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Open AccessArticle

An X-ray Absorption Near-Edge Structure (XANES) Study on the Oxidation State of Chromophores in Natural Kunzite Samples from Nuristan, Afghanistan

1
Gemmological Institute, China University of Geosciences, Wuhan 430074, China
2
Gems & Jewellery Centre of Excellence, University of Engineering & Technology Peshawar, Peshawar 25120, Pakistan
3
Private Scientific Consultant, D-24558 Henstedt-Ulzburg, Germany
4
Department of Jewelry Technology, Dahan Institute of Technology, Hualian, Taiwan
5
Synchrotron Light Research Institute, 111 University Avenue, Muang, Nakhon Ratchasima 30000, Thailand
*
Author to whom correspondence should be addressed.
Minerals 2020, 10(5), 463; https://doi.org/10.3390/min10050463
Received: 26 April 2020 / Revised: 16 May 2020 / Accepted: 17 May 2020 / Published: 20 May 2020
(This article belongs to the Special Issue X-ray Absorption Spectroscopy of Synthetic and Natural Minerals)
Kunzite, the pink variety of spodumene is famous and desirable among gemstone lovers. Due to its tenebrescent properties, kunzite always remains a hot research candidate among physicists and mineralogists. The present work is continuing the effort towards value addition to kunzite by enhancing its color using different treatments. Before color enhancement, it is essential to identify the chromophores and their oxidation states. In this paper, the authors investigated the main impurities in natural kunzite from the Nuristan area in Afghanistan and their valence states. Some impurities in the LiAlSi2O6 spodumene structure were identified and quantified by using sensitive techniques, including Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS), UV−VIS and X-ray absorption near-edge structure (XANES). LA-ICP-MS indicated many trace elements as impurities in kunzite, among which Fe and Mn are the main elements responsible for coloration. The oxidation states of these two transition elements were determined by the XANES technique. The study reveals that Mn is present in both Mn2+ and Mn3+ oxidation states, while Fe is present only in Fe3+ oxidation state. View Full-Text
Keywords: kunzite; oxidation state; XANES; LA-ICP-MS; UV−VIS kunzite; oxidation state; XANES; LA-ICP-MS; UV−VIS
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MDPI and ACS Style

Rehman, H.U.; Martens, G.; Tsai, Y.L.; Chankhantha, C.; Kidkhunthod, P.; H. Shen, A. An X-ray Absorption Near-Edge Structure (XANES) Study on the Oxidation State of Chromophores in Natural Kunzite Samples from Nuristan, Afghanistan. Minerals 2020, 10, 463.

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