Hydration processes of primary anhydrous minerals as well as dehydration of the hydrated phases are relevant not only for answering geochemical and petrological questions, but are also interesting in the context of the theory of the ‘Evolution of minerals’. Our study of the evolution of anhydrous exhalative sulfates in hydration and dehydration processes has demonstrated the complexity of the processes for a number of minerals from the active high-temperature fumaroles of Tolbachik volcano (chalcocyanite Cu(SO4), dolerophanite Cu2O(SO4), alumoklyuchevskite K3Cu3AlO2(SO4)4 and itelmenite Na2CuMg2(SO4)4). Hydration and dehydration experiments were carried out for all four minerals using powder X-ray diffraction. A typical structural characteristic of several anhydrous copper sulfate minerals of fumarolic origin is the presence of oxygen-centred OCu4 tetrahedra. These are absent in the structures of all known hydrated minerals or synthetic compounds of the class under consideration. Hydration of minerals initially containing O2– anions as part of oxocomplexes, proceeds with sequential formation of a large series of hydroxysalts. On the contrary, hydration of itelmenite with its relatively complex ‘initial’ structure, but without additional oxygen atoms that are strong Lewis bases, results in formation of simpler hydrates. The lower the temperature and the larger the excess of water, the stronger the tendency of the cations to adopt higher hydration numbers thus outcompeting the sulfate anions as ligands. Ultimately, the water molecules completely expel the bridging sulfate anions from the metal coordination sphere yielding relatively simple fully hydrated structures.

初级无水矿物的水合过程以及水合相的脱水不仅与回答地球化学和岩石学问题有关，而且在“矿物演化”理论的背景下也很有趣。我们对水合和脱水过程中无水呼出硫酸盐的演变的研究表明，Tolbachik火山的活性高温喷气孔（蓝晶石Cu（SO 4），白云石Cu 2 O（SO）4），铝矾土K 3 Cu 3 AlO 2（SO 4）4和钛铁矿Na 2 CuMg2（SO 4）4）。使用粉末X射线衍射对所有四种矿物进行水合和脱水实验。富马酸来源的几种无水硫酸铜矿物的典型结构特征是存在以氧为中心的OCu 4四面体。这些在所有已知的水合矿物质或所考虑类别的合成化合物的结构中均不存在。最初含有O 2–的矿物的水化阴离子作为含氧配合物的一部分，会依次形成一系列羟基盐。相反，具有相对复杂的“初始”结构但没有作为强路易斯碱的其他氧原子的依美石水合导致形成较简单的水合物。温度越低，水的剩余量越大，阳离子采用更高水合数的趋势就越强，因此胜过硫酸根阴离子作为配体。最终，水分子将桥连的硫酸根阴离子从金属配位球中完全排出，产生了相对简单的完全水合的结构。