Coloration Mechanism Research Articles

Influence of cobalt specialization state on color mechanism and ‘color dispersion’ behavior of blue-and-white porcelain

Ancient blue-and-white porcelains exhibit wide color variations and ‘color dispersion’ due to the use of different cobalt-based blue pigment in different periods. Nowadays, it is difficult to date back due to cobalt ore raw material exhaustion. To clarifying the wide color variations and ‘color dispersion’, Field emission scanning electron microscopy (FE-SEM), X-ray absorption fine structure (XAFS), Optical Microscope (OM), etc, were used to study the color mechanism and ‘color dispersion’ behavior of blue-and-white porcelain by comparing cobalt speciation state and crystal structure stability. The blue tones of blue-and-white porcelain are mainly due to Co2 + ions located in the tetrahedron structure in the glaze, and thus the ‘color dispersion’ distance is large. when Co2+ is located in the tetrahedral structure of the spinel crystal, the blue-and-white porcelain appears dark blue and thus the ‘color dispersion’ distance is small.

Development Mechanism of Flower Type and Color in Tree Peony: A Review

Development Mechanism of Flower Type and Color in Tree Peony: A Review

Targeted metabolomics- and transcriptomics-based investigation of carotenoid pigmentation in Phalaenopsis-Type Dendrobium hybrids

Phalaenopsis-type Dendrobium hybrids (Den-Phals) stands out as globally popular tropical orchids. Carotenoids are crucial colored phytochemicals in flowers. The coloration mechanism of carotenoids in Den-Phals flowers were investigated through targeted metabolome and transcriptome analyses. In total, 48 carotenoids were detected from 11 Den-Phals. The composition and content of carotenoids varied among these cultivars and in the different parts of the same flowers. Lutein, which improves human visual performance, had the largest content in all the samples, with an average of 52.46%, and the highest value reached 79.45%. The top 10 carotenoids, including lutein, β-carotene, neoxanthin, iolaxanthin, (E/Z)-phytoene, zeaxanthin, antheraxanthin, α-cryptoxanthin, β-cryptoxanthin, and α-carotene, collectively constituted 90% of the total carotenoids content. Among them, β-carotene, rather than lutein, was correlated with the yellow hue of floral color and was considered a key pigment. Furthermore, transcriptome sequencing of two cultivars with significant difference in carotenoid contents inferred the carotenoid metabolic pathway in Den-Phals. Seven differentially expressed genes (DEGs) were isolated: phytoene synthase (PSY), carotenoid isomerase (CrtISO), ζ-carotene isomerase (Z-ISO), lycopene ε-cyclase (LCYE), β-carotene hydroxylase (BCH), zeaxanthin epoxidase (ZEP), and 9-cis-epoxycarotenoid dioxygenase (NCED). Among these, LCYE was deemed a crucial enzyme gene, as it appears to govern lutein or β-carotene accumulating, thereby influencing yellow coloration of Den-Phals. The results offer valuable understanding of the carotenoid metabolic pathway and provide new guidance for breeding Den-Phals cultivars having both ornamental and medicinal traits.

The Coloring Mechanism of Opaque Glazes from the Changsha Kiln of the Tang Dynasty

The Changsha Kiln of the Tang Dynasty was a major site for celadon production, yet the mechanisms behind the unique coloring of its opaque glazes remain inadequately explored. Prior research has largely focused on the general composition of these glazes, with limited understanding of the specific processes contributing to their distinct visual characteristics. This gap in knowledge hinders efforts to accurately replicate these historical glazes and fully appreciate their technological significance. In this study, we analyze the chemical composition and microstructure of opaque glaze specimens from the Changsha Kiln using advanced techniques such as EDXRF, SEM-EDS, and ultra-deep field microscopy. Our findings reveal that the opaque glazes are high-calcium compositions where phase separation and the presence of coloring ions like Cu2+, Cu+, and Fe3+ play critical roles in determining the glaze’s color. The interplay between chemical coloring and phase separation processes is shown to produce the distinct blue-green and creamy white hues observed in the glazes. These results provide a deeper understanding of the coloring mechanisms in Changsha Kiln glazes, contributing to the broader field of ceramic research and aiding in the preservation and accurate reproduction of these historic artifacts.

