milling (grinding)

https://doi.org/10.1351/goldbook.M03928
The mechanical reduction of the particle size of a sample by attribution (friction), impact or cutting. The required particle size of a sample is related to the size of the
test portion
and the number of particles required to ensure homogeneity among test portions. The reduction in particle size may sometimes result in particles of different hardness and density, which produces inhomogeneity during the preparation of the
test sample
or during the withdrawal of the
test portion
.
Source:
PAC, 1990, 62, 1193. (Nomenclature for sampling in analytical chemistry (Recommendations 1990)) on page 1205 [Terms] [Paper]