Abstract
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.
Highlights
The silicate materials are of special interest for science and technology due to their wide applications in optical and semi-conductor devices [1]
Aluminum occupies the slightly distorted M1 site, which is octahedrally coordinated with an average metal oxygen distance of 1.92Å; while the M2 site is occupied by Li, which is six-fold coordinated with an average metal-oxygen distance of 2.23Å [3,4]
The results show that the concentration of Mn is higher in kunzite as compared to Fe
Summary
The silicate materials are of special interest for science and technology due to their wide applications in optical and semi-conductor devices [1]. Spodumene (LiAlSi2 O6 ) is widely utilized in ceramics and glass manufacturing and is an important source of Li. Spodumene (LiAlSi2 O6 ) is widely utilized in ceramics and glass manufacturing and is an important source of Li It is a member of the pyroxene mineral group and normally the stable low-temperature type of spodumene (α-spodumene) crystallizes in a monoclinic crystal system with space group C2/c. M1 and M2 in the same crystallographic plane [2]. There is only one type of tetrahedral site, which is completely occupied by silicon in pyroxene and is not involved in producing colors. O(1) , O(2) and O(3) are three crystallographically non-equivalent
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