Secondary halos, which correspond to deposition of transported minerals during periods of erosion and weathering. Primary halos are directly associated with primary mineral deposits . Pathfinder elements identify the type of primary mineral deposit. Arsenic traces, for example, identify gold and silver veins. Radon vapor emissions identify uranium deposits.
Secondary halos allow the identification of potential regions for detailed analysis.
A variety of geochemical surveys are discussed as means of locating and isolating the primary and secondary halos. Stream sediment surveys are used for reconnaissance exploration. Water surveys involve instrumental water analysis of dissolved minerals in water basins. Soil and vegetation surveys are used to pin-point the exact location of of a potential ore deposit. Bedrock surveys and vapor surveys are used to identify primary points of dispersion and leakage of minerals.