Paraíba or Not? Cu-bearing Tourmaline with a Distinct Fe Concentration

Chemical variations among these three samples are best revealed by comparing the concentrations of their chromophores Cu and Fe (Table I), as measured by laser ablation inductively coupled plasma time-of-flight mass spectrometry (LA-ICP-TOF-MS) using SSEF’s GemTOF system (see Wang et al. 2016). The...

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Bibliographic Details
Published inJournal of gemmology (1986) Vol. 38; no. 1; pp. 20 - 22
Main Authors Krzemnicki, Michael S., Wang, Hao A. O.
Format Journal Article
LanguageEnglish
Published London The Gemmological Association of Great Britain 2022
Subjects
Color
Mass spectrometry
Trace elements
Nigeria
Namibia
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Summary:Chemical variations among these three samples are best revealed by comparing the concentrations of their chromophores Cu and Fe (Table I), as measured by laser ablation inductively coupled plasma time-of-flight mass spectrometry (LA-ICP-TOF-MS) using SSEF’s GemTOF system (see Wang et al. 2016). The colour of the intermediate Fe-Cu tourmaline (sample B) is related to the absorption bands of both Cu2+ and Fe2+. Because the bands at 700 and 900 nm have nearly equal intensity in this sample, it can be deduced that its colour is due to a combination of Cu and Fe. See PDF.] Based on statistical processing of the trace-element data with a machine-learning algorithm (unsupervised non-linear t-SNE; Wang & Krzemnicki 2021), the origin of the intermediate Fe-Cu tourmaline (sample B) is in our opinion most likely Nigeria, although an independent confirmation of the mining site is still pending.
ISSN:1355-4565
2632-1718
DOI:10.15506/JoG.2022.38.1.20