Color of minerals

To learn more about ionic compounds, visit the Chemistry Web site at chennistrynfic.confi Activity Research the colors of minerals and their chemical formulas. Which elements seem to be in the most colored compounds What are their uses Make a chart to report your findings. 

Determination of the color of mineral oil is used mainly for manufacturing control purposes and is an important quality characteristic. In some cases the color may serve as an indication of the degree of refinement of the material. However, color is not always a reliable guide to product quality and should not be used indiscriminately in product specifications (ASTM D-156, ASTM D-1209, ASTM D-1500, ASTM D-1544, ASTM D-6045, IP 17). 

P. Groth.,45 Q. Rose, and A. Schrauf found chromium in wulfenite. The coloration of minerals by chromium was discussed by W. Hermann, K. Schlossmaoher, and... 

The color of minerals is one of their most fascinating properties and is frequently the first thing that draws attention to the mineral. Color can originate in a number of ways from the presence of a cation or anion that is colored, from the presence of an impurity that is colored, or from a defect in the arrangement of the ions in the solid. The color is always a result of the transition of electtons in the ions or the crystal lattice from one energy level to another. Before we explain this movement of electrons we need to review the nature of light and the electromagnetic spectrum. 

Platonov A (1979) Color of minerals. Naukova Ehimka, Kiev (in Russian)... 

Pedone V, Cercone K, Burrus R (1990) Activators of photoluminescence in calcile evidtaice from high resolution, laser excited luminescence spectrometry. Chem Geol 88 183-190 Platonov A (1979) Color of minerals. Naukova Dumka, Kiev (in Russian)... 

Scandium is apparently much more abundant (the 23rd most) in the sun and certain stars than on earth (the 50th most abundant). It is widely distributed on earth, occurring in very minute quantities in over 800 mineral species. The blue color of beryl (aquamarine variety) is said to be due to scandium. It occurs as a principal component in the rare mineral thortveihte, found in Scandinavia and Malagasy. It is also found in the residues remaining after the extrachon of tungsten from Zinnwald wolframite, and in wiikite and bazzite. 

Slate. Used for hundreds of years, slate comes from different geographical areas and varies in color and weight. Slate (36) is easily spHt to size and shape the most common is 4.76-cm (3/ 16-in.) thick and can weigh 31.71 kg/m (650 lb/100 ft ) or more. Imitation products of mineral fiber and cement stimulate its durabiUty and style. 

The decomposition of dithionite in aqueous solution is accelerated by thiosulfate, polysulfide, and acids. The addition of mineral acid to a dithionite solution produces first a red color which turns yellow on standing subsequentiy, sulfur precipitates and evolution of sulfur dioxide takes place (346). Sodium dithionite is stabilized by sodium polyphosphate, sodium carbonate, and sodium salts of organic acids (347). 

When Cr202 is introduced as an impurity into the a-Al202 lattice, as occurs in the semiprecious mineral mby, the color is red rather than the normal green. This color anomaly is the result of ligand field splitting of the Cr(III) ion (51,52). Chromium (ITT) also colors other minerals (53). 

The advance of sulfur trioxide as sulfating agent largely depended on advances in sulfonation/sulfation reactor development and changes in raw material quality. Undiluted sulfur trioxide cannot be used as a sulfating agent except in special cases where suitable equipment is used because of its violent nature. Sulfur trioxide diluted in an inert gas, usually air, when used in batch processes can cause excessive dehydration and dark-colored products. However, batch processes were used years ago and inert liquid solvents were often suggested or used to moderate the reaction. Inadequate reaction conditions lead to a finished product that can contain dialkyl sulfate, dialkyl ether, isomeric alcohols, and olefins whereas inadequate neutralization conditions can increase the content of the parent alcohol due to hydrolysis of the unstable acid sulfate accompanied by an increase of mineral sulfate. 

Commercial elemental sulfur is usually of bright-yellow color at 20 °C [36]. Pure orthorhombic a-Ss is, however, of greenish-yellow color at 20 °C but totally colorless at 77 K while commercial sulfur often remains pale-yellow at this temperature [59]. The reasons for this different behavior are twofold. Commercial samples are never pure Ss but besides traces of organic impurities they always contain Sy in concentrations of between 0.1 and 0.5% [59]. Sulfur found as a mineral in Nature sometimes also contains Sy but in addition traces of selenium are quite often present (up to 680 ppm Se, probably as SySe molecules) [60]. These minor components influence the color of the samples at ambient and low temperatures in the sense that a more orange-type of yellow ( egg-yellow ) is recognized. 

Care must be exercised in the choice of acid employed in chloramine T — mineral acid reagent since the detection sensitivity and also the color of the fluorescences produced depend to a significant extent on the choice of acid. This is illustrated for the purine derivatives caffeine, theobromine and theophylline in Figure 1 and Table 1. 

The coloration of the chromatogram zones was the same for all three variants of the reagents and did not depend on the nature of the mineral acid used. 

In this paper we will describe and discuss the metal-to-metal charge-transfer transitions as observed in optical spectroscopy. Their spectroscopic properties are of large importance with regard to photoredox processes [1-4], However, these transitions are also responsible for the color of many inorganic compounds and minerals [5, 6], for different types of processes in semiconductors [7], and for the presence or absence of certain luminescence processes [8]. 

Gonzalez-Miret, M. L., Terrab, A., Hernanz, D., Femandez-Recamales, M. A., and Heredia, F. J. (2005). Multivariate correlation between color and mineral composition of honeys and by their botanical origin. /. Agric. Food Chem. 53, 2574-2580. 

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