Abstract:

Twenty four chrysoberyl and alexandrite samples from the major deposits all over the world were studied qualitatively by XRF and the trace elements in chrysoberyl were gotten mainly to be Fe, Ga, Ti, in alexandrite to be Fe, Cr, Ti.Half quantitative analysis of SRXRF experiments were carried out on one chrysoberyl and one alexandrite, the results indicated that in chrysoberyl Fe concentration averaged to be 17,800×10^-6, Cr 855×10^-6; in alexandrite Fe concentration averaged to be 16,060×10^-6, Cr 13,333×10^-6; and Ga was one of the very important impurity in chrysoberyl only less than Fe concentration Optical absorption of 15 samples indicated that the absorption of chrysoberyl was induced by Fe³⁺ ion, of alexandrite by Fe³⁺ and Cr³⁺ together.Series chromaticity calculations were processed. The calculation results indicated that the optical spectrum which had the 540-630 nm broad absorption band and the 440-470 nm maximum absorption would induce red to green colorchange alexandrite effect, so the treatments of alexandrite may work in the direction of getting such a visible spectrum.

Key words: chrysoberyl, alexandrite, color, Fe³⁺ ion, Cr³⁺ ion, optical absorption