| The decomposition of pure chrysotile from Thetford, Quebec heated at constant temperature in air from 200--1000°C for 4 to 720 hours was studied by using X-ray diffraction and optical microscopy techniques. No morphological changes were observed optically below 450°C and 24 hours, although X-ray diffraction data suggest that chrysotile degrades then recrystallizes below 450°C. Throughout the temperature range of 500--1000°C, changes in the refractive indices observed included several cycles of increasing and decreasing magnitudes and ranges. Chrysotile was no longer present above 575°C and 24 hours. The lowest temperature of forsterite appearance was at 500°C and 720 hours and the lowest temperature of enstatite appearance was at 800°C for 8 hours. Broad reflections were observed within 500--750°C at 16--8A, 4A, and 3A spacings. These reflections suggested the possible presence of talc and tridymite-like mineral phases. X-ray diffraction and optical microscopy results of this study show that the decomposition of chrysotile is more complex than previously understood. |
