Other resources

• Ruby and Sapphire: from red to deep blue
  It's hard to imagine that a mineral with a name as mundane as corundum yields gems as exquisite as the ruby and sapphire, or even that these two stones, so different in color and mystique, are actually the same mineral family. These are among the richest-colored of all gemstones with a romance and history as colorful as they are. Rubies are actually rarer than sapphires, and only red corundums are called rubies.
  Read more: Ruby and Sapphire
• Treated diamonds: Change the color and improve the quality of your diamonds
  Treated diamonds can have improved clarity, improved color and even be completely coated to improve it's overall appearance. If you decide to purchase a treated diamond, just be sure you inform the jeweler when you bring your diamond in for cleaning, as they may need to use different chemicals to clean it and maintain it's treatment.
  Read more: Treated diamonds