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Gemspedia >> Gems >> Introduction to Gemstones >> Iolite



Also known as water sapphire

Major Sources

India, Madagascar & Sri Lanka

Colors Found

Violet blue, light blue or yellow gray


Cordierite: (Mg, Fe)2Al4Si5O18


7 to 7.5

Refractive Index

1.54–1.58; Biaxial (+ or –)

Specific Gravity


Crystal System




The name iolite comes from the Greek word ios, which means violet. Iolite is a transparent, violet blue, light blue or yellow grey gemstone. A pleochroic gem (different colors are displayed when the gemstone is viewed from different angles), iolite will show many colors in a single piece.


Legends and lore

According to ancient Scandinavian sagas, Norse navigators used thin pieces of iolite (their magical ‘sunstone’) as the world’s first polarizing filter. Looking through an iolite lens, they could determine the position of the sun on overcast days and navigate their boats safely. Hence iolite is also known as the Viking’s compass or Viking’s stone. The story of the Viking compass triggered the curiosity of a 10 year-old boy who just happened to be the son of the Chief Navigator of the Scandinavian Airline System, Jorgen Jensen. The “sunstone” described in Norse lore sounded similar to the twilight compass used by his father at higher latitudes where a magnetic compass is unreliable. His father’s twilight compass was equipped with a polarizing filter that enables a navigator to locate the sun, even when it is behind the clouds, by light polarized by the atmosphere.


Intrigued by his son’s observation, Jensen passed it onto Danish archaeologist Thorkild Ramskau, who immediately recognized its scientific implications. Collecting minerals found in Scandinavia whose molecules are aligned similarly to the crystals in a polarizing filter, Ramskau put iolite (the gem variety of the mineral cordierite) to the test. Accompanying navigator Jorgen Jensen on a flight to Greenland, Ramskau kept track of the sun with a piece of iolite while Jensen used the twilight compass. Incredibly, his observations were accurate to within 2.5 degrees of the sun’s true position.

Known as the gemstone of clear vision, when worn as an amulet, iolite was believed to have the power to guide lost sailors to the brilliance of the sun, allowing them to safely find their way home.


Just the facts

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 light blue sapphires. It is for this reason that it is sometimes known as water sapphire.

While an iolite necklace or iolite earrings are probably the best ways to showcase this gem’s unique color, iolite rings are also desirable, as it is a durable gem well suited to everyday wear.


Pleochroism (different colors displayed when viewed from different angles) is very pronounced in iolite and is seen as three different color shades in the same gem. When viewing iolite, the colors violet blue, yellow grey and a light blue can be seen. When correctly faceted, iolite will show its best violet blue color through the top or table of the gem, but when viewed from another angle the gem may display other colors.


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