In ancient time, Iolite was used as a navigation tool. By looking through the crystal the direction of the sun on overcast days was seen. This was a function of its pleochroism meaning to change color when you look at it from different angles. To understand this more clearly, imagine that you have an Iolite and its a magnificent deep blue in color and just by turning it around the color starts to disappear until you cannot see any other color at all!
