This work presents a new discussion about the vibrational properties of the carbonate ion displayed in several different environments. The microparameters introduced by cation substitution and different crystal lattices in addition to the crystal aggregation are present in the discussion. The work comments on how the Raman modes are affected by these changes by using data obtained with four different laser excitation sources. Raman spectra excited at 1064 nm are reported at 1 cm⁻¹ resolution. New observations and approaches based on the Raman modes highlight the differences observed in the relative intensity and width of the bands. The new data contribute to the understanding of these materials and their spectra, bringing new observations based on the Raman modes. This work presents a new approach highlighting the differences observed in the relative intensity and width of the Raman bands. The results indicate some evidence of the influence of the crystal habit and/or the growth of the mineral itself on the Raman spectrum. In addition, the data show the influence of cation substitution upon Raman bandwidth and the interference of the size of the spot of the laser in the measurement.

This work presents a new discussion about the vibrational properties of the carbonate ion displayed in several different environments, not only the microparameters introduced by cation substitution and different crystal lattices but also the crystal aggregation, showing how their active Raman modes are affected by these changes by using data obtained with four different laser excitation sources. New Raman spectra excited at 1064 nm are reported for calcite, aragonite, and dolomite groups, also including magnesite, witherite, rhodochrosite, siderite, malachite and azurite. These new data contribute to the discussion and understanding of these materials and their spectra, bringing new observations based on the Raman modes, focusing on the internal symmetrical and asymmetrical stretching and bending modes of the carbonate ion, highlighting the differences observed in the relative intensity and width of the bands. The results indicate some evidence of the influence of the crystal habit and/or the growth of the mineral itself in the Raman spectrum. In addition, the data show the influence of the cation substitution upon the Raman band width and that small cations contribute to less rigid crystalline structures and, consequently, larger Raman bandwidths.

The structures of carbonate minerals, such as azurite and malachite, have been extensively studied, but some points are still unclear. This research uses Raman spectroscopy to analyze the vibrational characteristics of these minerals, focusing on the stretching modes of the carbonate anion. The results show an unexpected intensification of the asymmetric stretching mode compared to the symmetric one, suggesting a possible resonance Raman effect influenced by Albrecht's second term. Azurite exhibited a de‐enhancement of some vibrational modes, indicating an unusual antiresonance effect, probably due to Cu(II) ions and d–d electronic transitions. Electronic spectra revealed distinct electronic transitions, with maxima at 538 nm for malachite and 466 nm for azurite. The arrangement of copper centers may deform the carbonate anion, impacting both off‐resonance and resonance effects. This study provides insights into the vibrational properties of these minerals and suggests the need for further investigations.

This study investigates an unusual behavior observed in the Raman spectra of natural rhodochrosites under ambient conditions and varying temperature and pressure. While the typical MnCO₃ spectrum is maintained, the relative intensities of libration (L) and translation (T) bands exhibit significant variations, potentially linked to changes in the Mn²⁺ state within the crystal lattice. Mapping experiments under ambient conditions revealed intensity inversions in lattice modes depending on the sampling region and excitation wavelength. Initially attributed to laser-induced degradation, this phenomenon was ruled out by temperature-dependent Raman spectroscopy, which showed no significant intensity changes even under conditions promoting sample degradation. Further investigations under hydrostatic pressure revealed a decrease in L band intensity, potentially indicating crystal compaction and modified cation–anion interactions. Thermodynamic parameters were calculated using both linear and quadratic fitting methods, demonstrating that while linear fitting provides acceptable results for temperature-dependent analysis, a quadratic approach is crucial for pressure-induced changes, influencing the value of calculated Gruneisen and anharmonicity parameters. This work highlights the sensitivity of Raman spectroscopy to subtle changes within the rhodochrosite structure and provides valuable insights into the intricate interplay of temperature, pressure, and Mn ion configuration in this mineral.

This study investigates the production of acid-activated geopolymer mortars using phosphoric acid as the activator and metakaolin as the precursor, both individually and in combination with iron oxide. The optimum liquid-to-solid (L/S) ratio was determined for each formulation, considering a precursor-to-natural sand ratio of 1:3 by mass. Compressive strength, pH, ultrasonic pulse velocity, and chemical and microstructural characteristics were evaluated. In addition, a cradle-to-gate Life Cycle Assessment (LCA) was performed using SimaPro software and the EcoInvent database. A theoretical optimum L/S ratio of 0.24 was identified for metakaolin-based mortars and 0.32 for mortars containing metakaolin and iron oxide, considering a phosphoric acid solution with a molarity of 10 mol/L. Mortars containing iron oxide exhibited compressive strengths approximately twice those of mortars produced solely with metakaolin, reaching 28.8 MPa after 28 days. However, these mortars experienced a significant loss of strength over 90 days, whereas formulations containing only metakaolin showed a strength increase of up to 288.4% during the same period. Potential applications for this material include the production of non-load-bearing masonry blocks, structural masonry blocks, precast partition panels, and pedestrian pavements. Regarding the environmental impacts, the use of phosphoric acid as the activator was found to significantly increase the environmental footprint of the mortars, contributing 64.5 kg CO₂-eq per tonne of mortar produced with metakaolin alone and 83.3 kg CO₂-eq per tonne of mortar containing iron oxide, making it the primary contributor to the overall environmental impact of the system. Furthermore, the use of commercial iron oxide not only failed to improve the long-term mechanical performance but also further increased the overall environmental impact, indicating that the exclusive use of metakaolin as the precursor represents the more sustainable alternative.