The notes on Jewlcrafting sould give you a idea, and anybody who played D2, and espeicaly LoD, should recoginise blizzard "Reusing" a idea. A jewlcrafter will most likely use bars and gems(Gasp) to make rings, amulets, as well as ... jewls. They have announced "Sockets" and thats what you keep a jewl in. Nobody is sure how this will stack with enchaments, but a ideal woudl be that they stack!!! so for example you have a epic jewl that was made with jewlcrafting, using piles of arcane crystals and huge emeralds, you put it in you socketed soward that has crusader(or bigger,as god knows what comes for enchantments)enchant, now you put you gem in the soward(Permenetnly) and boom it gets a bonus form the gem(someing like Attack haste, or extra damamge)
repeat for other applictable stuff, like plate and mail(maybe cloth and leather, but who knows)