What is channel sampling?

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

This is the most frequently used and accepted method of sampling in most exploration projects and operating mines. The method consists of marking an outline and cutting uniform grooves into the rock about 100 mm wide and 20 mm deep across the exposed mineral body, usually spaced across the strike, collecting all the fragments and dust from the channel, and combining together to constitute one sample.

While marking the channel outline, it must be taken into consideration that channel outline, as far as possible, should be along the direction of maximum variability. Various tools ranging from a hammer and moil to a pneumatic chisel can be used to cut channel sample.

Before attempting to collect a sample, the exposed rock surface must be cleaned thoroughly, with a wire brush, water, or chipping a fresh surface. The cross section of channel being cut should be kept uniform so that the sample cut becomes representative.

The samples can be chiseled out and collected carefully on a clean sheet of canvas placed directly below the channel. The sides and floor of the channel should be smooth and uniform to avoid any overcutting/undercutting that may overrepresent/underrepresent. The channels may be divided into 1-2 m sections or their multiples in case of massive or more homogeneous ore bodies or intersection of 50 cm in case of more heterogeneous distributions. It is a good practice to divide larger samples into smaller intervals according to the structure, change in rock types, or differences in rock hardness or strengths.

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