“Yakutniproalmaz” Institute (Mirnyy, Russia):

Makarskiy I. V., Head of Laboratory, Candidate of Chemical Sciences, e-mail: MakarskiyIV@alrosa.ru

This article is devoted to the development of the method of instrumental quality control of the deep thermochemical purification of diamonds, using the «Lambda 950» spectrophotometer, produced by the Perkin Elmer company. Such a method is based on the registration of the changings of spectrometric characteristics of crystals, connected with the typical contaminations of diamonds. The removal of these contaminations is possible by the thermochemical methods. As far as various types of contaminations lead to the crystals color shift, the color model L*a*b* is used for the definition of the calculation of diamonds color characteristics, by the absorption spectrums. Using this model, the numerical color characteristics and their variation range, which characterize the type of particular contamination and color of diamond, were defined by the absorption spectrums of crystals. The definition of the color of crystals by the limit value of L*a*b*, along with the belonging of crystals to one or another contamination, are being held with the usage of the specially developed algorithm, which was realized, using the Microsoft Office Exsel program package. This algorithm makes it possible to classify the diamonds by 19 color groups, corresponding to various types of contaminations and colors of diamond, according to the SITY classifier. This algorithm is adaptable. In case of need, it makes it possible to scale up the systematic groups. The discussion about the purification rate of all inspection lots is possible, due to the numerical values of the content of crystals with ironing and bitumen contaminations, obtained before and after  the thermochemical processing of the check sample of diamonds.

This research work was held with the financial support of the Ministry of Education and Science of Russian Federation, within the project No. 2010-218-01-001 “Creation of complex innovation environmentally safe technology of extraction and processing of diamondiferous ores in the Far North”, which is being held with the participation of North-Eastern Federal University named after M. K. Ammosov and “ALROSA” JSC.

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