Fair warning: this is what I did; you won't be able to replicate it and you probably won't want to! =) I did have fun, and I did convert a couple of screw-on earrings (that once belonged to my great-grandmother) and a butterfly pin (that belonged to my mother when she was a girl) into pieces of jewelry that I want to wear. Both were given to me as gifts; I don't endorse stealing jewelry from relatives for your own projects!
This is the earring I started with (larger than life). It's partner was missing too many rhinestones and got tossed.
I snapped the back off the earring by hand, although hindsight reveals that maybe my jeweler's saw would have been a better idea. The largest rhinestone popped out in the process. Enter the superglue! Easily fixed. =) (If this whole thing seems like a very irreverent way to treat your great-grandmother's jewelry, I kind of agree. It seems that it should bother me, but it doesn't. If I had any precious heirlooms of course I would preserve them as they are!)
I sanded the broken area smooth. Then with more superglue, I attached a closed jump ring to the back of the jewel. The rest was really simple. I attached a second jump ring and strung a chain through it.
As for the butterfly, it got wet (that's an understatement) in a house flood many years ago. It had never had any discoloration before that, but when I got it back after that event, it looked like this, and hasn't changed since.
Well, until I started messing with it this week, that is. I went online (red flags should start waving right here) hoping someone would say that there was some way to magically clean costume jewelry. I got a few ideas, but neither I nor my mom were sure what kind of metal it was or what the, uh, black stuff was- tarnishing, corrosion? (I actually took a metalworking class in college last year; my professor would be so disappointed in me right now). Some people said toothpaste, some people said baking soda mixed in water, some said vinegar (which I do know gets rid of tarnishing- metal arts student trying to redeem herself here!). Some said to use one of the above and scrub the jewelry with a baby soft toothbrush to get dirt out of the little crevices.
So what did I do? Well, all of the above. Let's sum it up by saying, for my particular case, the toothbrush was not a good idea, and the others were ineffective. A lot of the black stuff did come off, thanks to the toothbrush- along with most of the golden finish (plated, painted, I'm still not sure). I still like it, though, and here's what I made of it:
I bought a gold chain at the craft store and cut it to add the larger, oval-shaped jump rings.
From the back. I didn't want to break the pin for my mom's sake (plus I might want to convert it to something else someday- an ornament on a cuff bracelet maybe?), so I used the pin to hold it to the chain. The beads are just spacers to keep the butterfly from sliding around.
And a bonus: This is another of my great-grandmother's earrings, which I also broke off and superglued to a ring base from the craft store. Would fit right in at Forever 21 in the year 2013, don't you think?