cement to fill up cracks and surface lacunae, the polluted environment of the surrounding area, and the location of the slabs close to the ground, favoring capillary rise of water, all contributed to their deterioration. This work helps to gain knowledge on the deterioration process of ornaments made of serpentinite, allowing us to propose the most appropriate measures to guarantee their conservation.

On Mars, evidence indicates widespread calcium sulfate minerals. Gypsum (CaSO 4 ⋅2H 2 O) seems to be the dominant calcium sulfate mineral in the north polar region of Mars. On the other hand, anhydrite (CaSO 4 ) and bassanite (CaSO 4 ⋅0.5H 2 O) appear to be more common in large sedimentary deposits in the lower latitudes. The tropics are generally warmer and drier, and at least locally show evidence of acidic environments in the past. FREZCHEM is a thermodynamic modeling tool used for assessment of equilibrium involving high salinity solutions and salts, designed especially for low temperatures below 298 K (with one version adapted for temperatures up to 373 K), and we have used it to investigate many Earth, Mars, and other planetary science problems. Gypsum and anhydrite were included in earlier versions of FREZCHEM and our model Mars applications, but bassanite (the CaSO 4 hemihydrate) has not previously been included. The objectives of this work are to (1) add bassanite to the FREZCHEM model, (2) examine the environments in which thermodynamic equilibrium precipitation of calcium sulfate minerals would be favored on Mars, and (3) use FREZCHEM to model situations where metastable equilibrium might be favored and promote the formation or persistence of one of these phases over the others in violation of an idealized equilibrium state. We added a bassanite equation based on high temperatures (343–373 K). A Mars simulation was based on a previously published Na Ca Mg Cl SO 4 system over the temperature range of 273 to 373 K. With declining temperatures, the first solid phase under equilibrium precipitation is anhydrite at 373 K, then gypsum forms at 319 K (46 °C), and epsomite (MgSO 4 ⋅7H 2 O) at 277 K. This sequence could reflect, for example, the precipitation sequence in a saturated solution that is slowly cooled in a deep, warm aquifer. Because FREZCHEM is based on thermodynamic equilibrium, a crude approach to problems involving metastable equilibria is available by removing phases that may have kinetically inhibited formation. Removing anhydrite allows bassanite to precipitate at 373 K, followed by gypsum at 351 K (78 °C), and epsomite at 277 K. Removing anhydrite and gypsum allows bassanite to form from 373 to 273 K. But bassanite formation from warm to cold temperatures does not seem appropriate for Mars and Earth. An explanation for spatial patterns of gypsum, anhydrite, and bassanite on Mars and Earth could be past environmental differences. Anhydrite and bassanite are favored near Mars' equator with higher temperatures, along with drier, more saline, and more acidic environments. Gypsum would be favored at the lower temperatures in the Mars polar region with wetter, lower salinity, and less acidic environments. On Earth, Ca-sulfate would likely over time largely finish re-precipitating as the more insoluble gypsum. But Mars was not in long-term moderate climates compared to Earth that strongly influenced the dominance of gypsum on Earth. So while temperature and water/acid environments for CaSO 4 minerals on Mars may have been a major factor for these precipitations, the short-term moderate climates on Mars may also have influenced the prevalence of higher soluble CaSO 4 species in the lower Mars latitudes.

Salt mounds are commonly distributed along playa margins and typically comprise alternating layers of loose fine sand and slightly hard halite-rich sediments as a result of long-term underground spring activity. A model of salt mound development was constructed for this study. It suggests that wind-blown sand supply and upward recharge of underground springs are two important factors in salt mound construction. Furthermore, it proposes that salt mound height is mainly controlled by the vertical transport range of underground springs and the thickness of the capillary fringe. A 1.5 m representative profile dug from the center of salt mound LP1 in the Lop Nor playa revealed a fairly complicated mineral assemblage including halite, gypsum, anhydrite, glauberite, epsomite, anhydrite, calcite, bischofite, polyhalite, schoenite, kieserite and carnallite. This matches closely with the assemblage predicted by the EQL/EVP model. The groundwater in the area is highly concentrated brine rich in Cl − and Na + and poor in Ca 2+ , displaying low alkalinity, and containing considerable amounts of SO 4 2− , Mg 2+ and K + . Chemical analysis of groundwater revealed considerable variation in the salinity and chemical composition of groundwater over time. The Cs-137 technique was used to measure the accumulated ages of the salt mounds. This method may prove useful in the research of relatively young playa environments where carbon dating techniques are unworkable because of an absence of carbon-rich materials in recent saline sediments.

