Introduction. Desired component mass fraction distributions in point samples at preparation plants are asymmetric, and it is due to the natural heterogeneity of ores. The theory of mass fractions distribution asymmetry in samples. The theory is based on the lump sampling of point samples. Mass fraction distributions here consist of two different-sized fractions: valuable mineral and rock. These distributions are always asymmetric. Lump dispersion for asymmetric distributions depends on the mass fraction of the valuable mineral for both released grains and aggregates. Mass fraction distribution in point samples withpoor product mass fraction is described by the Poisson formula. Materials and methods of research. Mass fraction distribution correspondence to the Poisson formula was experimentally confirmed based on an artificial rock mass represented by quartz grit with colored markers. Point samples of different mass were collected from the rock mass. Experimental estimates. The distributions obtained experimentally correspond to the distributions calculated by the Poisson formula. The paper introduces a method for experimental determination of valuable mineral average grain size and ore texture index. These values were determined for asbestos ore to exemplify the method proposed. Results discussion. Sampling standards do not consider the asymmetry of mass fraction distributions in point samples. At preparation plants the asymmetry manifests itself in hurricane samples, positive product imbalance, and divergence of double weights analysis results, that exceed the acceptable limits. The asymmetry of components mass fraction distributions in concentrates should be taken into account in sampling standards and methods, as well as at preparation plants in general.
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