## 4 Results and Discussion
### Malachite  
Malachite is a copper carbonate hydroxide (Cu\({}_{2}\)CO\({}_{3}\)(OH)\({}_{2}\)) occurring as a secondary mineral in the oxidized zones of copper ore deposits. The essential features of the malachite structure are based on Cu\({}_{2}\)O\({}_{6}\) dimers bonded to CO\({}_{3}\) groups [47]. Its name comes from the Greek \"malache\", which means \"mallow\", an herb with green leaves. Since antiquity, malachite was used as a green pigment and as an ornamental stone as well as a primary source of copper [35; 41; 42]. Malachite deposits are found in Africa, Russia, Australia, and United States. The malachite identified in the Masticarro Barite Mine is a chalcopyrite alteration product with an intense green color and vitreous-silky luster that often occurs on irregular pale white aggregates of cerussite crystals (Figure 14a). It forms dome-shaped aggregates of needle-like crystals up to 0.5 mm in size. A double-rosette aggregate morphology was also observed (Figure 14b). This morphology is very similar to that found in Morocco and at the Tsunpe M Mine in Namibia.  
Figure 11: Optical image showing light blue monoclinic langite crystals from the Masticarro Barite Mine (Catanzaro, southern Italy) arranged in a radial pattern.  
Figure 12: SEM image and corresponding EDS spot analysis (red filled square) of monoclinic langetic crystals from the Masticarro Barite Mine (Catanzaro, southern Italy).  
A qualitative EDS/SEM analysis of single crystals (Figure 15) revealed that the chemical composition of malachite is generally close to the ideal one, with 74.7 wt% CuO and 23.9 wt% CO\({}_{2}\). Samples also contain minor impurities of Si, Mg, and Ca at the surface of the crystals as EDS detected (Figure 15). Malachite often grows on pseudo-circular holes and exhibits a lamellar habit (Figure 15).  
Figure 14: Optical images showing malachite crystals from the Masticarro Barite Mine (Catanzaro, southern Italy): (**a**) white acicular tufts of cerussite and dome-shaped aggregates of green needle-like malachite crystals; (**b**) double rosette aggregate of green needle-like malachite crystals.  
Figure 13: Raman spectrum of langite crystals from the Masticarro Barite Mine (Catanzaro, southern Italy). In the insert is the structure of the langite [40; 46].  
The Raman spectrum of malachite contains modes of three separate vibrational groups: OH, CO\({}_{3}\), and Cu-O [43]. In Figure 16 are visible the typical malachite bands at 1493, 1366, 1099, 1064, 718, 536, 510, 434, 353, 275, 221, 180, and 154 cm\({}^{-1}\) (Table 1), in agreement with spectra reported in the literature [28; 35; 39; 43]. In particular, the CO\({}_{3}\) symmetric stretching mode (\(v_{1}\)) is observed at 1099 and 1064 cm\({}^{-1}\), the \(v_{3}\) mode at 1493 cm\({}^{-1}\), and the \(v_{4}\) mode at 718 cm\({}^{-1}\); the OH stretching modes are visible at 536, 434, 275, and 221 cm\({}^{-1}\), while for the Cu ion, there is a band at 353 cm\({}^{-1}\). Moreover, in this case, new Raman bands at 120, 111, 79, and 65 cm\({}^{-1}\) (Table 1), that have not been previously described in the literature, were highlighted.  
Figure 16: Raman spectrum of malachite crystals from the Masticarro Barite Mine (Catanzaro, southern Italy). In the insert is the structure of the malachite [47].  
Figure 15: SEM image and corresponding EDS spot analysis (red filled square) of malachite crystals from the Masticarro Barite Mine (Catanzaro, southern Italy).