Some guy who had a girlfriend at the time asked me if I wanted children, what kind of engagement ring I wanted, what color wedding ring I want (platinum, gold or white gold), told him it was hard to answer since I was not in that situation
talking about this with other people, he saw how the cost of diamonds has gone down and wondered why I don’t want a diamond engagement ring (I said I was not interested cuz I always wants something pretty-my birthstone)
If thats what you want then go for the opal, but they are a softer stone and will chip/crack/scratch more easily. It might not hold up to day to day wear depending on your profession.