I hope this tutorial will help you! It is particulary for gemstones(not jewels) but you can expand the idea into benefiting from this tut... you can use it for all sorts of glassy ongects and even eyes!
In cace you are wondering where the eyes staring at you above are from - it from my latest picture I am currently making (the 2 rings are from there too. i might make a tut of making jewelry if anyone is interested). It has a lot of gemstones in so i decided why not ,make a tut ?
Please, if you use this tut DO SHOW ME THE RESULT