@o2l_-5sos isn't moissanit a really good choice when it comes to engagement rings? i mean - they aren't really diamonds, just really close so idk if it would count for you as a "that's not a diamond" stone hahah, but i remember reading it had a really high hardness on the mohs scale. i think zirconia was pretty high as well?
idk what to say about moonstone, it's really pretty (as all gems are), but i think it's good that you're considering something that could stay in almost perfect condition for longer - even if you're a careful person.
Congrats on your engagement, by the way!!! <3