In the north east, in spring, we’d use magnets to collect iron filings in the street from the snow plows. It was just a thing we’d do, no financial interest. We’d keep our haul in 35mm film canisters (as was the style at the time!)

It's a little more complicated than that - gold is a little bit magnetic, and heat or light can increase this magnetism

So does that mean it's possible to develop a magnetic 'figure-print' for gold?

Magnets only really work for iron.