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Hearts of iron 3 tutorials5/24/2023 For example, garnets with a color-changing effect often have different colors when illuminated by different light sources. At the same time, there is often a link between the color of a gemstone and external factors. ![]() However, due to the limited number and type of samples, there are fewer studies on the color genesis of different colored spinels, and there is a lack of quantitative characterization of spinel color transitions and their causes. It has good color uniformity and is now mostly used in the study of gemstone chromaticity, such as beryl, peridot, turquoise, chrysoprase, jadeite, etc.Ī synthesis of previous research results shows that although the crystal structure, chemical composition, spectroscopic characteristics, color genesis and inclusion characteristics of spinel have been studied to some extent at present, the research methods have developed from general gemological tests and microscopic observation to the application of modern testing techniques. Chroma C* and hue angle h° can be calculated from color coordinates a*, b*. Hue angle h° represents a series of continuous color hue transitions. The larger the chroma value, the more vivid the color. Chroma C* represents the intensity of a single color of intensity, ranging from very light color (C* = 0) to very intense color (C* = 100). Color coordinate a* describes the color change between red (+a*) and green (−a*), while color coordinate b* describes the color change between yellow (+b*) and blue (−b*). ![]() The higher the value of lightness, the brighter the color. Lightness L* represents the degree of lightness of a color, ranging from very dark black (L* = 0) to very bright white (L* = 100). The CIE 1976 L*a*b* color uniform space is the latest recommendation by the International Commission on Illumination for a table color system for quantitative color characterization with lightness L*, color coordinates a* and color coordinates b* as color parameters. In recent years, chromaticity has played an important role in gemmological research. The lightness L* of spinel decreases with increasing Cr content, and the hue h° decreases with increasing Fe and increases with increasing V content. Spinel can be divided into iron-bearing spinel and chromium–vanadium-bearing spinel according to their chromogenic elements, where Fe is mostly present in the form of Fe 2+, which is mainly replaced with Mg 2+ in tetrahedral voids, while Cr 3+ and V 3+ are mainly replaced with Al 3+ in octahedral voids, and the level of Al content indicates the degree of isomorphism in spinel. The results show that the chroma C* is mainly controlled by the variation of color coordinates a*, and the hue angle h° is mainly controlled by the variation of color coordinates b*. In this paper, the chemical composition and spectroscopy of 38 violet-red to orange-red spinel samples were analyzed by energy dispersive X-ray fluorescence spectrometer and UV-visible spectrophotometer, based on CIE LAB color space, to explore the effects of different chromogenic ions on spinel color transition.
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