The Big Ledge mine located in northeastern Nevada, USA is a former barite mine site that now hosts an acidic pit lake and highly concentrated waste rock seepage, which flows into an intermittent stream. In an effort to identify the source(s) of the seepage, stable isotopic analyses were conducted (δ2H, δ18OH2O, δ18OSO4, and δ34S) in the pit lake, seepage, and groundwater. Additionally, inverse geochemical modeling was utilized to evaluate mixing relationships and mineral equilibria. Mass-balance calculations were also performed on the seepage/stream system to quantify discrete and diffuse solute inputs to surface waters. The stable isotopic composition of the pit lake and seepage display evaporative enrichment with the seeps being intermediate between the pit lake and groundwater, indicating that water in the seeps is partially sourced in the upgradient pit lake. Inverse modeling corroborates the isotopic mixing relationships, suggests that sulfide minerals could be dissolving along the flow path in the waste rock, and predicts the precipitation of sulfate salts from the concentrated seepage waters. Mineralogical analysis of efflorescent salts at the site, including epsomite (MgSO4·7H2O), pickeringite (MgAl2[SO4]4·22H2O), and melanterite (FeSO4·7H2O), corroborates the inverse modeling. Mass-balance calculations indicate the presence of diffuse acid mine drainage inflows along the creek, which, along with discrete inflows from waste rock seepage, contribute to sustained dissolved-metal transport in the perennial Tabor Creek downgradient from the mine.

Waste rock piles at the Macraes gold mine in southern New Zealand expose abundant fresh schist to alteration reactions that principally involve pyrite, chlorite, and calcite, yielding alkaline waters (pH~8) with elevated dissolved loads. Pyrite oxidation has resulted in dissolved sulfate concentrations rising up to ~3000 mg/L over 10 years, and this high sulfate is a potential environmental issue in waters leaving the site. Up to 600 mg/L dissolved Mg2+ results from chlorite dissolution. The site has a semi-arid climate and evaporative precipitation of sulfate minerals could contribute to an engineered water treatment system. However, the evolved waters are saturated or supersaturated with respect to carbonate minerals and spontaneous precipitation of aragonite is widespread, thereby limiting Ca-sulfate (gypsum) precipitation. Localised precipitation of Mg-sulfate (epsomite) also occurs, but this redissolves during rain events. Compositionally different waters seeping from the mine tailings impoundment have >2500 mg/L dissolved sulfate, and elevated Na+, K+ and Cl− from addition of reagents in the processing system. These seepage waters have also undergone interaction with waste rocks in the impoundment walls. The seep waters are approximately saturated with respect to carbonate minerals, but no spontaneous carbonate precipitation has occurred over two years of observations. Ephemeral evaporative epsomite and Na–Mg sulfate (bloedite) precipitates form locally. Geochemical modelling suggests that evaporative precipitation of gypsum has potential to remove sulfate from both types of water, especially if carbonate precipitation was suppressed by lowering the water pH to ~6 in an engineered treatment system that involves substantial evaporation.

The authors of the title paper (Materials Letters 223 (2018) 33–36) report to have newly synthesized trisglycine epsomite (TGE) single crystals by conventional solution growth method. In this comment, many points of criticism, concerning the crystal growth and experimental data of this so-called TGE crystal are discussed to prove that trisglycine epsomite is a dubious crystal.

This study investigates the use of an ultrasonic mister and hydrophobization with a silicone solvent barrier for the surface cleaning of water sensitive oil paints. Details are presented regarding the reconstruction of water sensitive paints through the growth of epsomite crystals on contemporary Winsor and Newton (W&N) oil paints via exposure to sulphuric gases, using samples that had been previously artificially aged and soiled. These samples were subsequently used for surface cleaning evaluations, specifically tailored to water sensitive oil paints. A number of aqueous solutions were tested with different application methods, including swabs and application with an ultrasonic mister in combinations with a brush and Evolon® tissue. Additionally, gels prepared with aqueous based solutions were tested with and without prior hydrophobization of the surface with silicone solvent cyclomethicone D5. The application of aqueous solutions with the mister were found to decisively reduce pigment removal from the water sensitive paints when compared to swab application. It was also found that the use of a cyclomethicone D5 solvent barrier reduces pigment removal during spreadable gel cleaning.