Transcriptome sequencing and SSR prediction of Clematis calyx based on SMRT sequencing platform

Clematis is an excellent vertical greening plant for garden viewing vines, with great ornamental and high medicinal value. To obtain transcriptome information and functional gene data for the Clematis calyx, this study utilized three biological replicates of the calyx from each of the three Clematis varieties: ‘Henryi’, ‘Polish spirit’, and ‘Mme Julia Correvon’ Single-molecule real-time sequencing technology was employed for full-length transcriptome sequencing. The study revealed that 21,673,173 non-chimeric sequences were identified through full-length transcriptome sequencing. After clustering, correction, and redundancy removal, 40,465 high-quality, full-length transcripts were obtained. Among these transcripts, there were 15,488 long non-coding RNA (lncRNA), 9,212 simple sequence repeats (SSR) sites, 1,247 transcription factors (TFs), 1,228 alternative splicing events, and 7,189 selectively polyadenylation sites predicted. In addition, 7,442 primer pairs were designed based on the SSR sites, covering 80.76% of the total SSR. 15 primer pairs were randomly selected for amplification, and 73.3% of them were successfully amplified. Transcript annotation results showed that 38,439, 38,094, 26,815, and 33,407 transcripts were annotated to the Nr, KEGG, KOG, and SwissProt databases, respectively. Among these, the KEGG database identified 137 metabolic pathways, including biosynthesis of secondary metabolites, carbon metabolism, and amino acid biosynthesis. 104 and 7 transcripts are involved in the flavonoid and anthocyanin metabolism pathways, respectively. The above results provide initial insights into the transcriptome information and functional characteristics of Clematis calyx. This critical data supports future research on marker primers for the color mechanism of Clematis calyx, the pathways and regulatory mechanisms of flavonoids and other products, as well as specific trait genes.

Appearance Modeling of Iridescent Feathers with Diverse Nanostructures

Many animals exhibit structural colors, which are often iridescent, meaning that the perceived colors change with illumination conditions and viewing perspectives. Biological iridescence is usually caused by multilayers or other periodic structures in animal tissues, which selectively reflect light of certain wavelengths and often result in a shiny appearance---which almost always comes with spatially varying highlights, thanks to randomness and irregularities in the structures. Previous models for biological iridescence tend to each target one specific structure, and most models only compute large-area averages, overlooking spatial variation in iridescent appearance. In this work, we build appearance models for biological iridescence using bird feathers as our case study, investigating different types of feathers with a variety of structural coloration mechanisms. We propose an approximate wave simulation method that takes advantage of quasi-regular structures while efficiently modeling the effects of natural structural irregularities. We further propose a method to distill our simulation results into distributions of BRDFs, generated using noise functions, that preserve relevant statistical properties of the simulated BRDFs. This allows us to model the spatially varying, glittery appearance commonly seen on feathers. Our BRDFs are practical and efficient, and we present renderings of multiple types of iridescent feathers with comparisons to photographic images.

Synthesis and Coloring Mechanism of Metallic Glaze in R2O-RO-Al2O3-SiO2-P2O5 System

Synthesis and Coloring Mechanism of Metallic Glaze in R2O-RO-Al2O3-SiO2-P2O5 System

The mechanistic origin of amber pigmentation of Perithemis tenera (Say, 1840) wings (Odonata: Libellulidae) and its function in conspecific signalling

Animal coloration serves various signaling and non-signaling functions. In damselflies and dragonflies (Odonata), such colors may not only play photoprotective and/or thermoregulatory roles but also serve as visual signals during courtship and/or agonistic interactions. Here, we analyzed the coloration of Perithemis tenera wings, a potential secondary sexual ornament, applying spectrophotometry and visual modeling to gain a deeper understanding of their color mechanisms and functions. The amber coloration of the P. tenera wings results from the interaction of light with both the melanized chitin matrix and possibly ommochrome pigments. Additionally, by fitting the absorbance curve of P. tenera wings to the extinction coefficient of different melanins, we deduced that pheomelanin is likely the pigment embedded in the wing’s chitinous matrix. The amber coloration of P. tenera wings stands out against their natural habitat, making it detectable by conspecifics. Finding multiple pigments in the P. tenera wings not only enhances our understanding of the functional roles of pigmentation in Odonata but also offer broader insights into how structural and pigment-based colorations evolve as multifunctional traits.

A point mutation in the zinc-finger transcription factor CqLOL1 controls the green flesh color in chieh-qua (Benincasa hispida Cogn. var. Chieh-qua How).

