Finding Gold With Magnets

You've probably seen news reports about archaeologists who use planes or boats to tow a large magnet and "map" a site. Question: Would the magnetic field pick up silver and gold? Would the gold's anti-magnetic properties create a disturbance in the field that would reveal its whereabouts?
- Joel (age 52)
Oxnard, Calif., USA

The diamagnetism of gold is so weak that I don't see how it could be picked up against the variable magnetic background of all sorts of other things in the ground. However, if an ac electromagnet were used, the the fields from the eddy currents stirred up in any veins of gold or silver might be detected. That's the basic principle of metal detectors. It can be used to detect metallic elements that are present in metallic form, as opposed to say iron, which is typically present as nearly insulating oxides.

Mike W.

(published on 11/09/2012)