Iolite gets its name from the Greek word for violet, and like that flower, it’s cool shades range from light to dark blue and violet
It’s a transparent and translucent gem that is strongly pleochroic. From some angles, blue Iolite can actually appear colorless. Other pleochroic colors include gray, violet, or yellow. This optical property allows the gem to act as a strong light polarizing filter, a feature that Viking navigators- on overcast days, used to view the sun through a thin piece of Iolite.