Iolite is a light to intense purplish / blue gem with a hardness of 7 on Mohs scale. Iolite is the gem for 21st anniversaries and a possible alternative to Tanzanite. There is a limited supply in fine quality and large sizes. Iolite is found in Sri Lanka, Brazil, India, Kenya and Madagascar. Iolite is doubly refractive with an RI of 1.537 – 1.551 and displays intense trichroism, the specific gravity of Iolite is 2.58 – 2.66.