||Violet blue. Light blue – grey blue
Cordierite (Mg, Fe)2Al4Si5O18
7 - 7.5
1.54 - 1.58
2.58 - 2.66
||Not known to be enhanced
Madagascar, Sri Lanka, Myanmar and India
|Warnings for Care
||Fusible – low melting point
Iolites are know by a number of names, the primary name probably comes from the Greek word "ios", which means violet. Cordierite a name applied to both the gem and non-gem variety is derived from the French mineralogist, Cordier. Water Sapphire while once a common name comes from its similarity to paler examples of Sapphire found in Sri Lanka. Viking Compass comes from the stories that Viking sailors allegedly used Iolite mined from Scandinavian deposits as a polarizing filter to find the sun, and assist in navigation on cloudy days or when the sun was below the horizon.
Pleochroism (the ability of a stone to display more than one colour at a time) is very pronounced in Iolite. With the stone actually being trichroic, that is three different color shades being visible in the stone, depending on its orientation. In short depending on the viewing angle, Iolite will display violet blue, yellow gray or a light blue, which require consideration when the rough is selected for cutting
Iolite is usually a purplish / violet blue when cut to enhance its best attributes. The most pleasing color is a pale violet blue that is unlike other gemstones, sitting somewhere between the colour of Sapphire and Tanzanite.
While the stone is hard (7-7.5 on the Moh's scale) it does exhibit imperfect cleavage and therefore care should be exercised in the jewellery manufacturing process.
Iolite - What Causes the Colour
Iolite is another gemstone where the chemical composition rather than trace elements in the crystal lattice are the causal agent of the colour. This Magnesium, Aluminium Silicate is typically blue, violet or brownish depending upon how it has been cut, or the orientation the rough crystal is viewed from. A perfect cube of Iolite would therefore exhibit each colour separately when viewed from the x, y and z-axis respectively. The best color is a pale-medium violet blue that is unlike other gemstones, sitting somewhere between a pale sapphire and a violet Tanzanite. This property led the stone for a time to called "water sapphire" , a name that is now all but obsolete.
Iolite has in recent years seen resurgence in popularity on the back of Tanzanite sales. Exceptional piece come very close to the AAA colour of Tanzanite, and with diminishing quantities of this material being available, Iolite is sure to show price improvements in the future. Iolite is also often sold as an alternative to Sapphire.
The best color is an intense highly saturated violet blue colour.
Iolite show no real difference in colour when viewed under either natural or artificial light. The Pleochroic nature of the stone is exhibited well under either light source.
While clarity plays a second string to colour in the value of an Iolite, major inclusions can mask the beauty of the stone and lower its value. This being particularly the case in large stones. The inclusions are often only visible when the stone is viewed from a certain angle and often have the appearance of rain falling within the stone.
While the pleochroic nature of Iolite does present some complications for a cutter, this is not a problem in the purchase of cut stones. Iolite lends itself well to most cuts, with possible the only limitation being when a stone presents with a deep belly or pavilion. When choosing a cut therefore cognisance should be given to the depth of the stone which should not be to great so as to over darken the finished gem.
Iolite deposits are relatively abundant worldwide, being located in Sri Lanka, India, Myanmar, Australia, Namibia, Brazil, Tanzania, Madagascar, Canada and the USA.
Iolite Common Treatments
There is no known treatment to enhance iolite.
Important & Famous Iolite
No know important or famous examples are currently in existence.
Iolite - The Legend
The sagas of the great Norse explorers tell of a magic stone used to navigate their way possibly to the New World centuries before Columbus. This Viking compass was Iolite used because of its ability to determine the direction of the sun on overcast days.
Shaman believe the stone to have the power to open the way to enlightenment, and clear physic vision
Precious Semi-Precious Gemstones