Experimental Study of High-Temperature Transformations in Charoitites

Abstract

This paper reports the investigation of transformations occurring during heating of charoite minerals. Charoite rocks with different color characteristics (lilac, brown, and white asbestiform charoite referred to as charoite-asbestos in the Russian literature) were investigated using mass spectrometry, differential scanning calorimetry and thermogravimetry (DSC–TG), scanning electron microscopy (SEM), X-ray diffraction, and Raman spectroscopy. The charoites were heated up to 1200°C. During heating, dehydration and dehydroxylation of lilac, brown, and white charoites were observed in the temperature range 50–500°C. The release of H₂O and OH-groups with an endothermic effect of ΔH = 58 J/g was also detected in white charoite-asbestos at 720–800°C. Our study demonstrated that charoite gradually transforms to wollastonite and, then, to pseudowollastonite at temperatures above 900°C.