Diamonds
Diamonds are simultaneously the rarest and most common gem of all gems. While it is the hardest gem, making it common, it is also the only gem with a hardness of ten, making it very rare. There can only be one diamond of each color living at a time. Diamonds are very highly respected, but are also envied for their status and face the risk of being killed by jealous gemigons. They have no supernatural significance (such as special powers) besides their strength, beauty, and rarity, though they do have the same odds of acquiring special abilities as any other gemigon does.