In 2006, the city of San Francisco went to install an artificial turf soccer field @ one of their old parks . Park dated to the 1880s. The tractors needed to peel off the top 6 or 8" to prepare for the incoming synthetic turf. You can imagine it was "Christmas come early" for those of us md'rs who were on top of this

Old coins everywhere

(story got in Western and Eastern Treasure mag.)
HOWEVER: By the 3rd day, the tractors were folding back in some of the surface modern soil. I guess to get the right grade, depth, compaction, etc.... But since it was all just jumbled up soil, we still had the liberty of "digging all" . Since holes was not an issue in a demolition site.
For an entire week I kept every single target I found. I had buckets for the junk, another pile for clad, and of course my old coins in a 3rd pile. My intention was to do a study of the ratios, #'s, etc... At the end of the week, I DID INDEED have a few gold rings, a gold charm, a gold pocket watch part, etc... But the junk ratio was something on the order of 150+ to each gold item I had found. This was a park nestled in a blighted bad area of SF. So you see: it would simply have been unfeasible, had it not been for the demolition, to have gone into a turfed park with the notion of angling for gold rings . My time would have been better spent simply going to the beach, if gold rings were my agenda.
Oh, and of 10 or 12 hunters in on that event: No gold coins were found. Also: the soil was KILLING nickels. They came out horrible orange/brown cruddy and you could barely read dates on buffalos & V's. One hunter, on one of the nights, wised up and started passing low conductors .
That's a no-no in demolition hunting , RIGHT ?? And he ended up with the most barbers and seateds of any hunter that night . Considering that most all the silver was better S mints (go figure, we're right in SF), you can see
he actually had the wisest strategy. Eh?
Also be aware: A $5 gold (the most common) is actually not a "low" conductor. It reads at about the beefy square tab (not the flimsy square tab range). Ie.: about 49 to 50-ish on the old Whites scale (Eagle, XLT, etc...). So you could actually pass foil, round tabs, etc... and STILL not miss a $5 gold Needless to say, $10 and $20 read even higher than that.
Thus ... sometimes, like in blackjack in Las Vegas, you are wiser to "hold" if you have 20 in your hand. Despite that the next card *might* be a one card. Sometimes you can't have the best of both worlds.