Flesh color is an essential trait in chieh-qua (Benincasa hispida Cogn. var. Chieh-qua How); however, the inheritance and molecular basis of green flesh trait remain unclear. In the present study, two F2 populations, derived from 1742 (white flesh) × FJ3211 (green flesh) and J16 (white flesh) × FJ5 (green flesh), were used to identify the green flesh (Cqgf) locus. Genetic analysis revealed that the presence of green flesh was a quantitative trait that closely followed a normal distribution. Combining the results from QTL mapping and BSA-seq analysis, the Cqgf locus was preliminarily determined to be located on chromosome 05 and was narrowed down to a 2.55-Mb interval by linkage analysis. A large J16 × FJ5 F2 population comprising 3,180 individuals was subsequently used to screen the recombinants, and the Cqgf locus was fine-mapped to a region of 329.70 kb that harbors six genes. One of the candidate genes, Bch05G003700, the zinc-finger transcription factor LOL1 (lsd one like 1 protein; CqLOL1), was the strongest candidate gene for the Cqgf locus according to sequence variation and expression analysis. Additionally, a point mutation (A > C) in CqLOL1 resulted in the substitution of threonine (T) with proline (P) in the amino acid sequence, showing a complete relationship linked with flesh color in a panel of 45 germplasms. The study suggests that CqLOL1 promotes the accumulation of chlorophyll content in chieh-qua and lead to green flesh. Our findings establish a theoretical and technical foundation for breeding different flesh color lines and elucidating the underlying mechanisms of flesh color in chieh-qua.

Mining and expression analysis of color related genes in Bougainvillea glabra bracts based on transcriptome sequencing.

Bract coloration is one of the key ornamental traits in Bougainvillea, yet research has predominantly focused on phenotypic color traits and pigment composition, with limited understanding of the molecular mechanisms underlying color formation. This gap hinders the improvement and innovation in bract coloration. To elucidate the regulatory mechanisms of bract coloration in Bougainvillea and to enhance the utilization of its germplasm resources, this study employed the Illumina Novaseq 6000 sequencing platform to conduct transcriptomic sequencing on 21 samples of bracts exhibiting seven distinct phenotypes. Comparative analysis against Nr, Pfam, EggNOG, GO, and KEGG databases annotated 90,279 unigenes. The highest annotation rates were achieved with the Nr (40.13%), GO (30.44%), and EggNOG (25.64%) databases. Among the species annotated, Beta vulgaris (20.08%) and Chenopodium quinoa (14.58%) shared the highest homology with Bougainvillea bract transcriptomes. WGCNA analysis identified 12 positively correlated tissue-specific modules, of which 2 are related to bract color formation. By comparing transcriptome data and genes within these specific modules against the KEGG database, a total of 321 unigenes associated with bract color formation in Bougainvillea were discovered. Among these, 220 unigenes are involved in anthocyanin synthesis, 43 unigenes are involved in betalain synthesis, 23 unigenes are annotated as Chlorophyll a-b binding protein genes, and 35 unigenes participate in carotenoid synthesis. Quantitative real-time PCR (qRT-PCR) validation of 16 differentially expressed genes (DEGs) including PAL2, CHS1, ANS, BZ1, 6GT, CDOPA5GT, ANR, CHS2, and DOPA, revealed significant expression differences among magenta, yellow, white, and cherry-colored bracts, suggesting their potential as candidate genes for bract color development. This study not only enriches the transcriptomic data of Bougainvillea but also identifies genes associated with bract coloration, providing a valuable theoretical basis for future gene cloning, genetic engineering, and breeding efforts in Bougainvillea.

Transcriptome Analysis Revealed the Anabolic Regulation of Chlorophyll and Carotenoids in Curcuma alismatifolia Bracts.

Curcuma alismatifolia is an attractive ornamental plant in the ginger family. Its bracts come in a variety of colors and are commonly used as cut flowers, potted plants, and landscaping. To investigate the regulation of bract pigmentation in C. alismatifolia, we examined the pigment levels of chlorophyll and carotenoids in the pure color part (PC) and variegated part (VA) of three C. alismatifolia varieties, i.e., "Siam TM Sitrone," "Chiang Mai Pink," and "Snow White." To mine the color mechanisms of the pure color and variegated parts of the bract, we conducted RNA-seq analysis on C. alismatifolia. We identified a total of 89,975 unigenes, and there were 3584 differentially expressed genes identified post-screening. Furthermore, 1858 DEGs were annotated in the GO database and 681 in the KEGG database. We pinpointed key genes responsible for the diverse bract colors in C. alismatifolia, including ZEP for carotenoid synthesis and GAGA2 in the chlorophyll synthesis pathway. This study provides valuable insights into understanding the pigmentation mechanism of bracts in C. alismatifolia and the breeding process.

