Blue Topaz - the birthstone for December. Blue Topaz is derived from the Sanskrit word "tapas," meaning fire.  This is because Blue Topaz was considered by ancient civilizations to have cooling properties.  Not only was it believed to cool boiling water when thrown into the pot, but to calm hot tempers as well!  This gemstone was credited with many other healing powers, among them the ability to cure insanity, asthma, weak vision and insomnia.  The Blue Topaz was even thought to have magical properties in its ability to make its wearer invisible in a threatening situation.