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Title: Infrared and chemical characterization of natural amethysts and prasiolites colored by irradiation
Title of periodic: Materials Research São Carlos
metadata.dc.title.subtitlejournal: Ibero-american Journal of Materials
Authors: Lameiras, Fernando Soares
Nunes, Eduardo Henrique Martins
Vasconcelos, Wander Luís
Affiliation: Centro de Desenvolvimento da Tecnologia Nuclear/CDTN, Belo Horizonte, MG, Brasil
Lamil Lage Minérios Ltda, Pará de Minas, MG, Brasil
Universidade Federal de Minas Gerais/UFMG, Belo Horizonte, MG, Brasil
Issue Date: 2009
Keywords: Amethysts;prasiolite;minerals;irradiation;trace amounts;infrared spectra
Abstract: The infrared bands of amethyst and prasiolite samples from different origins were correlated to the trace elements contents. Amethysts have an iron content greater than 20 ppm and a low content of sodium and potassium. Prasiolites have an aluminum content greater than 120 ppm and a higher overall trace elements content, which accounts for a strong absorption between 3200 and 3600 cm-1. Colorless samples of quartz that become amethysts and prasiolites after irradiation have infrared spectra at room temperature with a broad band at 3441 cm-1 and a sharp band at 3595 cm-1. The broad band splits in several bands at low temperatures that are related to AlSi and FeSi. The color of amethysts and prasiolites are assigned to [AlSiO4/h+]0 and [FeSiO4/h+]0 centers formed by the exposure to ionizing irradiation and to the influence of lattice distortions due to the content of iron as a substitute for silicon and a high content of trace elements of large ionic radius like potassium.
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Appears in Collections:Artigo de periódico

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