Errors in sampling

This article was written by (Gandhi & Sarkar, 2016)

Sampling is subject to certain limitations due to two types of errors: (1) random and (2) systematic. The random errors tend to cancel out each other, whereas the systematic error accumulates to create gross errors, which are easily recognizable because of their magnitude.

The errors may also accumulate due to four factors: (1) when check samples are taken from the same spot, there would be a natural divergence between the principal sample and the check sample in terms of the grade, which cannot be overcome, (2) errors accumulated due to measurement errors, poor facilities and equipment, and poor eye judgment of the sampler, (3) errors due to mistakes of calculations, misprints, and poor numbering, and (4) limitations of the assay technique itself. In addition, errors may crop up because of intentional or unintentional salting of the sample itself.

All these errors have to be avoided to the maximum extent possible to get a reliable estimate of the orebody. Check sampling and repeated sampling help in avoiding some of the mistakes like salting.

Errors due to several factors may occur in the sampling process and thus affect the result of sampling. These errors can be identified broadly under three categories, viz. (1) human errors; (2) analytical errors; and (3) inherent errors. Of these, human and analytical errors can be reduced to an optimum level, whereas the inherent errors are the ones intrinsic to the type of mineralization. A list of various factors that are responsible for the errors, which should be taken care of, is given in table 1:

Table 1: sampling errors factors

 Reference

Gandhi, S. M., & Sarkar, B. C. (2016). Chapter 9—Sampling and Analysis. In S. M. Gandhi & B. C. Sarkar (Eds.), Essentials of Mineral Exploration and Evaluation (pp. 235–255). Elsevier. https://doi.org/10.1016/B978-0-12-805329-4.00016-8