Cause Of Color Research Articles

CORÍNDON NO BRASIL: QUÍMICA, INCLUSÕES, ESPECTROSCOPIA E ASPECTOS GENÉTICOS

Investigation of mineralogical and chemical characteristics of corundum from eleven deposits in Brazil aimed to contribute to the understanding of genesis and to obtain a set of data to be used as a finger print to elucidate provenience of unknown samples. In most deposits corundum is recovered from recent sediments except in two cases where it is found in the host rock. Trace-elements were analyzed by INAA and ICP-OES, solid inclusions by SEM-EDS and absorption spectra were obtained in the range of UV - visible. The most important trace-elements considered in the discussion of cause of color and/or genesis are REE, Th, Ga, Fe, Ti, Cr, W, Sb, La, and Ta. Formation by high-grade metamorphismin aluminous metasedimentary rocks is suggested for corundum from most deposits (Catingal and Lajedinho - BA, Palmeiras, Sapucaia, lndaiá and Caputira - MG) as indicated by geological context, mineral inclusions and/or chemistry. In Peixe (TO), corundum hosted in pegmatite is magmatic. In the secondary deposits of Malacacheta and Campo Belo (MG), Coxim (MS), and Barra Velha (SC) the genesis of corundum is unclear or possibly due to the interaction of metamorphic and metassomatic processes.

Rubi e safiras de Minas Gerais, Brasil

Rubis e safiras de quatro depósitos em Minas Gerais, denominados Sapucaia, Indaiá e Palmeiras, na região de Caratinga-Manhuaçu, e Malacacheta, mais ao norte, foram caracterizados em termos geológicos, gemológicos, químicos e espectroscópicos, com o objetivo de interpretar causas de cor, gênese, bem como analisar o potencial econômico dos depósitos. Resultados de análises químicas e espectroscopia UV-visível mostram que a provável causa da cor azul é transferência de cargas entre Fe2+ e Ti4+, enquanto Cr3+ causa tonalidades violeta e púrpura, efeito alexandrita e fluorescência. A ausência de Ce e La e o teor relativamente mais alto de Ga distinguem as amostras de Malacacheta das demais. Além de sugerir particularidades genéticas, a diferença em termos de elementos-traços, pode ser utilizada como indicador de proveniência das gemas. Inclusões de um polimorfo de Al2SiO5 e indícios de campo sugerem que o coríndon deve ter sido gerado por processos metamórficos regionais, o que expande as possibilidades para a descoberta de novas ocorrências de rubi e safiras nos terrenos de alto grau metamórfico do leste de Minas Gerais.

The Adaptive Significance of Coloration in Mammals

Abstract Coloration is a diagnostic tool for identifying mammals, but inquiry into its function has lain dormant for almost a century. Recently, the topic has been revived and modern phylogenetic methods have been applied to large data sets, allowing researchers to assess, for the first time, the relative importance of three classic hypotheses for the function of coloration in mammals: concealment, communication, and regulation of physiological processes. Camouflage appears to be the single most important evolutionary force in explaining overall coloration in mammals, whereas patches of colored fur are used for intraspecific signaling. Sexual selection is associated with flamboyant ornamentation in a minority of primates and other restricted mammalian taxa, but to a far lesser extent than in birds. Interspecific signaling among mammals includes aposematic coloration, exaggeration of signals to deter pursuit, and lures for misdirecting predatory attack. Physiological causes of coloration, including melanis...

The causes of colour in untreated, heat treated and diffusion treated orange and pinkish-orange sapphires — a review

The causes of colour in untreated, heat treated and diffusion treated orange and pinkish-orange sapphires — a review

Influence of chemical and mineralogical composition on color for commercial talcs

AbstractCommercial talcs are pulverized mineral products with a variable chemical and mineralogic composition, widely used in industry. Although generally white, they have color variations. The aim of this study was to establish relationships between color parameters and the chemical and mineralogic composition of commercial talc samples, in order to investigate the causes of color. Chlorite, dolomite, magnesite, and calcite were the most abundant accessory minerals. Fe, Mn, Ti, and Ni were the most abundant chromophore chemical elements. Factor statistical analysis (89.8% of total variance explained) revealed that the influence of each mineral species on the different color parameters a*, b*, and L* is well defined (the highest loading factors). Chlorite associated with Fe, Mn, Ti, Zr, Cu, Zn, and V, and calcite associated with Zn, Cu, Sr (and, to a lesser degree, Fe, Mn, Ni, and Co) affect the color parameters a* and b* by inducing chromatic variations (greening and yellowing). Dolomite and magnesite associated with Fe, Sr, Ni, Co, V (and, to a lesser extent, Mn and Cu) affect L* by inducing darkening.

