Is this diamond, moissanite or cubic zirconia?

Diamond!! I’ve never seen a cubic zirconia in such a gorgeous setting

Honey bun, only a trained gemologist can give you the answer you seek, which is NOT advice in families and relationships. Go to a jeweler.

Take it to a jeweler and get it appraised.

Honestly, it could be a diamond - but it just looks like any ordinary CZ, moissy, white topaz or sapphire to me. Nothing really special about it. If it is a diamond, it just looks like a waste of money in such an ordinary setting. 

no one cares. bring it to a jeweler. or ask the dude yourself. 

I would think that’s a real diamond

No one here can tell from a mere picture. Take it to a jewelry store, where they have people trained in gemology.

A large, reputable store is the type you want.

That is absolutely stunning and personally i wouldn’t mind getting a cubic zirconia as my engagement ring but i know some people do, it looks like a diamond but can’t tell without a tester