Ornamental stone finished product aesthetic inspection and characterization through a digital spectrophotometric approach

Many manufactured good products present different market characteristics according to their pictorial aspects. Such aspects usually depends from many factors: in some cases they are related to the adopted production process, in other cases they are intrinsically linked to the handled material characteristics. Ornamental stone represent a typical example, where both the two previous mentioned factors have to be considered. Both the aspects, in fact, are of primarily importance to certify, in pictorial terms, the aesthetic attributes of slabs, tiles and, in general, of ornamental and/or dimensional stone based products. The study was mainly addressed to investigate the possibility to develop a methodology and a technique to measure the quality of the polished stone samples, evaluating at the same time, the effect of polishing on the final detected stone surface pictorial attributes. To reach such a goal a specially designed probe holder, together with computer generated spectrum analysis techniques, has been developed and measurements were made on various rock samples to quantify, independently from stone surface pictorial attributes, as color and texture, stone surface degree of polishing. The obtained results allowed to quantify the correlation existing between stone characteristics (constituting minerals, texture, structure) and surface status after different polishing actions.