Report describes a research project undertaken for North Broken Hill Ltd, Exploration Div., to ascertain the suitability of the mercury-halo method of geochemical prospecting for concealed base metal deposits, with particular reference to exploration ground which NBH holds in the Murray Valley of South Australia. Studies were made using the following three approaches: a) laboratory experiments on the behaviour of mercury in soils; b) analysis of soils for the area in question, and consideration of the implications of the results; and c) examination of the available literature to consider whether the method was useful, and whether it could be applied universally. A secondary objective was to scan the literature for other potential remote sensing geochemical prospecting techniques.