Sapphire and Ruby gemstones are both part of the corundum family of gemstones. Ruby is corundum material occurring in various shades of red. Sapphire is corundum material of nearly any other color including but not limited to blue, yellow, purple and green.
It is a little known and understood fact that the large majority of jewelry-quality sapphire and ruby gemstones are actually heat treated to improve their color. This is a relatively harmless procedure which results in increased clarity and improved color. Sapphire and ruby gemstones of desirable color that have not been heat treated are extremely rare and can command prices as high as $100,000 per carat or more.
When these sapphires and rubies come up for sale, they are almost always presented with certification from an independent gem grading institution such as the AGTA or Gueblin. Certification from one of these institutions provides information regarding the origin of the gemstone, and also notes any indication of treatment the stone may have been subjected to. Though it is very rare, heat treated sapphires and rubies of top quality can command prices very close to those of certified untreated sapphires and rubies.