My girlfriend is intent on looking for a toy from way back in the early-mid 90's and will not rest until she has found out what it is. I know what she's talking about, but I can't remember the name of it, myself.
Basically, they were rocks. And you dropped them in water. The rock dissolved and revealed a plastic jewel inside. It came with different fixtures that you could put these "jewels" into and wear as bracelets, rings, necklaces, etc.
If anyone knows what this is, please let me know so I can surprise her!