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Generation of Acid Mine Drainage
Published in Bruno Bussière, Marie Guittonny, Hard Rock Mine Reclamation, 2020
Benoît Plante, Gary Schudel, Mostafa Benzaazoua
Most sulfate minerals are hydrated and quite soluble. They will only be encountered in dry periods as efflorescent salts and will disappear upon re-wetting of the material (e.g., Nordstrom and Alpers 1999; Nordstrom 2011; Blowes et al. 2014). Typical examples of soluble hydrated sulfates comprise iron sulfate FeSO4.nH2O (1 < n < 7) and magnesium sulfates such as epsomite MgSO4.7H2O. Although jarosites are often composed of its K end-member (KFe3(SO4)2(OH)6; Equation 1.23), they will incorporate other cations as they are formed. More rarely, other end-member jarosites can also be encountered depending on the geochemical environment in which they are formed. Schwertmannite (Equation 1.24) may also be encountered in acid-generating tailings (Blowes et al. 2014) but is metastable and will transform to goethite (Schwertmann and Carlson 2005). However, some sulfate minerals are partly soluble, such as gypsum CaSO4·2H2O (Equation 1.25), or highly insoluble, such as barite BaSO4 (Equation 1.26), and may exert a significant control over the aqueous concentrations of their constituents. Gypsum is by far the most common secondary sulfate encountered in acid-generating mine wastes (Blowes et al. 2014) because of the prevalence of sulfate (from sulfide oxidation) and calcium (from carbonate and silicate dissolution) ions in mine waters.
Mineral Deposits
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
Gypsum, a mineral having the composition CaSO4 2H2O, is the most common sulfate mineral. It is often found as individual crystals, which, if clear, are called selenite. Photographs of some, especially large and beautiful gypsum crystals in Mexico’s Cuevo de los Cristales, are shown in Figure 4.1 of Chapter 4. These large crystals are some of the largest mineral crystals in the world.
Combination of immersion and semi-immersion tests to evaluate concretes manufactured with sulfate-resisting cements
Published in Journal of Sustainable Cement-Based Materials, 2019
E. Menéndez, R. García-Rovés, B. Aldea, S. Ruíz, V. Baroghel-Bouny
The sprayed concrete linings of Chinese railway tunnels located in Chuxiong city in the Yunnan Province were seriously damaged by sulfate attack. Secondary sulfate minerals such as gypsum formation under very high sulfate ion concentration condition by accumulating and evaporation process followed by crystallization of sulfate salt and formation of thaumasite were found. The deterioration of concrete was accelerated by factors such as poor quality of concrete, thin and in homogeneous shotcrete linings, and low strength and high permeability concrete. In addition, the low relative humidity caused by frequent running of trains speedups the transport process and even the crystallization from the aggressive salt solution of concrete [25].