Spectroscopic characterization of rare hydrated ammonium borate mineral larderellite

Two samples of larderellite (NH4)B5O7(OH)2·H2O from Monte Rotonda (Italy) have been studied. Spectroscopic methods, like infrared and Raman spectroscopy, were used in combination with thermal analysis and X-ray diffraction. The main objective was vibrational characteristic of research mineral and, based on the obtained results, test how the long storage of minerals affect their structure. Raman and infrared spectroscopy confirm the presence of tetrahedral and trigonal boron structural units in the investigated samples. The most intensive Raman band is located at 149 cm−1 and is assigned to lattice vibration. The most intensive infrared bands, located at 1209 and 1273 cm−1, are ascribed as in-plane modes (δ) of BOH. Bands associated with water bending mode (ν2) and stretching vibration (ν1) are observed at 1668 cm−1 (IR) and in the 3000-3500 cm−1 region (both Raman and IR spectrum). Thermal analysis showed differences between two research samples of larderellite connected with presence of adsorption water, that can indicate influence of conditions of minerals storage on properties of mineral.