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Basis and methods for in-situ measurements on liberation and generation of volatile components concerning the disposal of high-level radioactive waste in rock salt
Published in B. Côme, P. Johnston, A. Müller, Design and Instrumentation of In Situ Experiments in Underground Laboratories for Radioactive Waste Disposal, 2022
Rock salt from the North German salt domes which is foreseen for the disposal of high level radioactive wastes consists, besides the main mineral halite, of the minor minerals polyhalite, anhydrite and kieserite in the range from 0,1 to 5 wt %. In some small layers the concentration of the minor minerals reaches up to 30 wt %. As a result of the hydrated minerals rock salt contains small amounts of water. 55 % of the investigated samples have a water content of less than 0,1 wt % and 75 % less than 0,2 wt %. The amount of water adsorbed on the crystal boundaries and in fluid inclusions is rather low as compared to the water derived from the hydrated minerals. Besides the minor minerals and water, rock salt contains traces of further solid components, such as clay, bitumen and carbonates as well as gases, such as CO2, H2S, CH4 and further hydrocarbons. These gases will be liberated into the ventilation air or into the sealed disposal boreholes at natural mine temperatures already. Further heating and γ-radiation of the rock salt will lead to liberation and generation of further gas components, such as H2; O2; O3; HC1; Cl2; SO2; H2O as a result of thermal cracking and radiolysis. The amount of these components depends on the mineralogical composition and the stratigraphic layer of the rock salt.
Exploration and categorization of evaporite deposits
Published in M.L. Jeremic, Rock Mechanics in Salt Mining, 2020
Potash is composed of the various potassium minerals sylvinite, carnallite, polyhalite, and magnesium, sodium, calcium and other saline minerals as well (Figure 6.4.6). The characterization of the potash ore mostly depends on its particular mineral associations and the quantity of individual minerals present. For example, potash from Saskatchewan occurs in beds and the dominant mineral is carnallite which lowers its strength significantly. For example, the presence of about 10% of carnallite decreases the compressive strength of potash ore up to 50%.
Sediments and Sedimentary Rocks
Published in Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough, Earth Materials, 2019
Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough
Waters of both the Mediterranean Sea and the Gulf of Mexico have deposited thick layers of evaporite minerals in the past when they became isolated from the larger oceans and evaporation led to oversaturation. In both places, when ocean water evaporated, precipitation started with minerals that were least soluble in water and progressed to those that were most soluble. So, initial precipitates were calcite (CaCO3) and other carbonates. Subsequently, gypsum (a sulfate) and halite (a chloride) were deposited—and then more sulfates and chlorides, including anhydrite, sylvite, carnallite, langbeinite, polyhalite, and kainite. Massive layers of all these minerals underlie both the Mediterranean and the Gulf of Mexico today.
The use of seawater in mining
Published in Mineral Processing and Extractive Metallurgy Review, 2018
Luis A. Cisternas, Edelmira D. Gálvez
The natural deposits of nitrates or saltpeter are called caliche (Wisniak and Garces, 2001). This mineral is a conglomerate of various mineralogical species that in a high proportion are soluble in water at room temperature, being the most abundant: polyhalite, glauberite, bloedite, gypsum, and anhydrite (sulfates), halite (chloride) and nitratine, humberstonite and darapskita (nitrates). On the other hand, there are lautarita and hectorfloresite (iodates) and some chromates and perchlorates, which are in small proportions. The insoluble species (approximately 60% to 70%) that the caliche also contains are mainly quartz and other silicates (Valencia et al., 2008). The Caliche exploitation is concentrated in Northern Chile, in the Atacama Desert, and produces mainly natural sodium nitrate (a fraction then is converted into potassium nitrate) and iodine (approximately 22,000 t/year).
Pyroclastic Stones as Building Materials in Medieval Romanesque Architecture of Sardinia (Italy): Chemical-Physical Features of Rocks and Associated Alterations
Published in International Journal of Architectural Heritage, 2022
Stefano Columbu, M. Palomba, F. Sitzia, G. Carcangiu, P. Meloni
Also, K-Ca-Mg sulphates, like gypsum and polyhalite, which mainly occur in patinas, exfoliations, and crusts, were occasionally detected in different amounts. Gypsum is the most abundant sulphate phase detected, originating from sulphation phenomena, which favor and allow the recombination of calcium, contained in the feldspars and in volcanic glass, with sulphur carried by the acid rains. The gypsum, in the samples of San Nicola Church, occurs from traces to minor occurrence. Polyhalite (K2Ca2 Mg(SO4)4 · 2H2O), a sulphate salt, was detected as efflorescence in one sample the of San Nicola Church, in amounts not exceeding 5 wt%. SEM studies, besides to confirm the presence of primary and newly formed minerals well evidenced by XRPD technique, highlight the occurrence of other primary accessory minerals, undetectable by diffractometry, because of the content in the sample are below the detection limit. Augite, Ti-magnetite, ilmenite, and biotite crystals are quite common species, and generally occur inside the glassy matrix. Among the newly formed minerals, only detectable by SEM studies, Zeolite-Group minerals locally occur in minor proportion. They generally occur as products of devitrification of the pumices and/or web-like fibres formed at the expenses of the volcanic glass. SEM studies also evidence structural and textural aspects of the rocks. The typical anisotropy is highlighted by the fluidal-like texture due to the orientation along a preferential direction of glass shards, crystals, pumices, and lithic fragments. The presence of microstructural discontinuities, and open/closed micropores, also characterizes the study lithofacies. Micro-fractures are generally filled by newly formed mineral species like zeolites.