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Ojo de la Reina is the first and the smallest cave intersected at the -290 level in the Naica Mine (Mexico), therefore it was the first cavity in which the lowering of temperature induced by mine ventilation caused condensation over crystals’ surface since 2005. The consequent dissolution of the gypsum crystals and subsequent condensed water evaporation lead to the deposition of several new minerals, among which some highly soluble Mg/Na compounds (bloedite, epsomite, halite, hexahydrite, kieserite, starkeyite). The single available source of Mg and Na ions in this minerogenetic environment is represented by the huge fluid inclusions widespread within the crystals. The condensation occurs mainly along the widened principal exfoliation (010) planes, and allows to an easy and fast opening of the fluid inclusions that consequently drip Mg-rich fluids stored inside them. Finally the evaporation of the relatively small volumes of involved water allows to the development of the high soluble Mg and Na compounds.