The boundaries of the region corresponding to kaolin samples from the Zhuravlinyi Log deposit in the MKO L * A * B * colorimetric system are determined. It is shown that a discriminant analysis makes it possible to interpret the color formation processes in kaolin after it has been worked at different temperatures as well as to evaluate the contribution of variables -color coordinates -in the dominant processes in each heat-treatment interval. A procedure is proposed for identifying the latent (hidden) component of the coloring power of iron compounds in the kaolin. Multidimensional gradation of kaolin samples with respect to whiteness and yellowness according to quality categories is performed.The suitability of kaolin as a basic component of a ceramic mix is determined, on the one hand, by the technological properties of the slip and the ceramic mix and, on the other hand, by the properties of the calcined material, including the coloristic characteristics.The main factors affecting the color of kaolin are the following:the total content of iron-containing minerals and iron, bound with organic compounds; the ratio of the silicate (isomorphic impurities in kaolinite or in the form of structure-forming atoms, for example, in hydromica) and nonsilicate iron, represented by iron minerals, including goethite, hematite, pyrite, and others; iron minerals, which can be in the form of micro-inclusions of individual grains or films enveloping particles of clay minerals; the levels of the structural organization of iron-containing minerals: magnetically dilute iron (isomorphic impurities in kaolinite), molecular-cluster (associates, clusters, polymer networks, smaller than 5 nm), superparamagnetic state of iron (5 -10 nm particles), crystalline state of iron minerals (particles larger than 20 nm).The coloristic characteristics of a large number (277) of samples of iron minerals have been analyzed in many works. The effect of these characteristics on the color of clay-containing materials [2, 3] and the dependence of the color of kaolin on the heat-treatment conditions has been studied [4].Iron minerals differ with respect to the color tone (from red hematite to yellow goethite) as well as the brightness (from light-yellow goethite to grey-black iron sulfide). The color of iron minerals depends on the dimensions of the crystals. As hematite crystals increase in size from 0.1 to 1.0 mm, their color changes from red-yellow to purple-red [1]. The same color change occurs with aggregation of hematite crystals. Substitution of Al for Fe has a positive effect on the brightness of hematite. Hematite crystals become darker as they become smaller. The darkening and reddening of goethite particles intensifies as the needles decrease in length from 0.80 to 0.05 mm [2].An important coloristic characteristic of iron minerals is their coloring power. Iron minerals fall into the following sequence with respect to the relative coloring power [1]: hematite p feroxygite > ferrihydrite > goethite.Therefore, iron minerals in kaolin differ not...
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