Iolite Color – Blue, Purple, Gray
Discovered in 1813, this stone has many names. Iolite is the term for the jewel quality type of stone called cordierite, named after the geologist Louis Cordier. The gemstone name comes from the Greek word for “violet.” The jewel is also known as “water sapphire.”
Despite being nicknamed for sapphires, the two stones are very different. While corundum is made solely out of aluminum and oxygen, cordierite is a silicate made with magnesium, aluminum and iron.
While cordierite comes in many colors including grey, yellow and brown, iolite is best known for its violet blue, though the hue may change depending on the angle its viewed from. Cutters try to shape the jewel so that it has as much blue as table-up as possible.
On occasion, iolite features inclusions that create optical phenomena. Among these are long hollow tubes within the jewel, which may be oriented and cut to create a cat’s eye effect. Other times, enough metallic platelets are trapped inside the crystal to create aventurescence not unlike aventurine or sunstone. Depending of the type of flecks, they may give the iolite a reddish tinge.
Iolite, also known as cordierite, was formally discovered in 1813 by the French scientist Louis Cordier. The stone’s mineralogical name is in honor of the geologist, while its gemological term derives from the Greek word for violet. Centuries before Cordier, vikings were said to use slices of the jewel to filter out strong sunlight as they navigated the seas.
Today, iolite is favored for its deep blue-purple hues. Cutters must take great care in shaping the stone, as it changes from saturated violet to colorless depending on how it’s angled. Iolite is often transparent, making it well suited to faceted cuts. The jewel tends to be eye clean, though it sometimes contains inclusions that provides cat’s eyes or aventurescence.