Iolite – A Gemstone Used in Ancient Navigation
A stupendous stone in my opinion! Its colours range from yellowish grey all the way through to the most magnificent deep blues and violet and that is the colour which particularly mesmerizes me. It is often confused with sapphires and tanzanites. It is plentiful and relatively inexpensive but do not write off its high gemstone quality.
It is found in Switzerland, Germany, Scandinavia, the USA, Sri Lanka, India and Australia as well as many African states. It is also called cordierite.
Iolite comes from the Greek “ios” meaning violet. It was also called diochroite another Greek word which means “two coloured” stone.
On the Moh’s scale used for measuring hardness with diamond being the highest at 10 Iolite comes in at 7-7.5 which means it is about mid range for your usual high quality gemstones. That is significant as it will chip and scratch but will also stand up to normal wear and tear. It seems that it is one of the few stones that is not treated or enhanced. For reference, something like ninety percent of all rubies are heat treated and many other stones such as topaz are irradiated.
The Vikings knew about as it was found in Scandinavia. They knew a secret about iolite which may have changed the course of history. They used it as a navigation tool. By looking through the crystal they could see the direction of the sun on overcast days. This was a function of its pleochroism which means that it changes colour when you look at it from different angles. To understand that better imagine that you can hold it and look at a magnificent deep blue and just by turning it around the colour stars to disappear until you cannot see any colour at all! This is pleochroism and iolite has pronounced pleochroism.
It is a cutters’ nightmare. