Iolite derives its name from the Greek word 'io', meaning violet flower. It is distinctive because of its strong pleochroism .. hence the name dichroite. Depending on the angle from which it is viewed, a stone can vary from bluish-purple to a wan grey-yellow. Sometimes iolite is also known as 'water sapphire' because a clear stone can resemble a slightly violet sapphire.
Iolite is somewhat brittle and is often cut into stepped rectangles. Its strong pleochroism makes orientation an important factor in determining the best way to cut the stone. Iolite is an inexpensive gemstone but as with almost every other gemstone, large clean sizes are rare and much more valuable. The best iolites come from Sri Lanka, Madagascar, and Burma. Iolite has enjoyed a recent resurgence in popularity due to its affordability and similarity to tanzanite and sapphire at a much lower price.
The largest iolite crystal ever found weighed more than 24,000 carats, and was discovered in Wyoming, USA.