Iolite

Color:   Medium to dark purplish blue
   
Gem Family:   Iolite is the gem form of the mineral corderite.
   
Source:   Iolite is mined in India, Sri Lanka, Madagascar, Zimbabwe, and Brazil. The Vikings probably mined iolite from deposits in Norway and Greenland.
   
Clarity:   Ranges from no visible inclusions to moderately included.
   
Size Range:   0.5 carat to 3 carats. It is more common to find iolite with beautiful blue below a carat in size: larger sizes are often too dark or show a brown secondary tone.
   
Shapes Available:   Ovals, cushions, trillions, rounds, barions and emerald brilliant cuts are available.
   
Enhancement:   Iolite is not treated: the color is natural, exactly as it is found in the earth.
   
Lore & History:   The name iolite comes from the Greek ios, which means violet. Iolite is usually a purplish blue when cut properly, with a softness to the color that can be quite attractive. When Leif Eriksson and the other legendary Viking explorers ventured far out into the Atlantic Ocean, away from any coastline that could help them determine position, they relied on iolite to help them determine their location. They used thin pieces of iolite as the world's first polarizing filter. Looking through an iolite lens, they could determine the exact position of the sun, and navigate safely to the new world and back.
   
Toughness & Hardness:   Iolite is relatively hard, with a Mohs Hardness of 7 to 7.5, but should be protected from blows.
   
Care & Cleaning:   Clean with mild dish soap: use a toothbrush to scrub behind the stone where dust can collect.
   
Special Characteristics:   The property that made iolite so valuable to the Vikings is extreme pleochroism. Iolite displays different colors in different directions in the crystal. A cube cut from iolite will look a violetish blue almost like sapphire from one side, clear as water from the other, and a honey yellow from the top. This property led some people to call iolite "water sapphire" in the past, a name that is now obsolete. Pleochroism may have been helpful in navigation but it makes things difficult for a gem cutter. If iolite is not cut from exactly the right direction, no matter the shape of the rough, its color will not show to its best advantage, since the blue is mixed with yellow and brown. Fine gems show only the violet-blue colors.