Gemmological and Spectral Characteristic of Ruby from Yen Bai, Vietnam

One of the ruby deposits of important economic value in Southeast Asia is located near the city of Luc Yen, Yen Bai, North Vietnam. Ruby samples were collected in local deposits associated to marble from Yen Bai, Vietnam. According to the colour characteristics, the samples were divided into four categories:Light purplish red, purplish red, dark red, and orange. In this paper, the authors studied the gemmological and spectral characteristics of ruby samples from Yen Bai by conventional gemmological tests, EDXRF, Fourier transform infrared spectroscopy, Raman spectroscopy, and ultraviolet-visible spectrometry. The results indicated that the rubies belong to marble, which show a typical crystal form of hexagonal tabular. Besides, the variety of fluid inclusions ould be observed by microscope, and some samples show the typical single blue zone of ruby from Vietnam. It shows the five intrinsic infrared absorption bands of ruby, and some are ascribed to O-H stretching vibration. Raman bands are mainly associated with the bending vibrations and stretching vibrations ofAlO₆. Based on UV-Vis spectroscopy in combination with the component analysis, the four main colours can be separated by quantifying dominant wavelength, complementary dominant wavelength, and colour purity of the rubies from Yen Bai, Vietnam.