The collection and analysis of the silt, sand, mud, clay in a stream or river bed, either dry or wet, is a common gold exploration method.
Stream sediment sampling is usually employed as an early stage exploration tool to cover large areas relatively quickly in the hope of identifying smaller areas of interest to be followed up with prospecting and more detailed (and costly) sampling techniques.
The idea behind this method is that the fine material found in stream beds has been eroded from the surrounding rock, and so represents a mixture of all the land occurring upstream from that point. The gold explorer hopes that if a gold deposit exists somewhere above the sampling point, a small but detectable amount of gold will be found in the sediment sample.
A stream sediment sampling program may take one sample for every 10 square kilometres of land area. The total area sampled this way may cover 100’s or 1000’s of square kilometres. When all the samples are taken and analysed for gold or trace elements, the results will be looked at together to determine the background and anomalous (higher than usual) levels of gold. The sampling points with anomalous results, especially if clustered together, indicate an area that may have a gold deposit somewhere upstream of them.
