# Mineral Powder Extraction by the Natural Drying of Water from the Public Springs in Borsec
## Results
### Mineral Crystallization Assessment
The crystalline powder formed after the glass slide scratching reveals finer particles embedded in the crystalline crust of the broken dendrites, as shown in Figure 4(b3). Spring 6 has a high mineralization that induces the precipitation of a lot of germination centers due to the reaction of the alkaline ions with carbonic acid. These crystals progressively grow as individual well-formed particles during the first stage, shown in Figure 4(c1). The most obvious and representative crystals are calcite (including pseudo-hexagonal and rhombic forms) and prismatic crystals of pseudo-dolomite. The fast increasing of the concentration gradient during the final stage of the drying process induces a rapid crystallization of the remnant liquid, and large dendritic flowers are formed having a span of 50-200 \(\upmu\)m, shown in Figure 4(c2). The dendritic structure is formed on the calcite crystals formed in the first phase and embeds the other free crystals in their close vicinity. The dense mineralization is also observed in the broken dendrites' microstructure in Figure 4(c3). The pale white aspect of the embedding material is induced by the mean overlapping of the light specific to calcite, pseudo-dolomite, and halite. The embedded individual crystals appear as bright spots shining in their specific color range. Spring 10 has the most intense mineralization compared to the other investigated springs. This leads to a fast development of many crystallization centers as a consequence of Ca\({}^{2+}\), Mg\({}^{2+}\), and Na\({}^{+}\) ions with carbonic acid generating the fast development of calcite, pseudo-dolomite, and aragonite fine crystals, shown in Figure 4(d1). Calcite and pseudo-dolomite crystals (having yellow-brown color) are slightly bigger than aragonite, which appear as small blue-violet spots. The natron crystals are very small and thin with acicular yellow appearance being easily overlooked beside bigger calcite crystals, but some of them are more visible on the left median side of Figure 4(d1). The final stage of crystallization involves the supersaturated solution and subsequent concentration gradient that facilitate dendrite formation. The abundance of growing centers causes the increasing of the number of dendrite flowers and the relative reducing of their size of about 30-100 \(\upmu\)m as observed in Figure 4(d2). Similar dendrite is observed in Figure 5(d2). The dendrite's borders have a pale blue aspect caused by the significant presence of halite platelets crystallized in the cubic system typically oriented on the (200) crystallographic plane, in agreement with the XRD observation and literature data [22]. The scratched powder reveals the aspect of the broken dendrites; see Figure 4(d3). Spring 11 is less mineralized compared to the other investigated springs. This fact is sustained by the relatively weaker diffraction peaks observed in Figure 3a. Therefore, the initial crystallization stage occurs with only several germination centers allowing for the progressive growth of relatively bigger crystals, as shown in Figure 4(e1). Most of them belong to the calcite sustaining the XRD observation, and only a few pseudo-dolomite and aragonite crystals are observed. Natron and halite crystals are not observed in the initial stage. The progressive drying induces a concentration gradient that finally results in the supersaturated solution that allows for the dense precipitation of the remnant minerals due to the reaction of the alkaline ions with the carbonic acid. It consolidates some dendritic chains containing previously formed individual crystals embedded in a crystalline crust having pale blue color; see Figure 4(e2). Figure 4(e3) shows the scarce mineral content compared to the other investigated springs' samples. The POM results for all investigated samples from the first campaign are centralized in Table 3 along with the XRD results.