Sampling effects related to the asymmetry of distributions of mass fractions of components in point samples

Numerous evidences of underestimation of the mass fraction during testing according to the requirements of standards for gold, diamond, asbestos, tungsten and other ores, as well as stable positive discrepancies in commodity balances need to be explained. The occurrence of such underestimations is associated with the right–sided asymmetry of the mass fraction distributions in point samples taken from poor products, and the left-sided asymmetry from rich products. It is shown that with a relatively small number of point samples, there is a steady underestimation of the mass fraction when testing poor products and an overestimation when testing rich ones. Such a shift in the results of testing is called a probable systematic error. A probable systematic error occurs both when sampling from both heterogeneous and homogeneous (mixed) tested array. It was found that the relative probable systematic error during testing at copper-zinc processing plants is up to minus 8% for ore and tailings and plus 3% for concentrates. Assay analysis on hangings of 5 g underestimates the mass fraction of gold in comparison with the analysis of hangings weighing 50 g by 7,35—44,34% with a separate compensating overestimation by 89,46%. It is possible to reduce the probable systematic error at processing plants only by switching to high–frequency sampling, and when reducing samples and selecting samples for analysis, by switching to the largest reduced samples and samples by weight.

Kozin V. Z., Komlev A. S. Sampling effects related to the asymmetry of distributions of mass fractions of components in point samples. MIAB. Mining Inf. Anal. Bull. 2022;(11-1):107— 118. [In Russ]. DOI: 10.25018/0236_1493_2022_111_0_107.

Kozin V. Z.¹, Head of the Department of Mineral Processing, Dean of the Faculty of Mining and Mechanics, Dr. Sci. (Eng.), Professor, ORCID ID: 0000-0001-7184-919X, е-mail: gmf.dek@ursmu.ru;
Komlev A. S.¹, Cand. Sci. (Eng.), Senior Researcher, ORCID ID: 0000-0002-2484-2726, е-mail: tails2002@inbox.ru;
¹ Ural State Mining University, Russia, 620144, Yekaterinburg, Kuibyshev str., 30.

Komlev A. S., е-mail: tails2002@inbox.ru.

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