iolite
Also known as water sapphire and Vikings' compass, (because of it's ability to determine the direction of the sun on overcast days) Iolite, is a transparent, violet-blue, light blue, or yellow-gray mineral. A pleochroic stone, Iolite will show many colors in a single stone.
Iolite is a popular and interesting gemstone. It has a pretty violet blue color that is unlike other gemstones, although it has been compared to a light blue sapphire. It is for this reason that it is sometimes known as "water sapphire".Although the color is attractive and popular it is not extremely rare and is therefore quite affordable, making Iolite jewelry more and more popular in recent times. While an Iolite necklace or Iolite earrings are probably the best way to showcase this gem stones' unique color, Iolite rings are also possible as it is a durable stone with a hardness of 7-7.5 on the Mohs scale.
Pleochroism is very pronounced in Iolite and is seen as three different color shades in the same stone. In viewing an Iolite, the colors violet blue, yellow gray and a light blue can be seen.
It is very important to look at an iolite from several directions before you purchase because the stone will present very different colors from different angles. If cut properly the stone will show its best blue color through the top or table of the stone. But viewed from another angle the stone may appear colorless.
Most of the Iolite available today comes from Sri Lanka, India, Madagascar and Burma.