Rare 4.5ct Iolite

In legends, ancient Viking navigators used thin slices of iolite as filters to help locate the sun on cloudy days. Whether or not the tales are true, iolite (mineralogists call it cordierite) can be fashioned into beautiful gems. Strongly pleochroic iolite has been incorrectly called water sapphire, as it can display a blue to violet hue in one direction and pale yellow to colorless in another.

When tanzanite was first discovered, gemologists initially suspected it might be cordierite, a transparent, pleochroic, violet-blue gem known for thousands of years. Today, cordierite (named after geologist Pierre Cordier) is better known by its trade name, iolite, which comes from the Greek word ios, meaning violet.

Iolites strong pleochroism makes the gem tricky to cut for best color. This in turn continues to pose challenges to producers and buyers interested in promoting the attractive yet problematic gem to retailers as an affordable blue-gem alternative.