Dehydroxylation and Ostwald ripening effects in roofing slates

Roofing slates only open in wet and when they are maintained in wet from qu arry. Their irreversible drying could be explained by the closure of porosi ty following Ostwald ripening processes of illite along the slaty cleavage interface-interphases along with the leaking out water-alkali solutions. Ro ofing slate drying randomly produces swelling of layers and crystallite coa lescence. They have been detected huge deformations of the illite-chlorite XRD 10 Angstrom peak by isothermal scanning (i.e., 95 degrees C) of XRD und er thermo-photonic stimulation and electronic control of temperature. These large anomalies of the illite crystallinity peak working with aliquots of slate prevent against the petrological use of the Kubler index using the sl aty cleavage of micro-mono-blocks. The slate also shows a continuous distri bution of thermoluminescence traps with maxima concentration in 300 degrees C, which could be attributed to the creation-annihilation of [AlO4/alcali] (+) y [AlO4](o) centres. The convergent trend of thermoluminescence glow cu rves of preheated aliquots, circa 475 degrees C, coincides with the theoret ical maxima of dehydroxylation temperature.