The study tailing pond shows a particular geometry resulting from the tailings stockpiles deposited onto the northern part of the beach. This generated three types of superficial waste: (i) tailings of the stockpiles (A-type) (pH=2.2-2.6; soluble fraction average - SF=14.2%), subjected to intense oxidation and evaporation; (ii) tailings of the lowlands of waste, characterized by low oxidation and no evaporation (B-type) (pH=2.7-3.1; SF=7.7%); (iii) salt crusts (C-type) (pH=2.6-3.5; SF=81.5%), formed by the evaporation of leachates accumulated in stagnant pools. Principal Component Analysis (PCA) showed the following sequences of secondary minerals precipitation: A-type waste (I - ferricopiapite, rozenite, ferrihydrite; II - jarosite, coquimbite); B-type (I - Fe oxyhydroxides; II - jarosite, butlerite); C-type (I - ferrihydrite, rozenite; II - alunogen, hexahydrite, epsomite). PCA also revealed that the abundance of Al (1-10% Al2O3 in A and B wastes; 1-5% in C waste) is particularly controlled by primary silicates and clay minerals. Iron (11-23% Fe2O3 in A and B wastes; 5-10% in C waste) is almost exclusively related to pyrite, ferrihydrite, and goethite. Moreover, Zn and Cd were collected by halotrichite, rozenite, jarosite, ferricopiapite, and apjohnite, whereas the clay minerals seem to trap selectively Cu, Pb and As in their structure.

The new minerals fermiite (IMA2014-068), Na4(UO2)(SO4)3·3H2O and oppenheimerite (IMA2014-073), Na2(UO2)(SO4)2·3H2O, were found in the Blue Lizard mine, San Juan County, Utah, USA, where they occur together as secondary alteration phases in association with blödite, bluelizardite, chalcanthite, epsomite, gypsum, hexahydrite, kröhnkite, manganoblödite, sideronatrite, tamarugite and wetherillite.Fermiite descriptive details: pale greenish-yellow prisms; transparent; vitreous lustre; bright greenishwhite fluorescence; white streak; hardness (Mohs) 2½; brittle; conchoidal fracture; no cleavage; slightly deliquescent; easily soluble in RT H2O; densitymeas = 3.23(2) g cm–3; densitycalc = 3.313 g cm–3. Optically, biaxial (+), α = 1.527(1), β = 1.534(1), γ = 1.567(1) (white light); 2Vmeas.= 51(1)°, 2Vcalc.= 50°; dispersionr 3σI) contains [(UO2)(SO4)3] chains that are linked by bonds involving five different Na–O polyhedra to form a framework. The mineral is named for Italian-American theoretical and experimental physicist Dr. Enrico Fermi (1901–1954).Oppenheimerite descriptive details: pale greenish-yellow prisms; transparent; vitreous lustre; bright greenish-white fluorescence; white streak; hardness (Mohs) 2½; slightly sectile; three good cleavages, {110}, {011} and {101}; irregular fracture; slightly deliquescent; easily soluble in RT H2O; densitycalc = 3.360 g cm–3. Optically, biaxial (+), α = 1.537(1), β = 1.555(1), γ = 1.594(1) (white light); 2Vmeas.= 72(2)°, 2Vcalc.= 70°; dispersion isr>v, moderate, inclined; optical orientation:X≈ ⊥ {101},Z≈ [111]; pleochroism: X very pale greenish yellow, Y pale greenish yellow, Z greenish yellow; X < Y < Z. EDS analyses yielded the empirical formula Na1.94(U0.97O2)(S1.02O4)2(H2O)3. Oppenheimerite is triclinic,P1,a= 7.9576(6),b= 8.1952(6),c= 9.8051(7) Å, α = 65.967(5), β = 70.281(5), γ = 84.516(6)°,V= 549.10(8) Å3andZ= 2. The structure (R1= 3.07% for 2337Io> 3σI) contains [(UO2)(SO4)2(H2O)] chains that are linked by bonds involving two different Na–O polyhedra to form a framework. The mineral is named for American theoretical physicist Dr. J. Robert Oppenheimer (1904–1967).

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.

The hydrocarbon generative potential of rocks was evaluated by modeling chemical interactions in the systems carbonate rock—seawater, silty sand rock—seawater, argillaceous rock—seawater, basalt—seawater, and granite—seawater at 25, 100, 200, and 300°C and over a pressure range from saturated vapor pressure to the platform thermal gradient. The term seawater is used here to describe the composition of marine solutions at the halite (SW2), epsomite (SW3), and sylvite (SW4) stages of evaporation. The hydrocarbon generative potential of rocks in these systems increases in the order clays > silty sands > carbonates > mafic rocks, while felsic rocks are nongenerative. It was shown that an increase in the rock—water mass ratio (R/W), which can be considered as a proxy for the duration (grade) of metamorphism, led to an increase in the reduction potential (logfH2) and hydrocarbon generative potential of rocks. At R/W → 1, logfH2 for carbonates, clays, and silty sands is equal to −2.74, −2.45, and −2.57 at 100°C; −1.2, −1.1, and −1.0 at 200°C; and −0.5, +0.3, and −1.2 at 300°C, which suggests that at higher temperatures (pressures) clays are more capable of reducing chemical elements in the water—rock system.

