This paper can be considered a case history in which geology, geophysics, and more particularly geohydrology and geochemistry, when applied to the problem of origin of a vitriol lake, led to discovery of a copper prospect. After a review of various postulated origins for the vitriol lake and previous interpretation of the local structure, new evidence based on borehole and geophysical data demonstrated that the structure consists of two anticlines and two fault systems. Study of the geohydrologic conditions as related to the fault systems and the geochemistry of their water indicate the lake is the result of mineralized water whose circulation is controlled by the fault zone. Source of the copper in these waters may be some hidden copper deposit in a direction away from the known ore bodies. -- J. Lemish.