The physics and chemistry of color. The fifteen causes of color, second edition

Color Research & ApplicationVolume 27, Issue 5 p. 377-378 Book Review The physics and chemistry of color. The fifteen causes of color, second edition Rhea T. Eskew Jr., Rhea T. Eskew Jr.Search for more papers by this author Rhea T. Eskew Jr., Rhea T. Eskew Jr.Search for more papers by this author First published: 27 August 2002 https://doi.org/10.1002/col.10085Citations: 3AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Citing Literature Volume27, Issue5October 2002Pages 377-378 RelatedInformation

The physics and chemistry of color: the fifteen causes of color

The physics and chemistry of color: the fifteen causes of color

Fibrous nanoinclusions in massive rose quartz: The origin of rose coloration

Pink nanofibers were extracted from rose quartz from 29 different pegmatitic and massive vein localities throughout the world. Their width varied from 0.1 to 0.5 μm. On the basis of optical absorption spectra of the fibers and the initial rose quartz, we conclude that these nanofibrous inclusions are the cause of coloration of massive rose quartz worldwide. These fibers do not occur in the rare, euhedral variety of pink quartz. Redox and heating experiments showed that the pink color of the fibers is due to Fe-Ti intervalence charge transfer that produces an optical absorption band at 500 nm. Based on the XRD patterns and characteristics of pleochroism, the best match for these inclusions is dumortierite. However, FTIR and Raman spectra consistently did not exactly match the standard dumortierite patterns, suggesting that this fibrous nano-phase may not be dumortierite itself, but rather a closely related material.

The cause of colour of the blue alexandrites from Malacacheta, Minas Gerais, Brazil

The cause of colour of the blue alexandrites from Malacacheta, Minas Gerais, Brazil

The spectroscope and gemmology

Contents in this book include the history and development of spectroscopy; a discussion of the nature of absorption spectra and the absorption spectra of solids and gem minerals; the many uses of the spectroscope and the spectrophotometer, light sources and the causes of colour; absorption in synthetic gemstones; and more. Written for gemologists everywhere and incorporating the latest developments, this is an indispensable textbook for professional and amateur gemologists and students of gemology.

Characterization of a notable historic gem diamond showing the alexandrite effect

A notable historical natural gem diamond showing a color change under different light sources (alexandrite effect) was nondestructively investigated by optical microscopy, an ultraviolet (UV) fluorescence imaging system, FTIR, and other spectroscopic methods. When viewed between crossed polarized filters, the diamond displays a large number of slip planes caused by plastic deformation parallel to {1 1 1} faces. The cause of color of the diamond is directly related to the growth features and to deformation during the post-growth stage. The post-growth slip planes contribute to the brownish color of the diamond, while intrinsic nitrogen-bearing defects, which cause an intense blue fluorescence to ultraviolet radiation, result in a more pink color appearance under daylight.

The diversity and implications of animal structural colours.

Diffraction gratings were believed to be a rare cause of colour in nature. However, surface gratings, which include diffraction gratings and Bragg gratings, appear to occur in many forms within a diversity of animals. Structural colours in general have implications in the study of animal behaviour and evolution.

Russian Synthetic Pink Quartz

Transparent crystals of facet-grade synthetic pink quartz, produced by hydrothermal growth from a fluoride solution and subsequent treatment, have been commercially available since 1994. The characteristic properties that distinguish this material from its natural counterpart are a tabular crystal morphology with two large, well-developed basal faces; color bands parallel to the basal faces and the seed plate; two-phase inclusions adjacent and perpendicular to the seed plate; and an intense broad band around 3420 cm-1 in the infrared spectrum. Color stability and cause of color in synthetic pink quartz are briefly discussed.

Exploration into the cause of urea coloration during its synthesis.

Urea, which is synthesized directly by reacting ammonia and carbon dioxide under high temperature and high pressure, is at times tinged pale yellow when stored for some time. The cause of this coloration has not been clarified. It was observed that carbon dioxide, when compressed during urea synthesis, attained its supercritical state in the compressor. Extraction of a compressor oil with supercritical carbon dioxide was carried out under actual plant operating conditions, and found that the compound extracted was 2, 6-di-tert-butyl-p-cresol (BHT). In addition, it was confirmed that urea containing a small amount of BHT developed coloration when it was exposed to sunlight.