The WCL (Wet Chemistry Lab) instrument on board the Phoenix Lander identified the soluble ionic composition of the soil at the landing site. However, few studies have been conducted to understand the parent salts of these soluble ions. Here we studied the possible salt assemblages at the Phoenix landing site using two different thermodynamic models: FREZCHEM and Geochemist's Workbench (GWB). Two precipitation pathways were used: evaporation ( T > 0 °C using both FREZCHEM and GWB) and freezing ( T 0 °C using only FREZCHEM). Through applying three different models of initial ionic concentrations (from sulfate to chlorate/perchlorate dominated), we calculated the resulting precipitated minerals. The results—through both freezing and evaporation—showed some common minerals that precipitated regardless of the ionic initial concentration. These ubiquitous minerals are magnesium chlorate hexahydrate Mg(ClO3)2⋅6H2O, potassium perchlorate (KClO4) and gypsum (CaSO4⋅2H2O). Other minerals evidence specific precipitation pathway. Precipitation of highly hydrated salts such as meridianiite (MgSO4⋅11H2O) and MgCl2⋅12H2O indicate freezing pathway, while precipitation of the low hydrated salts (anhydrite, kieserite and epsomite) indicate evaporation. The present hydration states of the precipitated hydrated minerals probably reflect the ongoing thermal processing and recent seasonally varying humidity conditions at the landing site, but these hydration states might not reflect the original depositional conditions. The simulations also showed the absence of Ca-perchlorate in all models, mainly because of the formation of two main salts: KClO4 and gypsum which are major sinks for ClO−4 and Ca2+ respectively. Finally, in consideration to the Martian life, it might survive at the very low temperatures and low water activities of the liquids formed. However, besides the big and widely recognized challenges to life posed by those extreme environmental parameters (especially low water activity), another main challenge for any form of life in such an environment is to maintain contact with the small droplets of the stable liquids in the regolith and to interact with life in other isolated droplets.

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.

Perchlorates, in mixture with sulfates, chlorides, and carbonates, have been found in relatively high concentrations in martian soils. To determine probable soil salt assemblages from aqueous chemical data, equilibrium models have been developed to predict salt precipitation sequences during either freezing or evaporation of brines. However, these models have not been validated for multicomponent systems and some model predictions are clearly in error. In this study, we built a Pitzer model in the Na–K–Ca–Mg–Cl–SO 4 –ClO 4 –H 2 O system at 298.15 K using compilations of solubility data in ternary and quaternary perchlorate systems. The model is a significant improvement over FREZCHEM, particularly for Na–Mg–Cl–ClO 4 , Ca–Cl–ClO 4 , and Na–SO 4 –ClO 4 mixtures. We applied our model to the evaporation of a nominal Phoenix Lander Wet Chemistry Laboratory (WCL) solution at 298.15 K and compare our results to FREZCHEM. Both models predict the early precipitation of KClO 4 , hydromagnesite (3MgCO 3 ·Mg(OH) 2 ·3H 2 O), gypsum (CaSO 4 ·2H 2 O), and epsomite (MgSO 4 ·7H 2 O), followed by dehydration of epsomite and gypsum to kieserite (MgSO 4 ·H 2 O) and anhydrite (CaSO 4 ) respectively. At low residual water contents, our model predicts the precipitation of halite (NaCl), NaClO 4 ·H 2 O, and Mg(ClO 4 ) 2 ·6H 2 O, whereas halite and NaClO 4 ·H 2 O never precipitate in FREZCHEM. Our model predicts that calcite does not precipitate from evaporating WCL solutions at 298.15 K, which conflicts with other evidence for calcite in Phoenix soils. Previous studies that modeled freezing of WCL solutions found that calcite does form. Furthermore, our model predicts that ∼0.3 wt.% H 2 O is held in hydrated salts after the WCL solution has completely evaporated at 298.15 K, whereas previous studies have found that ∼1.3 wt.% H 2 O is held in hydrated salts if WCL solutions freeze. Given minimum water contents in Mars soils of 1.5–2 wt.% H 2 O measured from orbital spectra and in situ measurements, our modeling results suggest that salts at the Phoenix site were not formed during evaporation near 298.15 K, whereas formation during freezing remains possible.

