Invariably, you will get tricked into going to a gem museum. It is a pain to not really have a choice—your taxi driver, guide, or "friend," will just turn in one. They are actually sort of interesting because they show you how the gems are mined (still by hand), and they also show you a mock mine. Then comes the high pressure sales. Buy something if you like (bargain with them), otherwise don't feel obligated. They are just salesmen, and I personally don't feel like I'm hurting their feelings. You of course will be their first customer of the day, so they will give you great bargains to cast good luck on the rest of their day—B.S.