This transparent violet-blue variety of cordierite owes its name to the Greek ion, meaning violet, and lithos, meaning stone. It has an unusual optical property known as pleochroism, meaning that it takes on different colours when viewed from different angles. Thus the same stone can display shades of sapphire blue, blue-violet, yellowish grey, clear and light blue as it is tilted.
Did you know?
- Iolite has sometimes been referred to as ‘water sapphire’, and also ‘Vikings’ compass’, as Viking sailors used thin pieces of the stone as as a polarising filter to determine the position of the sun, even on overcast days, allowing them to navigate safely.
- Iolite is mined in India, Sri Lanka, Brazil, Mozambique and Zimbabwe. The Vikings probably mined iolite from deposits in Norway and Greenland.
- Iolite jewellery is sometimes given to celebrate a 21st wedding anniversary.