>>31458791Point was, the conditions under which diamonds form might be much more rare on Equestria's planet than Earth. Hell, they might not even be diamonds. Also, gemstones all have significantly different conditions in which they form, yet we see different kinds of gems clustered together in the show. Even if they're all the same gemstone but differently colored, they would still have different formation conditions.
Rock autism aside, Rarity's talent is about taking things and making them beautiful, not just sticking rare gems on them. Plus, her cutiemark matches her eyes. Can you imagine rarara with emeralds on her ass? Hideous.
>>31458825Who cares? If she's got a fat ass, everything else is secondary.