Aloha, One of the best and oldest for MAC would be FormZ. It is used
alot for architecture but is very suitable for Jewelry models. Check
it out at www.formz.com . If you want to see some output from FormZ,
check out, www.familyjeweler.com. Steven Pollack is the owner and at
one time did training for jewelry applications. There are a few
others or you could always run programs ported to windows, using
Virtual PC, like Rhino 3D. I hope that is of help. If I can be of
assistance, feel free to contact me.