That ring would have made my day if I found it and that is really great of you to have returned it. The neat thing about that ring is that I graduated the same year she did. I got a class ring as well and lost it, but not in same sense. I sold my mine so I could go meet a girl with whom it didn't work out with. I tried to recover it later on, but the pawn shop had already melted it. The sad part is it over an ounce of gold, cost only $500 back then, but would be worth a good bit more now.
But back to talking metal detecting. Here in North Georgia where I live we have lots of small beaches or beaches that are always being resanded (not sure if that is right word I'm looking for. These beaches are located on Lake Sidney Lanier and most only produce newer finds. Besides change I do find fake Jewelry sometimes, but that isn't always bad. Sometimes the fake/costume Jewelry has fake metal but, the stones are real. No I've never found Jewelry with diamonds, not from these beaches that is. But sometimes I find Jewelry with Opals, a single pearl and birth stones. I do keep those pieces. My best finds are a couple of late 60's silver dimes I found. I'm sure they were probably dropped by kids playing and coins were probably given to them by parents or grandparents.
Here is a little bit of back ground info on Lake Lanier if you didn't already know. Lake Lanier is a man made lake and was once part of Chestatee River and is still fed by the Chestatee River. It was constructed in the 1950's and was finished in 1956 ... So your not going too find much on the beaches since they are mordantly new and get combed all the time by parks and rec and The Army Corps of Engineers. However there are rumors of CSA treasure being hid in some of the caves and wells once part of homes near where the lake is now. There's also rumors of treasure under the lake, but you know how rumors are, but there a slight of truth to some of them. However there are a few stores of kids finding gold and silver coins dated to around time of the Civil war. I try researching these things all the time, most of the rumors just come to a dead end since not much was published in the local papers.
Sorry for going on for so long, but I figure you or someone might find this information entertaining or even useful.