The CoNb2O6 pigments for brilliant-blue ceramic decoration at high temperatures over 1273 K

To date, brilliant-blue pigments that can maintain outstanding stability in a corrosive environment over 1273 K are still very desirable in the ceramic industry. We systematically investigated the structural, optical, colorimetric and thermal properties of a novel type of CoNb2O6 pigments, which have the 6-fold coordinated Co2+ as chromophores and high-valent Nb5+ as the mainstay factor for structural stabilization. Effective coloring contribution from different visible-light regions, the coloration mechanism and thermal stability of the pigments applied in glaze at 1273–1473 K are revealed for the first time. The Co2+ cation at the distorted [CoO6] octahedra generates the brilliant blue hue, which can maintain the absolute blueness values, b*, at 30–44 even after glaze calcination at 1273–1423 K. The superb thermal performance in a harsh environment of the CoNb2O6 pigments significantly outperforms the classic CoAl2O4 blue, thereby exhibiting attractive prospects for high-end blue-sky–hued decoration for ceramics.

Two-dimensional code marking and coloration mechanism on titanium alloy surfaces via laser gas nitriding

In this study, a nanosecond laser marking machine was employed to nitride the surface of a Ti-6Al-4V alloy in a nitrogen-rich environment. Consequently, a crack-free and uniform nitriding layer was successfully achieved. Furthermore, a 2D code with enhanced contrast was imprinted on the sample, and subsequently, a durability test was conducted to assess its performance. The impacts of laser power (ranging from 9 to 11 W), scanning speed (17 to 23 mm/s), and line spacing (20 to 40 µm) on the surface morphology, thickness, and color alteration of the nitride layer were systematically investigated through experimental analysis. Utilizing a spectrophotometer, scanning electron microscope, optical microscope, energy dispersive spectroscopy instrument, and other advanced equipment, we further delved into the underlying mechanism of surface color change during laser gas nitriding of a Ti-6Al-4V alloy. Results indicate that an increase in laser power and a decrease in line spacing and scanning speed lead to the generation of higher energy densities on the material surface, intensifying ablation and causing the formation of more molten material. Consequently, this results in the development of more complex surface structures, thicker nitride layers, and lower reflectance. The surface microstructure of the nitride layer exhibits similarities and variations, and the thickness of the nitride layer differs, leading to distinct light absorption and reflection properties on its surface. Consequently, the nitride-layer surfaces prepared under varying laser parameters exhibit diverse contrasts.

A circuit motif for color in the human foveal retina

The neural pathways that start human color vision begin in the complex synaptic network of the foveal retina where signals originating in long (L), middle (M), and short (S) wavelength-sensitive cone photoreceptor types are compared through antagonistic interactions, referred to as opponency. In nonhuman primates, two cone opponent pathways are well established: an L vs. M cone circuit linked to the midget ganglion cell type, often called the red-green pathway, and an S vs. L + M cone circuit linked to the small bistratified ganglion cell type, often called the blue-yellow pathway. These pathways have been taken to correspond in human vision to cardinal directions in a trichromatic color space, providing the parallel inputs to higher-level color processing. Yet linking cone opponency in the nonhuman primate retina to color mechanisms in human vision has proven particularly difficult. Here, we apply connectomic reconstruction to the human foveal retina to trace parallel excitatory synaptic outputs from the S-ON (or "blue-cone") bipolar cell to the small bistratified cell and two additional ganglion cell types: a large bistratified ganglion cell and a subpopulation of ON-midget ganglion cells, whose synaptic connections suggest a significant and unique role in color vision. These two ganglion cell types are postsynaptic to both S-ON and L vs. M opponent midget bipolar cells and thus define excitatory pathways in the foveal retina that merge the cardinal red-green and blue-yellow circuits, with the potential for trichromatic cone opponency at the first stage of human vision.

