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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
|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.|
|Appears in Collections:||Artigo de periódico|
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