Iolites are know by a number of names, the primary name probably comes from the Greek word “ios”, which means violet. Cordierite a name applied to both the gem and non-gem variety is derived from the French mineralogist Cordier. Water Sapphire while once a common name comes from its similarity to paler examples of Sapphire found in Sri Lanka. Viking Compass comes from the stories that Viking sailors allegedly used Iolite mined from Scandinavian deposits as a polarizing filter to find the sun, and assist in navigation on cloudy days or when the sun was below the horizon.
Pleochroism (the ability of a stone to display more than one colour at a time) is very pronounced in Iolite. With the stone actually being trichroic, that is three different color shades being visible in the stone, depending on its orientation. In short depending on the viewing angle, Iolite will display violet blue, yellow gray or a light blue, which require consideration when the rough is selected for cutting
Iolite is usually a purplish / violet blue when cut to enhance its best attributes. The most pleasing color is a pale violet blue that is unlike other gemstones, sitting somewhere between the colour of Sapphire and Tanzanite.
While the stone is hard (7-7.5 on the Moh’s scale) it does exhibit imperfect cleavage and therefore care should be exercised in the jewellery manufacturing process.