Influence of Temperature on Surface Colouration of the Lead Oxide Treated Natural Gem Ruby

Abstract

Odisha is endowed with gemstone resources but most of them do not get a good market because of poor lustre, unattractive colour and defective nature. Generally heat treatment is carried out to enhance the colour and clarity of such low grade ruby stones. Some chemical additives are also added during the heat treatment for crack healing and subsequent clarity improvement. Attempt has been made by the authors to enhance the aesthetic value of natural occurring gem variety ruby from Nuapada district, Odisha through heat treatment and oxide filling and the results are reported. Natural occurring ruby stones having defects were surface cleaned and heat treated at different temperatures with lead oxide filling to show improvement in colour and clarity. The gem rubies before and after treatment were characterised by SEM and XRD to observe the nature of pore filing and sticking behaviour of lead dioxide in to the ruby matrix. Photo luminescence and Raman spectroscopy studies were carried out to obtain the ruby phase confirmation along with the change in optical characteristics of gem rubies after heat treatment.