Toby, I have to chuckle when I read someone's "recipe" for finding gold jewelry, is to turn down the disc. and dig all the foil, tabs, can slaw, etc...

Well yes, of course it's no secret that gold and aluminum share the same conductivity. But that's only a small part of the recipe of how to find gold jewelry. It's 99% more a function of WHERE you are hunting, that makes a difference. I can think of blighted urban inner city parks, where you can easily dig 1000 foil and tabs before you will ever dig a single gold ring. It's simply not worth it. Your time is MUCH BETTER spent going to where the gold ring ratios are better, to begin with.
Namely: swimming beaches (either fresh water bodies, if you're inland, or the beach, if you're near the coast). Swimming and sand is a natural for jewelry losses: people lathering up in suntan lotion [read: "slippery"], then jumping into the cooler waters [read: "shrinks fingers], in a horizontal frolicking position [read: un-natural body positions], pitching balls and frisbees, and the one I love most: taking their jewelry off for "safe-keeping" and putting in their pocket or shoe or whatever.

The sand is also a hundred times easier and faster to dig in, than trying to strip-mine the turf.
Even pool-side turf (if you're not near any swimming holes/beaches) is better than regular turf ratios. And other types usage: soccer fields, wrestling sand pits, more upscale parks, etc... As opposed to picnic turf (like around picnic tables) where people had all their picnic stuff (tabs, foil, etc...) as they ate. Athletics are a bit better jewelry ratio than eating areas. And swim and suntan type sand areas are better yet. A word of caution: some sandy beaches can also be hellacious, if they are college beer-drinking party areas, where beach bonfires, for example, introduce molten can globs, etc... Sometimes you gotta pick the right beach, just like picking the right land site.