Characteristics of Iolite:

Chemical Name: Magnesium, iron aluminosilicate

Formula: (Mg,Fe) ₂Al ₄(Si ₅AlO ₁₈)

Colors: Blue

Structure: Orthorhombic

Hardness: 7-7.5

Specific Gravity: 2.6

Refractive Index: 1.53-1.55

Lustre: Vitreous to greasy

Streak: White

Locations: Sri Lanka, Canada, Myanmar, Madagascar

What is Iolite? 

Gem-quality blue cordierite is known as Iolite, derived from a Greek word meaning “violet”, a reference to its color. As a gemstone, it is particularly noted for its pleochroism, appearing intense blue in one direction, yellowish-grey or blue in another, and almost colorless as the stone is turned in the third direction. It is almost always faceted, and cutters need to take careful note of the orientation of the stone to obtain the best color. Another informal name applied to Iolite is “water sapphire”, again because of its color.