Wear blue topaz only if you wish to be clear-sighted: legend has it that it dispels all enchantment and helps to improve eyesight as well! The ancient Greeks believed that it had the power to increase strength and make its wearer invisible in times of emergency. Blue Topaz was also said to change color in the presence of poisoned food or drink. Its mystical curative powers waxed and waned with the phases of the moon: it was said to cure insomnia, asthma, and hemorrhages.