Aspects of the production of ornamental stone plates with fragments of hyaline quartz and the potential for color development from irradiation combined with heat treatment

Abstract

The present work refers to a study on the production of dimension stones slabs with hyaline quartz and its potential for color development through irradiation combined with heat treatment. The research included technical visits to a company that produces slabs (combining parts of sliced quartz crystals) for the dimension stone industry, where the stages of slabs production were described. The material used was classified as a colorless hyaline quartz, with the presence of partially healed fractures and monophasic fluid inclusions, that need more attention when in the heat treatment. The study evaluated the potential for color development through combined irradiation and thermal treatments, using analyses at the Federal University of Espirito Santo - UFES gem and characterization laboratory and at the infrared spectroscopy laboratory at the Nuclear Technology Development Center - CDTN. The results showed that hyaline quartz fragments can develop characteristic colors depending on the irradiation dose and heat treatment. If they have homogeneous behavior in relation to the spectral analysis, the crystals can develop characteristic colors from a weak green gold (yellow-green) to yellow and brown, keeping the proper irradiation doses (yellow-green, 60-100 kGy; yellow, 100- 200kGy and brown >200kGy), but such colors would still have to be submitted for verification of acceptance by the dimension stone market.