Composition and properties of glass obtained from Early Cretaceous Sidi Aich sands (central Tunisia)

The present work describes the chemical–mineralogical characterization of Barremian sand deposits. These Sidi Aich sands are observed exclusively in central Tunisia; in the Central Atlas two major domains might be discriminated: north–south axis and southern Atlas. In the collected raw samples, quartz and potassic feldspars are depicted with percentages that reach 30 wt.%. The chemical and XRD analyses confirm the existence of K-feldspars. These compounds are known fluxing agents. Since the amount in heavy minerals (<0.36 wt.%) and Fe2O3 (<0.71 wt.%) is relatively low, their interest for glass manufacturing is high. In accordance, semi-industrial tests were carried out to produce glass. The obtained bodies were investigated by XRD, attempting to detect the crystalline phases that can appear and influence the technological behaviour of these glasses. Mechanical properties distinguished SMS and SAT glasses when the others are conditioned by microfractures that could be related to annealing stage. The investigation also concerned the colours exhibited by final products (green to amber). This aspect is dependent on the amount of iron and its redox states; ferrous (Fe2+)/ferric iron (Fe3+) which is here detected in UV–vis–NIR spectra of different tested glasses.