Abstract The effect of heat treatment on amethyst color was studied from a new perspective chromaticity gemstones and the cause coloration discussed based results X-ray diffraction, ultraviolet–visible spectroscopy. show that has no significant relationship with cell parameters but crystallinity index decreases as temperature rises. absorption band at 545 nm in UV–visible spectrum can be related to charge-transfer transition Fe 3+ O 2− , which lightness chroma. different temperatures divided...

This study explores the factors influencing body color of kyanites and chromogenic mechanism from a novel perspective gemstone chromaticity. The gemological properties 20 samples Coronel Murta, Minas Gerais, Brazil, were characterized using spectrophotometer, Fourier-transform infrared spectroscopy (FTIR), ultraviolet-visible (UV–Vis). results indicate that Fe content in significantly affects hue angle h°, chroma C*, colorimetric coordinate b*, with higher concentrations resulting deeper...

Abstract We tested 288 pieces of the polished cabochon jadeite‐jade with high quality green and smooth surfaces using colorimeter Color i5 based on CIE 1976 L*a*b* uniform color space. The changes after alternating three standard light sources D 65 , A CWF were compared, degree metamerism was evaluated. results show that increase chroma turn bluish into vivid green, which are similar or to nearly colorless transparent glass‐like samples fine textures. When individually alternated, lightness...

Peridot's yellowish-green color is not only produced by ${{\rm Fe}^{2+}}$Fe2+ but also influenced background, observer, illuminance, and temperature of the light source. In this research, we studied most effective background for peridot grading under a 6504K fluorescent lamp. Ninety-five gem-quality samples from China, Pakistan, Myanmar were using electron probe micro-analyzer, spectrophotometer, Munsell neutral gray backgrounds, standard gold alloy backgrounds. The results provided effects...

Abstract Previous research indicated that the peridot's color is dominated by selective absorption of visible light caused ferrous ion, hue angle which in an inverse ratio concentration Fe 2+ . This article focuses on effect peridot under different standard sources based CIE1976 L*a*b* space system and round RGB diagram tries to find best one for its grading display. Based results a series experiments, including electron microprobe analysis, spectrophotometer, UV‐Vis spectrum, illumination...

Thirty-five gem-quality turquoise samples with various colours were investigated using energy-dispersive X-ray fluorescence spectroscopy, ultraviolet–visible Fourier-transform infrared spectroscopy and scanning electron microscopy. Sample chemical spectral analyses indicate that Fe 3+ contributes to green hue of turquoise, whose absorption band exhibits a bathochromic shift from 426 428 nm increasing V content in the solid-solution series turquoise-chalcosiderite. enhances blue orange...

A colour-changing garnet exhibits the “alexandrite effect”, whereby its colour changes from green in presence of daylight to purplish red under incandescent light. This study examines this species garnets as well causes change by using infrared and ultraviolet visible (UV-Vis) spectroscopy. The spectra show that paper belong solid solution pyrope-spessartine type. CIE1931 XYZ matching functions are used calculate parameters influencing different light sources. UV-Vis two zones transmittance,...

With the help of irradiation, [FeO4]4− was excited by one electron from ferric electronic shell, it absorbed visible light 550 nm, and then made crystal appears golden color which named citrine. 27 pieces citrine confirmed as natural 32 IR technology, their parameters were calculated colorimeter tests, how could hue, lightness chroma contribute to visual analyzed too. It reveals that citrines are negatively correlated with hue lightness, control angle on impact chroma, co-effect produce...

Chrysoprase is a popular gemstone with consumers because of its charming apple green colour but scientific classification has not yet been achieved. In this research, we determined the most effective background Munsell Chart for chrysoprase grading under 6504K fluorescent lamp and applied an affinity propagation (AP) clustering algorithm to coloured gems first time. Forty gem-quality samples from Australia were studied using UV-VIS spectrophotometer neutral grey backgrounds. The results...

Abstract The genesis and influencing factors of the colour chrysoprase were studied based on results transmission electron microscopy X-ray fluorescence, ultraviolet–visible Raman spectroscopies. show that under a 6504-K fluorescent lamp, is divided into grades fancy, fancy intense deep. lightness affected mainly by its chromium content, chroma nickel content hue angle sum ferrum contents. related significantly to window occurs between two main bands centred at 380 660 nm absorption peaks in...

