Optical and Structural properties of Gemmological materials used in works of Art and Handicraft

Disorder phenomena related to formation conditions of natural and synthetic spinels, both stoichiometric (MgO·Al2O3) and those exhibiting different Al/Mg ratios, are investigated by photoluminescence spectroscopy. The same approach appears to be less adequate when dealing with more complex materials, such as beryls (3BeO·Al2O3·6SiO2). On the other hand, Raman spectroscopy allows easy identification of different varieties of beryls and of their inclusions, together with that of widely used imitations. The above techniques are totally non-destructive and do not require any treatment of the samples. The apparatus developed at our laboratories allows investigation of irregularly shaped samples within a large range of sizes.