Television and internet ads regularly extol the classic beauty of gold jewelry and dazzling shine of cut gemstones. While we're all familiar with the precious gems — diamonds, sapphires, rubies and emeralds — there are hundreds more semiprecious gemstones, according to the International Gem Society. And sometimes even organic materials that are made into jewelry (like pearls) are considered gemstones.
Many gemstones are crafted into jewelry using gold, a soft, malleable element. Although gold is a relatively rare metal, scientists aren't sure exactly how much of it exists in the world — or how much is left to mine.
