That\'s a very ambitious project to try and I really don\'t know what to suggest for the best results. You could look to Chrispy\'s article on painting gems, but what ever it\'s going to be a long exercise to get the whole thing to look right.
If you want to do the whole thing in a quick and easy manner I\'d suggest following GW\'s pattern for Eldar Gemstones, but that has it\'s drawbacks in that it always looks to be illuminated from above.
Good luck with this anyhow!