What about them? Diamonds are diamonds, moissanite is close but not the same and very rare naturally only having been found in meteorites really. They make it synthetically though it's still fairly costly I would rather it than a diamond in all honesty.
Emeralds, brittle, too much so in fact to be good in most jewelry. Amazing stones, included by nature and rare in larger sizes.
Everything is more rare than diamonds however diamonds are SOOO hard they make for wonderful rings. Large, very clean diamonds are in fact very rare but diamonds in general not really.
I suspect you are just trying to boost the count, but tell me about peridot, one of my favorites. I like the spring/grassy green of it.