My boyfriend and I got engaged a few months ago and one of my friends encouraged me to get my ring insured because it appeared to be pretty expensive. When I had it appraised for the insurance company I found out that it's not a real diamond but instead a cubic zirconia. He has a good just so I don't understand why he wouldn't give me a diamond when proposing. My friends think I should give the ring back and take that as a sign that this isn't meant to be, but I'd like to think that our relationship means more to him than the ring he chose to give me.
I wouldn't assume that your fiance isn't really in love with you or that he doesn't want to marry you just because he gave you a CZ engagement ring, but I would wonder what kind of financial skeletons he has in his closet. Have the two of you discussed debt and credit scores yet? If not, you certainly need to. Once you're married his debts will become your debts and visa versa. He may have a good job but if he's up to his neck in debt he wouldn't be able to afford the ring he really wanted to give you. Have a talk with him and admit you discovered the truth about the ring and then let that open the door to discussing finances. If you're going to have a future with him you need everything laid out on the table. No secrets!