This paper introduces computer vision systems (CVSs), which provides a new method to measure gem colour, and compares CVS colourimeter (CM) measurements of jadeite-jade colour in the CIELAB space. The feasibility using for measurement was verified by an expert group test reasonable regression model experiment involving 111 samples covering almost all colours. In test, more than 93.33% images are considered have high similarities with real objects. Comparing L*, a*, b*, C*, h, ∆E* (greater...

The corrected ultraviolet-visible light spectrum was used to calculate the color of synthetic rubies with different path lengths, and influence length standard source on ruby studied. results show that difference in colour between o direction e decreases as increases. At same time, increases, lightness L* decreases, hue angle h° chroma C* first increases then begins decrease under continuous lightness. ΔE*ab reaches maximum when is around 10 mm, has greatest ΔE*ab. As continues increase,...

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

Fluorescence plays an important role in determining the color appearance of fluorescing minerals. This paper discusses mechanism red spinel and effects from light source as well background on color. Excitation-Emission Matrices (EEMs) fluorescence spectroscopy was utilized to characterize natural Cr-doped magnesia-alumina Myanmar. EMP, LA-ICP-MS, optical were applied study spinel's chemical compositions mechanism. X-Rite Ci-7800 spectrophotometer, which is useful measure colors for minerals,...

The chromaticity characterization and influencing factors of the body color 28 yellow-green opals were studied through Fourier transform infrared spectrum (FTIR), energy-dispersive X-ray fluorescence spectroscopy (ED-XRF), ultraviolet-visible (UV-vis) X-Rite SP62 spectrophotometer. It was found that hue h° iron content opal highly negatively correlated, chroma C* sum nickel significantly positively lightness L* correlated with chromium content. light green is mainly caused by nickel. will...

This study reports the effects of transition metal ions on colour blue-green beryl. Industrial cameras were used to measure in CIELAB space. X-ray fluorescence (XRF), diffraction (XRD), infrared spectroscopy (IR), and ultraviolet-visible (UV–vis) for characterization. The d–d Fe3+ with sixfold coordination, O2−→Fe3+ charge transfer, binuclear M–M complexes formed by [Fe2(OH)4]2+ channel caused a yellow tone, whereas transfer Fe2+/Fe3+ coordination tone. chroma beryl was negatively correlated...

This study reports the characteristics of water in channels blue-green beryl and its effect on color. An industrial camera was used to measure color CIELAB space. X-ray fluorescence (XRF), diffraction (XRD), infrared spectroscopy (IR), ultraviolet-visible (UV–vis) spectroscopy, silicate rock chemical analysis method were for analysis. The peaks at 5105 cm−1 5269 combination tone type II water, which negatively correlated with b*, positively peak area 3162 (Na–H) cell parameter a0. 7097 7142...

Abstract The chemical composition and influencing factors of the colour 95 yellow to light blue iron-bearing beryl are studied through Electron Microprobe Analysis (EMPA), Energy-dispersive X-ray fluorescence (ED-XRF) spectroscopy, Fourier transform infrared (FTIR) ultraviolet–visible (UV–vis) spectroscopy X-Rite SP62 spectrophotometer. intensities three characteristic hydroxyl stretching bands from 3500 cm −1 3800 prove they low medium levels alkali bearing natural beryl. wide absorption...

The color-changing garnet displays the “alexandrite effect”, changing from green in daylight to purplish-red under incandescent light. mineralogical characteristics of is analyzed using Raman spectroscopy, ultraviolet-visible (UV-Vis) an electron probe, and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). color garnets with different thicknesses was calculated International Commission on Illumination (CIE 1976) L * a b uniform system. results revealed presence rutile...

The purpose of this paper is to investigate the standard light source for grading and displaying color red jadeite classify color. With Raman spectrometer, ultraviolet-visible spectrophotometer X-ray fluorescence results show that, Fe 3+ main chromogenic mineral jadeite, which negatively correlates with tonal angle, while has a positive correlation hematite content. 120 samples was examined by collecting reflective signaled from sample surface using an integrating sphere portable X-Rite SP62...

The application of digital imaging to color measurement is more and extensive, which also provides new ideas for gemology. In this paper, the single-factor experiment method orthogonal design are used study influence parameters system (DIS) on gem measurement. Among them, illuminance has most significant impact results, followed by exposure time, change distance an insignificant results; through range analysis variance, suitable red jadeite 1600 lx, 12,500 μs, 25 cm.

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 UV-visible spectrophotometer, based on CIE LAB color space, explore effects different chromogenic ions transition. The results show that chroma C* is mainly controlled variation coordinates a*, hue angle h° b*. Spinel can be divided into iron-bearing chromium–vanadium-bearing according their elements, where Fe mostly present...