New insights into the crystal chemistry of sauconite (Zn-smectite) from the Skorpion zinc deposit (Namibia) via a multi-methodological approach

Abstract A multi-methodical characterization of a sauconite (Zn-bearing trioctahedral smectite) specimen from the Skorpion ore deposit (Namibia) was performed by combining X-ray powder diffraction (XRPD), cation exchange capacity (CEC) analysis, differential thermal analysis (DTA), thermo-gravimetry (TG), Fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM-HRTEM-AEM). The pattern exhibits typical features turbostratic stacking disorder with symmetrical basal 00l reflections long-tailed hk bands, as confirmed TEM observations. Besides sauconite, sample contains minor amounts kaolinite, dioctahedral smectite, quartz. CEC provides total Ca (~69%), Mg (~26%), Na (~4%), K (0.7%) exchangeable cations. Therefore, Zn is located exclusively within octahedral site sauconite. TG yields mass loss about 17%. Three endothermic peaks can be observed in DTA curve, associated dehydration dehydroxylation material. An exothermic peak at 820 °C also present consequence decomposition recrystallization. spectrum shows Zn3OH stretching signature 3648 cm–1, whereas, OH/H2O region two bands 3585 3440 cm–1 attributed to vibrations inner hydration sphere interlayer cations absorbed H2O vibration, respectively. Diagnostic kaolinite impurity ~3698 3620 are found, whereas 2:1 layer silicates may contribute bands. Finally, using one-layer supercell approach implemented BGMN software, satisfactory XRPD profile fitting model for obtained. These findings have implications not only economic geology/recovery critical metals but also, more generally, field environmental sciences.