Rainbow Moonstone is named for its moon-like glow or chatoyancy, as well as a prismatic quality that differentiates it from other varieties of Moonstone. Moonstone is a Feldspar mineral that was used in Roman jewelry nearly 2,000 years ago. It has also been considered a sacred stone in India throughout its history, believed to have a special significance to those in romantic relationships. It is said to help with Protection and love. Chakra: Crown. Mohs hardness 6-6.5.