Geochemical sampling is the systematic collection of geological media—including rock, soil, regolith, stream sediment, water, vegetation, or gas—from a defined area or geological section for chemical analysis, with the objective of characterizing elemental distributions, identifying anomalies, and guiding exploration or environmental assessment programs. In bauxite, gold, iron ore, and diamond mining, geochemical sampling represents one of the most cost-effective early-stage exploration tools available, capable of rapidly screening large areas of prospective terrain at relatively low cost per sample.
The choice of sample medium is governed by the target commodity, local geological setting, regolith maturity, climate, and the nature of the anticipated geochemical dispersion processes. Stream sediment sampling is particularly effective in rugged, actively eroded terrains for detecting catchment-scale anomalies, allowing rapid reconnaissance of large areas. Soil sampling at consistent depth intervals is used to define local anomalies for follow-up drilling in areas of residual or transported overburden. Rock chip sampling of outcrop and float material provides direct mineralogical and geochemical information on source lithologies.
In gold exploration, various sample media are employed depending on the depth of the regolith profile and the nature of gold dispersion. Shallow-oxidized profiles may yield excellent soil or lag sampling results, while deep lateritic weathering profiles may require calcrete, termitaria, or deeper auger sampling to access geochemically meaningful material above the primary bedrock.
In bauxite exploration, sampling of laterite profiles at regular depth intervals using auger or blade rigs provides critical data on Al2O3, SiO2, Fe2O3, TiO2, and moisture content variations required for resource classification and refinery feed quality prediction.
In iron ore exploration, sampling of outcropping banded iron formation (BIF) and associated lithologies by rock chip and channel sampling, combined with systematic soil sampling, characterizes Fe, SiO2, Al2O3, and P distributions guiding drill program design.
In diamond exploration, geochemical sampling of stream sediments and soils for pathfinder elements (Cr, Ni, Mg, Ba, CO2) and indicator minerals (garnets, ilmenite, chromite, olivine, clinopyroxene) is used to vector toward kimberlite source bodies.
Sample collection, handling, labeling, chain of custody documentation, and submission procedures must be standardized and rigorously documented to maintain data integrity and support independent auditing in compliance with international reporting standards such as the JORC Code or NI 43-101.