# Mineral Powder Extraction by the Natural Drying of Water from the Public Springs in Borsec
## 4 Discussion
The small amounts of sulfur detected by SEM-EDS for S3 and S11 precipitate towards the pseudo-dolomite prismatic crystals and do not form any detectable mineralization on their own. The successive intercalation of these crystals into the dendritic branches was evidenced by the SEM investigation coupled with the elemental map in Figure 6e. The rich abundance of Ca and Mg as the main mineralizers of the Borsec springs facilitates the fast formation of their specific crystals. The lesser sodium amount led to a weaker crystallization of the neutron particles following Equation (3), a fact proved by the few well-individualized natron crystals observed in the first stage by the POM images. The individualized natron crystals are also proved by the SEM image in Figure 7c. It is a possibility that the presence of already formed small calcite grains facilitates a partial heterogeneous crystallization for the natron crystals, a fact in accordance with the data in the literature reporting natron formation on porous building stones [30]. On the other hand, [PERSON] et al. shows natron precipitation using saline brine and CO\({}_{2}\)[31], a fact of great importance especially for spring 10 which has an increased salinity. The progressive accumulation of the well-individualized crystals ensures a relative organization of their relative positions to one another as observed in the POM images. It is a step forward to the final crystallization stage. The supersaturated solution loses its last water inducing a faster crystallization which forms a dendritic crust embedding the previously formed crystals (a fact confirmed by the MOM images of the last crystallization stage and the SEM microstructural details). In such a condition, the Cl\({}^{-}\) ions react with the remnant Na\({}^{+}\) ions forming halite crusts. This crystallization scenario is sustained by the POM observation of the halite deposits at the margins of the dendrites, a fact confirmed by the SEM elemental maps in Figure 7 and sustained by the halite crystallization modeling in the literature [32]. The amount of the formed crystals along with their precipitation mode is strongly dependent on the water's physicochemical properties, especially TDS and salinity. The relevant statistical group formed by S3, S5, and S11 leads to a weaker mineralization with smaller dendrites than those formed by the other relevant statistical group containing S6 and S10. On the other hand, both XRD and POM clearly show a greater level of mineralization for the samples collected in March 2024 compared to the samples from November 2023. The seasonality of the mineralization depends on the precipitation level, a fact reported in the literature for Borsec and its neighboring mineral waters [3; 33] and for other mineral waters all over the world [34; 35]. The water of these springs flows continuously, being available to those who want to drink or fill their bottle. Unused water flows into the nearby river. Its high mineral amount is not desirable for the freshwater river, influencing its ecological parameters. Such aspects could be improved if a small self-sustaining desalinization station is provided for each spring. The spilled water would obtain the desired parameters and the extracted mineral powder could be used for several applications. The crystallization process during water evaporation ensures an advanced mineral extraction from all investigated springs. Nevertheless, the higher mineralization found in S6 and S10 related to the constant flow of about 500 L/day is more favorable for mineral powder production than that of S3, S5, and S11. It will ensure a daily production of 0.75 kg/day for S6 and 1 kg/day based on the total dissolved solids (TDS) in Figure 2d. Such amounts might be produced by an integrated water evaporation system operated with solar cells ensuring a low carbon footprint. The vaporization facility might be placed nearby the spring location, playing a key role in the transformation of the mineral water into common river water which is better for the local environment.