High-resolution mapping by visible and near-infrared orbital spectrometers has revealed a diversity of hydrated mineral deposits on the surface of Mars. Quantitative analysis of mineral abundances within these deposits has the potential to distinguish depositional and diagenetic processes. Such analysis can also provide important constraints on the nature of putative global and local-scale mineralogical transitions on Mars. However, the ability of models to extract quantitative mineral abundances from spectra of mixtures relevant to sedimentary rocks remains largely untested. This is particularly true for clay and sulfate minerals, which often occur as fine-grained components of terrestrial sedimentary rocks and are known to occur in a number of sedimentary deposits on Mars. This study examines the spectral properties of a suite of mixtures containing the Mg-sulfate epsomite mixed with varying proportions of smectitic clay (saponite, nontronite, and montmorrilonite). The goal of this work is to test the ability of checkerboard (linear) and intimate (non-linear) mixing models to obtain accurate estimates of mineral abundances under ideal and controlled laboratory conditions. The results of this work suggest that: (1) spectra of clay–sulfate mixtures can be reproduced by checkerboard and intimate mixing models to within 2% absolute reflectance or single scattering albedo, (2) clay and epsomite abundance can be modeled to within 5 wt.% when particle diameter is optimized, and (3) the lower threshold for modeling clay in spectra of clay–epsomite mixtures is approximately 10 wt.%, below which the models often fail to recognize the presence of clay.

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.

In the western Sichuan Basin of China occurs an anticline in which high-K brines are found in the carbonate rocks of the Middle Triassic Leikoupo Group. The brine-bearing formation is at depth ranging from 4,465 to 4,565 m and the brines are enriched in a fault zone in the anticline. The PL4 well tapping the brine-bearing formation flows brines having TDS of 348.392–377.27 g/L, K contents of 48.95–53.267 g/L and B contents of 4.994 g/L. The TDS of the brines are close to those of the Yellow Sea water and the South China Sea water when evaporated to the stage of epsomite precipitation. The hydraulic head of the high-K brines in the PL4 well tapping the brine-bearing formation is calculated as high as 7,564 m and is 3,049 m above the land surface. A 3D numerical model is used to simulate the flow of the brines under the condition of exploitation and prediction calculation of the exploitation of the PL4 well is also performed. When the hydraulic head of the brines in the PL4 well is dropped to the land surface and to a depth of about 1,000 m below the land surface, the exploitable brine resources of the well are estimated as approximately 1.1 × 106 and 3.8 × 106 m3, respectively.

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.

The Coranda-Hondol ore deposit (Certej, Romania) is a sulfide ore deposit that was mined primarily for gold, silver, lead, and zinc. Secondary minerals were formed through a precipitation process from sulfate solutions with a high concentration of dissolved metals (especially Fe). These sulfate solutions resulted from acid mine drainage. Fourteen waste samples were analyzed through Raman spectrometry, X-ray diffraction, and scanning electron microscopy. Fe 3+ -, Fe 2+ -, Cu-, Zn-, Ca-, Mg-, and MnAl-hydrated sulfates were identified. All are unstable when exposed to the laser beam of the Raman spectrometer. Coquimbite, copiapite, ferricopiapite, hydroniumjarosite, and gunningite turn into anhydrous forms or oxides, depending on the laser power. Gypsum turns into bassanite, while apjohnite loses all water molecules at 53.6 mW laser power on the surface of the sample. Rhomboclase, melanterite, rozenite, antlerite, and brochantite break down without forming new minerals. Fe 2+ -sulfates do not change into hematite under laser irradiation. Epsomite and hexahydrite are stable at 53.6 mW laser power.

Alpersite, (Mg,Cu)SO4·7H2O, a metal hydrosulfate secondary mineral, is identified along a creek carrying copper plant effluent near Malanjkhand porphyry copper deposit, India. Alpersite occurs in the form of efflorescent salt and exhibits a typical blue color and prismatic habit. It is associated with other efflorescent salts consisting of epsomite, hexahydrite and gypsum. This paper reports the first occurrence of alpersite in India. Alpersite is found to precipitate from water at pH 6.2. Alpersite has shown high retention capacity of Mn, Zn and Ni; however, 92–98 % of total elements are found to be associated with the exchangeable part.

