In a Blue Post from Tseric we learn that:
The exact jewels used in Jewelcrafting have not been finalized, but we plan on using existing gems and creating new ones. Obviously, we are going to avoid any gluts in the market by not announcing them, so hoard at your own risk. ;)
The prospecting skill of Jewelcrafting will operate similarly to smelting, in that you will use the skill to extract gems instead of making bars. While mining is a complimentary profession for this, there are other methods of gathering gems, such as through drops or from other miners(Auction House).
You may want to also check out my older Jewelcrafting Notes.
I have personally found mining to be a good money making skill set so based on this kind of information I can't wait to make my Jewelcrafter/Miner.
Update 10/4/06: I found a post with a description of some BC Jewelcrafting information. I'm not sure how credible it is but here is an exceprt I pulled from it. This could be a list of gems that we see today that might also later be useful in jewelcrafting.
Cut Azerothian Diamond