Peculiarities about the Sampling of Precious Metals

Theoretical and especially practical problems generated by the sampling of materials containing precious metals have been given enormous attention by many specialists for a long time. It is not by chance that D. W. Brunton, whose contribution constitutes the best precursor to Pierre Gy’s theory of sampling, was working in a gold mine in Colorado at the end of the nineteenth century. Nevertheless, solutions to the sampling of precious metals in general are still unsatisfactory: sometimes propositions are too theoretical and useless for the engineer, and sometimes they are too simplistic and based on empirical observations without solid foundations. In the material presented in this chapter there are still a number of necessary approximations. We will keep these approximations in mind to make sure that they are always valid. A special effort is made in presenting an easy text illustrated by simple practical examples. This makes it possible to quickly calculate the variance of the Fundamental Sampling Error involved during the sampling of precious metals. The objective is to find out, with no ambiguity, if a sample should weigh 30g, 3kg, or 3 tons! This chapter is also an introduction to the intriguing subject of sampling of trace constituents which was already the very important objective of Part V in this book. Peculiarities about the sampling of precious metals can be divided into three categories: