I tried doing this, but the only gold piece of jewelry I have other than my wedding band turned out to be plated crap. Nuts.
If selling gold, it is best to find an honest, reputable local jeweler that buys gold. We are fortunate to have a good one 5 minutes down the road. He'll tell you if the jewelry in question is worth more in it's weight in gold vs as a piece of jewelry or vice versa. And when my wife bought a gold chain to shorten, he actually gave her cash from the small bits that were no longer needed. Awesome.
My wife goes around with a jeweler loop and hits up the local thrift shops and antique stores and buys crap looking gold bracelets and such for a few bucks, then sells them for $20-$40. Others do it too though, so it's not a huge money maker. More of a hobby.
She did have a set of gold cuflinks she bought 10 years ago for $5 at a thrift shop. Sold them a few weeks ago for their weight in gold (they were broken) for $350.
That'd be a gun right there, but that isn't her thing. Oh well.