Infrared and chemical characterization of natural amethysts and prasiolites colored by irradiation

Materials Research

Fernando Soares Lameiras²  Eduardo Henrique Martins Nunes¹  Wander Luiz Vasconcelos¹ 

[1] ,Centro de Desenvolvimento da Tecnologia NuclearBelo Horizonte MG ,Brazil

关键词: amethyst;    prasiolite;    infrared spectrum;    irradiation;    trace elements;   

DOI  :  10.1590/S1516-14392009000300011

来源: SciELO

【 摘 要 】

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+]º and [FeSiO4/h+]º 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.

【 授权许可】

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