Geochemical Prospecting

Prospectors with some vision and adequate resources prefer geochemical testing of soils and rocks to the loaming technique. Geochemical sampling can identify and locate deposits with poor surface signatures, such as, when gold particles are present in insufficient quantities or coarseness to show up in a gold pan or concentrator. Geochemical prospecting is carried out to locate hidden ore bodies that are without visible surface indications or to define the location, distribution and size of a known deposit. With this type of prospecting, samples are collected and sent to a lab where they are analyzed for gold and elements associated with gold (pathfinders, particularly As). This type of prospecting can identify a variety of deposits- quartz reef and lode, supergene, hydrothermal replacement etc. Soil sampling is done to locate and analyze the distribution of alluvial and eluvial deposits or locate anomalies that overlie hidden ore bodies. Geochemical sampling of outcrops can be done to determine their gold content. Soil sampling or stream sediment sampling can be carried out to analyze gold or pathfinder elements. For detailed evaluation of prospects, contour maps can be drawn to show the distribution of elements. These may show the distribution of alluvial and eluvial deposits or the location of anomalies, indicating the presence of an orebody (where elements are most concentrated): for example, a reef.

Geochemical sampling permits accurate estimation of the grades and reserves of a gold deposit. For some deposits containing microscopic gold (some shear related, hydrothermal replacement, quartz reef and stockworks deposits) geochemical analysis is the only method able to identify them.