Comparative Study of Unheated and Heated Rubies from Myanmar

A batch of unheated and heated rubies from Myanmar were obtained from a gemstone processor in Thailand. The gemmological characteristics, chemical composition characteristics, infrared spectrum characteristics and UV-Vis absorption spectrum characteristics were tested and analyzed, so as to obtain the characteristics of the rubies after heat treatment and distinguish them from the unheated rubies from Myanmar. The test results showed that a large number of secondary melt inclusions were found in the heated rubies, while only mineral crystal inclusions and fluid inclusions were observed in the unheated rubies. In terms of chemical composition characteristics, the average content of Ti element in heated rubies is about 1 000 ppm higher than that in the unheated rubies, and the average content of Fe element in heated rubies is about 100 ppm lower than that in the unheated rubies. Absorption peaks of daspore, structural water and free water can be detected in unheated rubies, but these characteristic absorption peaks can not be detected in heated rubies due to the damage of high temperature. Compared with unheated rubies, the fluorescence peak of heated rubies near 694 nm is stronger and sharper.