Thermal behaviour of actinolite asbestos

Actinolite is one of the six minerals belonging to the group of asbestos minerals. There is increasing concern regarding the potential health risks from exposure to naturally occurring asbestos and asbestos-containing materials. The correct distinction of the fibrous asbestos minerals is very important not only from a scientific point of view, but also from a legislative perspective. Asbestos actinolite is currently the only asbestos mineral that has not been fully characterized from the thermal point of view. In order to compensate for this gap in scientific literature, this paper discusses the thermal behaviour of actinolite asbestos using thermogravimetric and differential scanning calorimetry. X-ray powder diffraction, Scanning and Transmission Electron Microscopy combined with energy-dispersive spectrometry were used for the characterization of actinolite fibres before and after heating at 1000 and 1200 °C in order to determine their resistance to high-temperature changes and the products of thermal recrystallization. Actinolite asbestos breaks down at approximately 1030 °C. The thermal decomposition process of actinolite asbestos consists of two distinct events followed by recrystallization into new stable crystalline phases which preserved the original fibrous morphology (known as pseudomorphosis). The thermal analysis may prove to be useful for actinolite identification and discrimination, particularly in the case of natural massive samples where asbestos tremolite–actinolite amphiboles are mutually intermixed. Furthermore, profound knowledge of the thermal behaviour of this asbestos mineral may provide us with the relevant data for understanding the crystal–chemical transformations of asbestos through thermal inertization treatment.