Study on the Color-Influencing Factors of Blue Iolite

Abstract

This article explores the factors that influence the color of blue iolite, which is the gem-quality variety of the cordierite mineral. The X-Rite SP62 portable spectrophotometer was used to measure color in the CIELAB color space. ED-XRF and UV–vis were used for analysis. The results show that blue iolite contains the chromophore elements Fe and Mn, but the effect on the color of iolite is not significant due to the low Mn content. The lightness L* and the hue angle h° are mostly determined by its Fe content. UV–vis spectra show that iolite has a broad absorption band near 570 nm caused by the charge transfer between Fe2+ on the octahedron and Fe3+ on the T11 tetrahedron and results in the color of blue iolite. Each different standard light source has different degrees of influence on the color parameters of iolite, and the hue angle h° is the most influenced.