The causes of colour and colour change in caterpillars of the poplar and eyed hawkmoths (Laothoe populi and Smerinthus ocellata)

Caterpillars of the poplar and eyed hawkmoths (Laothoe populi and Smerinthus ocellata respectively) were reared under different conditions in order to determine why final instar caterpillars vary in colour. Poplar hawkmoth caterpillars normally rest on the undersides of leaves. Dull green and redspotted caterpillars are genetically determined polymorphisms. Caterpillars that are not dull green, however, can become white when fed on Populus alba or yellow-green when fed on Salix fragilis. Experiments showed that it is the reflective qualities of the leaves that determines which colour the caterpillar develops: if the young larva sees white then it becomes white, but if it sees green, grey or black then it becomes yellow-green. Young eyed hawkmoth larvae always developed into grey-green final instar caterpillars under our rather poorly-illuminated rearing conditions, but when reared on wild plants in white muslin sleeves they became whitish-green. In this species also it appears that colour of the final instar is determined by the reflectance of the substrate perceived by the young caterpillar.

Biological Action of Colorless and Yellow Solutions of Gold Sodium Thiomalate on Thrombin Activity and the Mixed Lymphocyte Reaction

AbstractGold sodium thiomalate is a pale yellow powder which forms a colorless solution when added to sterile water. The marketed form of gold sodium thiomalate is a pale yellow solution. The yellow color develops as a result of the sterilization process. This study demonstrates that the physical change induced in the drug by the sterilization process has no effect on the action of gold sodium thiomalate on the serine esterase thrombin, nor on the inhibition of the mixed lymphocyte response. Thus it is unlikely that the yellow component is responsible for benefit in rheumatoid arthritis. If the components creating the yellow color cause toxicity, the preparation and/or formulation of the drug should be changed.

Chemistry of postage stamps: Dyes, phosphors, adhesives

Dyes and pigments, the causes of color in dyes and pigments, luminescence in papers and inks, and adhesives.

The fifteen causes of color: The physics and chemistry of color

AbstractThe fifteen causes of color derived from a variety of physical and chemical mechanisms are summarized in five Croups in this article. Vibrations and simple excitations explain the colors of incandescence (e.g., flames), gas excitations (neon tube, aurora), and vibrations and rotations (blue ice and water). Ligand‐field‐effect colors are seen in transition‐metal compounds (turquoise, chrome‐oxide green) and impurities (ruby, emerald). Molecular orbitals explain the colors of organic compounds (indigo, chlorophyll) and charge‐transfer compounds (blue sapphire, lapis lazuli). Energy bands are involved in the colors of metals and alloys (gold, brass), of semiconductors (cadmium yellow, vermillion), doped semiconductors (blue and yellow diamond), and color centers (amethyst, topaz). Geometrical and physical optics are involved in the colors derived from dispersive refraction (rainbow, green flash), scattering(blue sky, blue eyes, red sunset), interference (soap bubbles, iridescent beetles), and diffraction (the corona aureole, opal).

The Varied Causes of Color in Glass

ABSTRACTAll but two of the fifteen physical and chemical mechanisms which are necessary to explain all the varied causes of color apply in one way or another to glass. These fifteen causes of color derive from a variety of physical and chemical mechanisms and are summarized in five groups with concentration on those mechanisms that apply to glass and the related glazes and enamels. Vibrations and simple excitations explain the colors of incandescence (e.g. flames, hot glass), gas excitations (neon tube, aurora), and vibrations and rotations (blue ice, water, glasses based on water). Ligand field effect colors are seen in transition metal compounds (turquoise, chrome oxide green, glasses based on copper sulfate) and impurities (ruby, emerald, many doped glasses). Molecular orbitals explain the colors of organic compounds (indigo, chlorophyll, organic glasses) and charge transfer compounds (blue sapphire, lapis lazuli, “beer-bottle” brown and chromate glasses). Energy bands are involved in the colors of metals and alloys (gold, brass, glassy metals), of semiconductors (cadmium yellow, vermillion, chalcogenide glasses), doped semiconductors (blue and yellow diamond), and color centers (amethyst, topaz, irradiated glass). Geometrical and physical optics are involved in the colors derived from dispersive refraction (rainbow, green flash, glass prism spectrum), scattering (blue sky, blue eyes, red sunset, ruby gold and opal glasses), interference (soap bubbles, iridescent beetles, cracks in glasses, interference filters), and diffraction (the corona aureole, diffraction grating spectrum).

New hole centers in natural quartz

In natural citrines five new hole centers were detected and analyzed by electron paramagnetic resonance. An additional one was observed in rose-colored quartz crystals with radiation defects as the cause of coloration. Characteristic hyperfine patterns due to an adjacent aluminum impurity were resolved in the spectra of three of these centers. Their relations to other hole centers of well-known structure in quartz and fused silica are discussed and possible models for their structures are proposed.