Abstract: A method and apparatus has been provided to locate a subterranian precious ore and/or sulfide body from which mercury gas is emanating. The apparatus includes an inverted plastic drinking cup from which a mercury-free silver wire is suspended from its end. This is accomplished by inserting the end of the wire into a foam insulation disk located in the bottom of the inverted cup. Alternatively, wire may be attached within a cap of a storage vial. The cap has an adhesive on the outer surface which adheres it to the bottom of the cup, whereupon the vial is removed from the cap to expose the wire. A foil disk is placed on the outside of the bottom of the cup. A plurality of cups are buried in the ground forming a dead air space around the wire, for a period of weeks wherein any mercury-vapor in the ground in the area of the cup is adsorbed by the wire. These cups are arranged in a predetermined array and are subsequently located by means of a metal detector which can detect the metal foil on the cups.