Diamond engagement rings are usually tricky. It's an old school answer -- it's often a law school answer. But the general rule is that it's considered a gift and so it's usually not given back.
Sean Sullivan is a family lawyer practicing in the Elmhurst, Illinois area at the law offices of Laura M Urbik Kern, specializing in child custody and dissolution in divorce. Visit his website, www.laurakern.com, and Divorce Magazine profile.