E-trec-virginia is right, there's no way around the sad fact that gold and aluminum share the same conductive ranges, on a size-per-size basis.
And aluminum and gold also come in infinate sizes, densities, karots, shapes, alloys, etc.... Foil wads can be compact and "crisp", or they can be elongated and thin and "chattery" and so forth.
I have heard persons give the advice like Jeff in PA, that they think there is a "tone" or "softness" or "boldness" difference between aluminum and gold. But all you need to do, to put an end to this notion, is invite those persons to a blighted inner city park, or junky beach like yours, and turn them loose. See how much gold they get, while leaving even a portion of aluminium behind
The reason why it's easy to fall for the feeling that "gold sounds different", is because of a subliminal subconscious trick our mind plays on us. It works like this: When you FINALLY find gold, you say to yourself "that sounded different than all the aluminum I just dug", and you sincerely want to believe that ....... therefore ........ if I could only learn those tone differences! But what's really at play there, is nothing more than subconscious selective memory at work. Each time we all stop to dig something, we're saying "this sounds different". But when we pull up the umpteenth aluminum globule foil wad, we then say to ourselves "yeah, it *did* sound kinda junky, now that I think of it". But when you FINALLY find gold, you think "aha! I *knew* it sounded different". Sort of the same way we sometimes get fooled into thinking our dreams come true. You dream hundreds of dreams per night, none of which ever come true. But the the one time your dream comes true (like the song you dreamed about, is the one that turns on your radio alarm clock that morning), you remember just that one dream, and think "aha, I'm psychic". It's the same thing at play for those who think "gold sounds different". Well sure, a selected gold ring (or chain or earing or whatever) will give one sound, and an aluminum wad or tab will give another sound, on a test-by-test basis. But SO TOO will each gold ring sound different from each other as well. And so too will each aluminum item/glob/wad sound different from each other too.
If anyone persists that gold gives a different sound (even if they only have a 20% accuracy), quickly turn them loose on your beach, and see what their ratios are