Pretty pretty shiny shiny!
This is Garnet's necklace, from Final Fantasy IX.
It was a custom order, and is made from: paperclay, resin putty, the crystal piece, oil paint, metal jewelry hook, metal chain and latch set.
More complicated than one might expect, but I think it turned out well. It's pretty solid too, so no worries about breaking it while wearing it around.
Want one or something like it? Check out my cosplay prop website here: [link]