Study on the effect of heat treatment on amethyst color and the cause of coloration.

ABSTRACT: The effect of heat treatment on amethyst color was studied from a new perspective of chromaticity of gemstones and the cause of amethyst coloration was discussed based on the results of X-ray diffraction, ultraviolet-visible spectroscopy. The results show that the amethyst color has no significant relationship with cell parameters but the crystallinity index decreases as temperature rises. The absorption band at 545 nm in the UV-visible spectrum can be related to a charge-transfer transition of Fe³⁺ and O^2-, which has a significant relationship with amethyst lightness and chroma. The color at different temperatures can be divided into three stages: The amethyst stage with temperature below 420 °C, the prasiolite stage with temperature between 420 and 440 °C where the

SUBMITTER: Cheng R 

PROVIDER: S-EPMC7483767 | biostudies-literature | 2020 Sep

REPOSITORIES: biostudies-literature