An isothermal dissolution method was employed to investigate the phase equilibrium at 308 K of the mixed aqueous system containing lithium, magnesium, sulfate, and borate. The solid phases of the invariant points were confirmed with the X-ray diffraction method. The stable phase diagram, the water content diagram, and the diagrams of the physicochemical properties versus the composition of the solution have been constructed. The system contained two invariant points (noted as E1 and E2), five univariant curves, and four crystallization fields corresponding to single salts epsomite (MgSO4·7H2O), hungchaoite (MgB4O7·9H2O), lithium sulfate monohydrate (Li2SO4·H2O), and lithium borate trihydrate (Li2B4O7·3H2O). Invariant points E1 and E2 are of commensurate invariant points. The crystallization fields decrease in the sequence MgB4O7·9H2O, Li2B4O7·3H2O, Li2SO4·H2O, and MgSO4·7H2O, which was contrary with the solubility of the salts. Compared with the temperature at 298 K, the crystallization area of salts MgB4...

This study reports two sets of dehydration experiments conducted on crystalline alunogen Al2(SO4)3·17H2O and melanterite FeSO4·7H2O under Mars relevant pressure (P) and partial H2O pressure (PH2O) at three temperatures (T). These experimental data are compared with those obtained from a similar set of experiments on crystalline epsomite MgSO4·7H2O, and revealed the differences in the phase transition pathways of the dehydrations of these hydrous sulfates, with different cations and the highest hydration degrees, under Mars relevant conditions. Specifically, the differences in the dehydration rates were discussed, and further compared with the dehydration processes of Ca-sulfate and Fe3+-sulfate of the highest hydration degrees. We found that the dehydrations of Mg-sulfate and Fe2+-sulfate would progress the fastest on Mars.

Water ice, hydrated salts, and other volatile ices such as carbon dioxide (CO2), have been detected by spectroscopy on Europa’s surface. Although the presence of other candidate compounds like clathrate hydrates have not yet been observed on the moon, the existence of water and carbon dioxide combined with low temperature and relatively high cryostatic pressure in the interior of the planetary body, favors their occurrence. In this study, the evolution of the H2O–MgSO4–CO2 system as a function of temperature, pressure and high salt concentration was investigated, focusing especially on the differences between the resulting mineral parageneses. CO2-clathrate formation and dissociation were examined by Raman spectroscopy in the presence of other hydrated phases crystallized from aqueous solutions rich in magnesium sulfate (MgSO4) at several concentrations (5, 17 and 30 wt%) from 268 to 290 K and pressures up to 60 bar. The CO2-clathrate experimental equilibrium line in this salty system is presented for both gas and liquid CO2 stability fields. During the heating process, the mineral assemblage of the system evolved differently depending on the salt concentration. At subsaturation (5 wt% of MgSO4), the CO2-clathrate co-existed with water ice from 268 to 272 K. However, when the initial sulfate concentration was 17 wt%, at a temperature above 269 K, no mineral phase was stable apart from CO2-clathrate. If the salt concentration of the system was supersaturated (30 wt%), CO2-clathrate co-existed with meriadianiite (MgSO4·11H2O) from 269 to 275 K. Subsequently, meridianiite was transformed into epsomite (MgSO4·7H2O) and continued crystallizing until 300 K. The evolution of the supersaturated solution at different heating rates was also evaluated in detail. In experiments with the fastest heating, the epsomite was not stabilized and the resulting aqueous solution became more concentrated than initially, promoting a clathrate dissociation at lower temperatures than expected. Volume changes due to mineral transformations and partial/total melting processes were assessed for the system and applied to Europa’s geology. Thus, assuming that this system is present in Europa’s interior, the evolution of the presumed fluids and mineral assemblages may have resulted in the generation of local stresses promoting resurfacing. Depending on the initial composition of the system, the percentage of volume change would imply a chaotic terrain formation, or cause faulting.

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.

Mining wastes of Zn–Pb ores were studied at Olkusz, Southern Poland, using X-ray diffraction, SEM/EDS analyses. Additionally the chemistry of surface water runoff collected on the tailings slope was analyzed. The surface layer of tailing piles contains pyrite and marcasite, and dolomite as predominant carbonate mineral. The principal secondary sulfate mineral is gypsum, but the presence of trace epsomite was also inferred. Grains of dolomite are relatively fresh: the source of Ca necessary for crystallization of gypsum seems to be highly corroded minor calcite. In surface runoff, pH is close to neutral; Ca and sulfate are the dominant ions, followed by Mg. Concentrations of sulfate reaches 939 mg/l, whereas concentrations of Ca and Mg are 389 mg/l and 15.43 mg/l, respectively. The principal heavy metal in runoff is Zn, reaching 2.65 mg/l. Most species in runoff exhibited a negative correlation with the amount of precipitation in 5 days preceding the formation of surface runoff, due to their presence in efflorescent salts precipitated in dry period. Bicarbonate showed a positive correlation with the amount of precipitation, probably due to enhanced dissolution of calcite under high water saturation conditions. The results of this study indicate a dominant role of the surface layer of tailings and previous precipitation conditions in the formation of the surface runoff chemistry. In the future, surface runoff and fast releases of contaminants may become more important as a consequence of on-going climatic changes resulting in higher intensity of storm events.

