Figure shows that talc is a stable mineral against acid, which is why leaching is not complete even after 24 h, in contrast to calcium extraction. Figure (right) also shows the low yield of magnesium at 3 % of the amount used. With such a small amount, it is likely that it is not the dissolved talc, but the trace elements of the organic components. In the two tailings, no explicit minerals can be assigned to the magnesium content, making a prediction difficult. However, it is noticeable that the leaching is not complete after 24 h and that the decreasing trend is similar to that of talc and anhydrite. A similar proportion of the magnesium present is leached from both tailings with 𝐶 𝑀𝑔,𝑖 * = 0.17. Since the iron tailings contain 1.5 times the amount of Mg 2+ according to Table , this means that the proportion has no effect on the chemical equlibirum.