In the context of mineral assaying, "salting" refers to the act of intentionally or accidentally altering the composition of a mineral sample to misrepresent its value, often by adding valuable minerals (enriching) or diluting it (impoverishing). This practice can skew assay results, leading to incorrect estimations of a deposit’s worth. Decimating (option 1) means reducing drastically, sniffling (option 3) is not a mining term, and sludging (option 4) relates to drilling mud, none of which fit the definition. Thus, the correct answer is Salting.