Hi,
uhm... I think it couldn't be such easy stuff. If that way any am RF receiver tuned to that frequency will do the job of locating gold at distance, but it isn't!
I think that (if something exist for real) it's not about a particular "frequency" but maybe some E-field variation around target: that will explain why many lrl are simple e-field detectors... but I simply can't see how they could be useful cause are too false signals addicted (randomic beeps).
Kind regards,
Max