Study on the Metabolic Basis of the Color Formation of Two Color-Presenting Types of Jujube Fruits.

Jujube is a plant of the genus Ziziphus in the family Rhamnaceae; its fruit has high nutritional value, and it is rich in polyphenols, flavonoids, and other secondary metabolites. The color of its peel is an important indicator for evaluating the appearance of the fruit. However, the mechanism of the difference in color presentation between the seedling offspring of the 'Red Fruit' (TLHH) and the 'Green Fruit' (TLHL) of the fresh jujube cultivar 'Tailihong' is not clear. Therefore, this study used targeted metabolomics techniques to accurately and quantitatively analyze the metabolic pathways of carotenoid and anthocyanin metabolites during the ripening process of two color-presenting types of jujube fruits. Through the analysis of the dynamic changes in the pigment content of the jujube peel, it was found that 30 DAP (days after pollination), 80 DAP, and 110 DAP were the key periods for the development of the color of the peel of 'TLHL' and 'TLHH' jujube and that the substances responsible for the main differences were chlorophyll, carotenoids, and anthocyanins. Furthermore, we used an LC-MS/MS metabolic analysis to compare the differences in the carotenoids and anthocyanin metabolites between the two color-presenting types of jujube peels at the key periods of 30 DAP, 80 DAP, and 110 DAP. We detected 32 carotene metabolites and 75 anthocyanin metabolites, respectively, among which lutein had the highest content of carotenoids; it reached the maximum value (93.05 µg/g) and was higher than that of 'TLHH' (74.14 µg/g) at 30 DAP of 'TLHL'. Both showed a decreasing trend with fruit ripening. The anthocyanin with the highest content was cyanidin-3-O-(tartaryl)rhamnoside-5-O-glucoside, which reached the maximum value (258.32 µg/g) at 30 DAP of 'TLHH' and was 51.6 times that of 'TLHL'; similarly, both showed a decreasing trend with fruit ripening. These results elucidate the main metabolites of carotenoids and anthocyanins in the two types of jujube peel and their accumulation characteristics, suggesting that the key metabolites of the difference in color between 'TLHL' and 'TLHH' jujube fruits were lutein and cyanidin-3-O-(tartaryl)rhamnoside-5-O-glucoside, increasing the understanding of the color mechanism of jujube peel and providing a reference for targeted genetic breeding of jujube peel color.

The pseudo-type response regulator gene Clsc regulates rind stripe coloration in watermelon1

The color and pattern of watermelon's rind are crucial external traits that directly affect consumer preferences. Watermelons with stripes having a stronger color than the background rind are ideal for studying plant stripes, while there is still limited knowledge about the genetic mechanisms underlying stripe coloration due to the lack of germplasm resources. In this study, we focused on a watermelon germplasm with colorless stripes, and genetic analysis revealed that the trait is controlled by a single recessive gene. The gene Clsc (Citrullus lanatus stripe coloration), which is responsible for the colorless stripe, was confined into a 147.6 kb region on chromosome 9 by linkage analysis in a large F2 mapping population. Further analysis revealed that the Cla97C09G175170 gene, encoding the APRR2 transcription factor, plays a crucial role in determining watermelon's colorless stripe phenotype and was deduced to be related to chlorophyll and chloroplast development. Based on the physiology experiment results, it can be inferred that Cla97C09G175170 may significantly influence chloroplast development and chlorophyll synthesis in watermelon. The results of this study will be helpful for better understanding the molecular mechanism of stripe coloration in watermelon and for the development of marker-assisted selection (MAS) for new watermelon cultivars.

Transitions between colour mechanisms affect speciation dynamics and range distributions of birds.

Several ecogeographical 'rules' have been proposed to explain colour variation at broad spatial and phylogenetic scales but these rarely consider whether colours are based on pigments or structural colours. However, mechanism can have profound effects on the function and evolution of colours. Here, we combine geographic information, climate data and colour mechanism at broad phylogenetic (9,409 species) and spatial scales (global) to determine how transitions between pigmentary and structural colours influence speciation dynamics and range distributions in birds. Among structurally coloured species, we find that rapid dispersal into tropical regions drove the accumulation of iridescent species, whereas the build-up of non-iridescent species in the tropics was driven by a combination of dispersal and faster in situ evolution in the tropics. These results could be explained by pleiotropic links between colouration and dispersal behaviour or ecological factors influencing colonization success. These data elucidate geographic patterns of colouration at a global scale and provide testable hypotheses for future work on birds and other animals with structural colours.

