Gems, or jewels, are mineral crystals often prized for their visual appearance and use as jewelry. They may also include rocks, such as jade, or materials, such as pearls, that originate from organic processes. After being cut, some gems, such as the Cullinan Diamond, were and continue to be used by royalty to adorn crowns and other regalia. Query for famous gemstones with unusual rarity, size or beauty using Wolfram|Alpha. Explore gemstones such as diamonds, opals, aquamarines, rubies, sapphires, emeralds, pearls, topazes and many others.