Valuable Gemstones

People complain about Emerald's sole use being in trading, but I think that makes it more interesting and unique! In fact, I think a variety of new gemstones with varying values and worth could be a cool idea for added depth in trading! Things like Topaz or Rubies or Sapphires could be more or less desirable to Villagers than Emeralds depending on their rarity. Since we see Amethysts coming to the game, why not add a few extra gems? Heck, since I seem to be so enthusiastic about adding new item-specific slots to the inventory, a wallet item/slot which could hold "currency" would be a nifty addition to go along!