Intermediate filaments spatially organize intracellular nanostructures to produce the bright structural blue of ribbontail stingrays across ontogeny.

In animals, pigments but also nanostructures determine skin coloration, and many shades are produced by combining both mechanisms. Recently, we discovered a new mechanism for blue coloration in the ribbontail stingray Taeniura lymma, a species with electric blue spots on its yellow-brown skin. Here, we characterize finescale differences in cell composition and architecture distinguishing blue from non-blue regions, the first description of elasmobranch chromatophores and the nanostructures responsible for the stingray's novel structural blue, contrasting with other known mechanisms for making nature's rarest color. In blue regions, the upper dermis comprised a layer of chromatophore units -iridophores and melanophores entwined in compact clusters framed by collagen bundles- this structural stability perhaps the root of the skin color's robustness. Stingray iridophores were notably different from other vertebrate light-reflecting cells in having numerous fingerlike processes, which surrounded nearby melanophores like fists clenching a black stone. Iridophores contained spherical iridosomes enclosing guanine nanocrystals, suspended in a 3D quasi-order, linked by a cytoskeleton of intermediate filaments. We argue that intermediate filaments form a structural scaffold with a distinct optical role, providing the iridosome spacing critical to produce the blue color. In contrast, black-pigmented melanosomes within melanophores showed space-efficient packing, consistent with their hypothesized role as broadband-absorbers for enhancing blue color saturation. The chromatophore layer's ultrastructure was similar in juvenile and adult animals, indicating that skin color and perhaps its ecological role are likely consistent through ontogeny. In non-blue areas, iridophores were replaced by pale cells, resembling iridophores in some morphological and nanoscale features, but lacking guanine crystals, suggesting that the cell types arise from a common progenitor cell. The particular cellular associations and structural interactions we demonstrate in stingray skin suggest that pigment cells induce differentiation in the progenitor cells of iridophores, and that some features driving color production may be shared with bony fishes, although the lineages diverged hundreds of millions of years ago and the iridophores themselves differ drastically.

Gemological Characteristics of Blue-Violet Cordierite

Cordierite is a violet-blue gem mineral primarily composed of magnesium aluminum silicate. This study employed three samples of Mg-cordierite and conducted tests on their gemological characteristics, spectroscopic features, and chemical composition using Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, ultraviolet spectrophotometry, X-ray photoelectron spectroscopy (XPS), and electron microprobe. The study also explored and analyzed the polychroism and coloration mechanisms of the samples. The results indicate that the lattice vibrations of the Mg-cordierite samples differ along the directions parallel to the a, b, and c crystallographic axes, leading to certain variations in spectral characteristics among these directions. The article provides experimental evidence for the reasons for the polychroism of cordierite in different crystal axes, which is of great significance in the quality evaluation of cordierite.

Color Genesis and Chromatography of Yellow Silicified Corals

Color plays a vital role in revealing the formation environment and metasomatic processes of silicified coral. This study investigated the color mechanism and colorimetric characteristics of yellow silicified coral from the aspects of gemology and colorimetry. A Mako G-507C industrial camera, Raman spectroscopy, UV-Vis, EDXRF, and XRD were used for the 16 samples in this study. The results showed that the yellow color of the silicified coral was produced by Fe3+ and influenced by its degree of crystallization. The Raman peaks of all silicified corals were consistent with the standard spectral group peaks of α-quartz, where the yellow part was inferred to be goethite. The peaks at 545 and 505 nm, with a secondary peak near 435 nm in the UV-vis first-order derivative spectrum, were consistent with the presence of hematite and goethite, respectively. The band positions of the second-order derivative spectrum were shown to belong to one single-electron leap 6A1 → (4E;4A1) and one electron pair leap (6A1 +6A1) → (4T1 +4T1). The chroma and lightness were mainly affected by Fe3+. By analyzing the correlation between the Fe content and the characteristic peaks, it was found that an increase in the Fe content led to a red shift in the peak position of the main characteristic peaks, as well as an increase in the hight of the corresponding peaks in the UV-visible first-order derivative spectra. In silicified corals, an increasing crystallinity index is correlated with a decreasing phase proportion of moganite, decreasing Fe content in the bulk, and low chroma.