Crystallisation of processed nepheline syenite–magnesite glasses

Transparent glasses were prepared from processed nepheline syenite–magnesite mixtures. Incorporation of TiO2 in the base glasses changes the glass colour from white to amber or dark brown. Translucent porcelainous glass ceramics with white, creamy and a variety of bluish colorations were obtained in glasses containing non-magnetic nepheline syenite. However, dark marblelike glass ceramics were developed in glasses containing middling and tailing nepheline syenite. Aluminium diopside [Ca(Mg,Al)(Si,Al)2O6], nepheline, forsterite, magnesium titanate MgTi2O5 and hematite were developed by heat treatment of these glasses. SEM micrographs tend to show fine and uniform bulk with increasing Fe2O3 contents in the parent glass ceramic samples, however addition of TiO2 enhances nucleation and the microstructure becomes of evenly good uniform fine structure in the sample with lowest iron content.