Study of impurity in blue spinel from the Luc Yen mining area, Yen Bai province, Vietnam

Le Thi Thu Huong; Tobias Haeger; The-Long Phan

doi:10.15625/0866-7187/40/1/10915

Author affiliations

Authors

Le Thi Thu Huong 1- Faculty of Geology, VNU University of Science, 334, Nguyen Trai, Hanoi 2- Institut of Earth science, Karl Franzens University, Universitaetsplatz 2, 8010-Graz, Austria
Tobias Haeger Institute of Geosciences, Johannes Gutenberg University, 55099- Mainz, Germany
The-Long Phan Department of Physics, Hankuk University of Foreign Studies, Yongin 449-791, Korea

DOI:

https://doi.org/10.15625/0866-7187/40/1/10915

Keywords:

Blue spinel, impurity, coloration

Abstract

In this paper, we present the main impurities in natural blue spinel from the Luc Yen mining area in Yen Bai province, Vietnam. Together with identifying impurities and their valence, we have taken into account the site of some impurities in the MgAl₂O₄ spinel structure by using sensitive techniques, including Electron Microprobe Analysis (EMPA), UV-Vis-NIR, electron spin resonance (ESR), and X-ray absorption (XAS). EMPA results indicated that blue spinel contains different impurities, including V, Mn, Ni, Zn, Ti, Cr, Fe, Co and Ca. UV-Vis-NIR, ESR and XAS studies revealed that the oxidation state of Mn, Co, Fe and Ni is 2⁺ while that of Cr is 3⁺. Particularly, Co²⁺, Fe²⁺, and Cr³⁺ ions are identified to contribute to color variation in the blue spinel samples. Our study also indicated Co²⁺ and Cr³⁺ located in the octahedral position of Al³⁺ of the MgAl₂O₄ structure.

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