At low temperature ( T ), sulfates with high degree of hydration (epsomite and ferricopiapite) have the enlarged stability fields toward low relative humidity ( RH ). They are capable of maintaining high RH in a closed environment and keeping an aqueous film at their grain surfaces. More importantly, their dehydration processes are much slower than H 2 O ice sublimation. Using the activation energy ( Ea ) of epsomite dehydration, derived experimentally at Mars relevant atmospheric pressure ( P ) and partial pressure of H 2 O ( P H2O ), we estimated the half-life ( t 1/2 ) of epsomite dehydration within a model predicted T range of subsurface sulfate-rich layer at Mars equator. We found that subsurface hydrous sulfates formed during past high obliquity periods (>45°) have a high probability to maintain mid-to-high degrees of hydration even until the present epoch. This prediction based on experiments is consistent with an observation made by the Spirit rover at Gusev on Mars, and with a field observation at a hyperarid site on Tibet Plateau. Our study supports the hypothesis that subsurface hydrated sulfates are the major host for the high water-equivalent-hydrogen (WEH) values observed at two equatorial regions on Mars.

The coal (anthracite A) in Douro Coalfield (NW of Portugal) has been exploited for many years and has been mainly used as fuel supply by a thermal power plant. The mining activities inevitably impacted the environment, which includes a large number of coal waste piles emplaced over the old mine sites and adjacent areas of the Douro Coalfield. The disposal of coal mining residues represents significant environmental concerns due to their potential influence on soils and sediments, as well as on the surface and groundwater of the surrounding areas. In the present study, the development of sequential extraction combined with various advanced analytical techniques was performed to provide an improved understanding of the complex processes related with sulfide-rich coal waste oxidation, sequences of mineral formation, and the transport mechanisms of hazardous elements by specific neoformed soluble minerals. The results showed the presence of amorphous iron (oxy-) hydroxides and goethite with various degrees of crystallinity, containing hazardous elements, such as As, Cr, Hg, Mo, Se, Pb, U, and others. Some of the neoformed minerals found in the coal waste material are the same as those commonly associated with coal acid drainage, in which oxidation of sulfides plays an important role. The precipitated neoformed minerals include pickeringite, blodite, and a mixture of epsomite, pickeringite, and hexahydrite. As these sulfates may dissolve after the first rain, they may release above-mentioned elements into surrounding water bodies.

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.

Wilcoxite, (Mg 0.81 Mn 0.07 Fe 0.04 Zn 0.04 )∑ 0.96 Al 1.01 (SO 4 ) 2 F 1.02 •17H 2 O, is a secondary sulfate mineral that occurs in hydrothermal systems containing significant amounts of fluorine. A sample of wilcoxite was collected from abandoned mine workings east of Rico, Dolores Co., Colorado, U.S.A., where it occurs as white, efflorescent crusts composed of small anhedral crystals within a timber crib that protected the material from direct exposure to rain and snow, but not from changes in the humidity and temperature of the atmosphere. It is remarkable that this highly hydrated mineral has remained stable under these conditions. Unit cell dimensions are a 6.644(1), b 6.749(2), and c 14.892(3) A, α 79.664(4)°, β 80.113(4)°, γ 62487(3)°, and V 579.6(2) A 3 , space group P The previously unknown crystal structure was determined from single-crystal X-ray diffraction data and consists of isolated sulfate tetrahedra, Mg(H 2 O) 6 octahedra, and Al(H 2 O,F) 6 octahedra connected only through hydrogen bonding involving additional water molecules. Wilcoxite has 1.5 water molecules per sulfate tetrahedron that do not participate in the formation of an Al(H 2 O,F) 6 or Mg(H 2 O) 6 octahedron. The water molecules held within the epsomite (MgSO 4 •7H 2 O) structure are lost if the relative humidity (RH) drops below 50% at 298 K, and hexahydrite (MgSO 4 •6H 2 O) loses water to form starkeyite (MgSO 4 •4H 2 O) at 40% RH at 298 K. The fact that wilcoxite, with such a high water content, is stable when the magnesium sulfate with which it coexists has become starkeyite indicates that water molecules are more tightly bonded within the wilcoxite structure. If epsomite crystals are warmed slightly they slowly become first translucent and then an opaque white powder, whereas wilcoxite does not dehydrate but abruptly melts when warmed. This behavior is similar to the incongruent melting of meridianiite (MgSO 4 •11H 2 O) on warming above 2 °C.

