Iolite Physical Properties

Iolite Physical Properties loose sale price & Iolite Gemstone Information

  • Refractive Index 1.542-1.551

  • Hardness = 7-7.5 (Moh's Scale)

  • Specific Gravity = 2.61

  • Species - Iolite

  • Optic Character - Double Refraction.

  • Phenomena – Rare


The property that made iolite so valuable to the Vikings is extreme pleochroism. Iolite has different colors in different directions in the crystal. A cube cut from iolite will look a violetish blue almost like sapphire from one side, clear as water from the other, and a honey yellow from the top. This property led some people to call iolite "water sapphire" in the past, a name that is now obsolete.

Pleochroism may have been helpful in navigation but it makes things difficult for a gem cutter. If iolite is not cut from exactly the right direction, no matter the shape of the rough, its color will not show to its best advantage.

The name iolite comes from the Greek ios, which means violet. Iolite is usually a purplish blue when cut properly, with a softness to the color that can be quite attractive.