Is it really not possible to trace gold? I was under the impression that for much of the gold out there you could use the "footprint" of contaminations in the g

Is it really not possible to trace gold? I was under the impression that for much of the gold out there you could use the "footprint" of contaminations in the gold to infer the age (since mining) and procedence to a certain degree. Of course, if you melt it in a top-notch facility, they'd probably be able to heat out the contaminants (or remove them chemically?), but people trading in stolen or otherwise "hot" gold probably don't have access to such facilities.