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

Evaporites are mineral facies frequently occurring in salt marsh environments in arid climates. Considering that groundwater and soil salinity play an important role in the development of salt marsh ecosystems, the aims of this work are to study the occurrence and precipitation/dissolution processes of evaporites of marine origin and to evaluate how such processes influence groundwater chemistry in the Fracasso Beach salt marsh (Península Valdés, Argentina). Groundwater and seawater samples were collected for isotopic and chemical analysis. Ionic speciation and saturation indices were estimated, and the modelling of theoretical seawater evaporation was undertaken. The estimation of the isotopic variations due to evaporation was carried out according to an analytical model. To study the evaporites, soil salt crust samples were collected in the different sectors of the marsh and then observed in a scanning electron microscope with an X-ray energy-scattering micro-analyzer. The evaporite minerals occurring in different areas of the salt marsh show that there are changes in the dominance and type of evaporites depending on the topographic height. In the most elevated areas, abundant halite and gypsum/anhydrite precipitates are registered, accompanied by epsomite and bischofite, whereas in the lower salt marsh, mainly halite can be observed and, to a lesser extent, gypsum and scarce epsomite. The dissolution of all the evaporites is verified in the groundwater chemistry; the results show that the process of precipitation/dissolution of marine evaporites is the main determinant of groundwater salinity in the Fracasso Beach salt marsh. The variation in ion content registered within the salt marsh is related to the recurrence of the tidal flooding in each sector, as it renews the groundwater. This indicates that in the highest sectors the evaporation percentages are higher, and it confirms that the occurrence of evaporite minerals is determined by their closeness to the sea, the topographic height and, therefore, by the flooding frequency. Fil: Alvarez, Maria del Pilar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico para el Estudio de los Ecosistemas Continentales; Argentina Fil: Carol, Eleonora Silvina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; Argentina Fil: Bouza, Pablo Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico para el Estudio de los Ecosistemas Continentales; Argentina

Acid mine waters (AMW) collected during high- and low-flow water conditions from the Lousal, Aljustrel, and Sao Domingos mining areas (Iberian Pyrite Belt) were physicochemically analyzed. Speciation calculation using PHREEQC code confirms the predominance of Men+ and Me–SO4 species in AMW samples. Higher concentration of sulfate species (Me–SO4) than free ion species (Men+, i.e., Al, Fe, and Pb) were found, whereas opposite behavior is verified for Mg, Cu, and Zn. A high mobility of Zn than Cu and Pb was identified. The sulfate species distribution shows that Fe3+–SO4 2−, SO4 2−, HSO4 −, Al–SO4, MgSO4 0, and CaSO4 0 are the dominant species, in agreement with the simple and mixed metal sulfates and oxy-hydroxysulphates precipitated from AMW. The saturation indices (SI) of melanterite and epsomite show a positive correlation with Cu and Zn concentrations in AMW, which are frequently retained in simple metal sulfates. Lead is well correlated with jarosite and alunite (at least in very acid conditions) than with simple metal sulfates. The Pb for K substitution in jarosite occurs as increasing Pb concentration in solution. Lead mobility is also controlled by anglesite precipitation (a fairly insoluble sulfate), where a positive correlation was ascertained when the SI approaches equilibrium. The zeta potential of AMW decreased as pH increased due to colloidal particles aggregation, where water species change from SO4 2− to OH− species during acid to alkaline conditions, respectively. The AMW samples were supersaturated in schwertmannite and goethite, confirmed by the Men+–SO4, Men+–Fe–O–OH, or Men+–S–O–Fe–O complexes identified by attenuated total reflectance infrared spectroscopy (ATR-IR). The ATR-IR spectrum of an AMW sample with pH 3.5 (sample L1) shows well-defined vibration plans attributed to SO4 tetrahedron bonded with Fe-(oxy)hydroxides and the Men+ sorbed by either SO4 or Fe-(oxy)hydroxides. For samples with lower pH values (pH ~ 2.5—samples SD1 and SD4), the vibration plans attributed to Men+ sorption are not evidenced, indicating its release in solution. The sorption of heavy metals on the first precipitated simple metal sulfates was ascertained by scanning electron microscopy coupled with X-ray spectrometry (SEM-EDX), where X-ray maps of Cu and Zn confirm a distribution of both metals in the melanterite structure.