## 3 Results and Discussion
(**a**) Micrographs: (**i**) SEM, (**ii**) optical image, (**iii**) Raman map (1086 cm\({}^{-1}\)); (**b**) Raman spectra; (**c**) FTIR spectra; and (**d**) PXRD. Bands on the biomorphs obtained under the conditions emulating the Precambrian atmosphere were identified via Raman spectroscopy at 158, 282, 713, and 1087 cm\({}^{-1}\) (Figure 3b, Table 1). The Raman signals identified in the biomorphs might correspond to the calcite (CaCO\({}_{3}\)) polymorph (Figures 2b,c and 3b,c). However, these calcium silico-carbonate biomorphs, having been synthesized on an igneous rock such as obsidian, made us wonder whether their synthesis under these conditions favored the interaction of the molecules dissolved in the aqueous solution with the obsidian molecules. If this were so, then the chemical composition of the biomorphs obtained might correspond mainly to CaCO\({}_{3}\) crystallites, in addition to the chemical elements that were taken from the obsidian. Should that be the case, there was a high possibility that we might be dealing with some polymorphs, such as parisite or rontgenite, considering the chemical composition of obsidian. The composition of the obsidian is important, as it has been shown in other contributions that when there is an interaction between a mineral and a solution, the chemical elements that make up both parts favor the synthesis of the new chemical molecule, as happens in a reaction mixture between solutions [18; 43; 44]. In order to answer this question, we must corroborate whether there was an interaction between the molecules in the solution with those of obsidian. The characterization of the FTIR spectra of the samples allowed us to observe the vibration bands that corresponded to the elements that made up the biomorphs. The biomorphs synthesized under the standard atmospheric conditions showed vibration bands at 712.5, 788.9, 873.6, 1057.4, 1412.3, and 2980.8 cm\({}^{-1}\) (Figure 2c, Table 1), while, in the case of the calcium silico-carbonates obtained under the conditions that emulated the Precambrian atmosphere, bands were observed at 783.0, 1035.2, 1450.0, and 2980.8 cm\({}^{-1}\) (Figure 3c, Table 1). Therefore, when observing the bands in the FTIR spectra, characteristic CO\({}_{3}\)\({}^{2-}\) bands can be identified, as the FTIR technique is especially sensitive to the detection and quantification of carbonates. \begin{table}
\begin{tabular}{l l l l l} \hline
**Ion** & **Sample** & **Type of Synthesis** & **Raman (cm\({}^{-1}\))** & **FTIR (cm\({}^{-1}\))** & **Composition/Reference** \\ \hline \multirow{4}{*}{Ca\({}^{2+}\)} & Control & Current & 160, 285, 714, 1087 & 712.1, 871.1, 1393.9 & calcite [40] \\ \cline{2-4}  & Precambrian & 162, 287, 717, 1089 & 713.1, 871.2, 1406.2 & calcite [40] \\ \cline{2-4}  & Obsidian & Current & 157, 282, 713, 1086 & 712.5, 788.9, 873.6, 1057.4, 1412.3, 2980.8 & rontgenite (DRX) [41] \\ \cline{2-4}  & Precambrian & 158, 282, 713, 1087 & 783.0, 1035.2, 1450.0, 2980.8 & rontgenite (DRX) [41] \\ \hline \multirow{4}{*}{Ba\({}^{2+}\)} & Current & 98, 141, 157, 226, 692, 1060 & 692.6, 768.5, 855.5, 1059.0, 1416.9 & witherite [42] \\ \cline{2-4}  & Precambrian & 96, 144, 162, 225, 694, 1063 & 692.4, 855.2, 1077.3, 1417.2 & witherite [42] \\ \cline{2-4}  & Current & 95, 138, 153, 691, 1059, 2907 & 783.5, 1023.3, 1425.1 & witherite [42] \\ \cline{2-4}  & Precambrian & 95, 138, 155, 224, 691, 1059 & 590.6, 692.9, 796.2, 856.0, 1058.7, 1432.3 & witherite [42] \\ \hline \end{tabular}
\end{table} 
Table 1: Identification through Raman and FTIR spectroscopies of the polymorphs of calcium or barium silica–carbonate biomorphs. Figure 3: Identification and characterization of the calcium silica–carbonate biomorphs synthesized on obsidian under conditions that emulated the Precambrian atmosphere. (**a**) Micrographs: (**i**) SEM, (**ii**) optical image, (**iii**) Raman map (1086 cm\({}^{-1}\)); (**b**) Raman spectra; (**c**) FTIR spectra; and (**d**) PXRD. The peak at 40\({}^{\circ}\) and 20 corresponds to the aluminum sample’s holder.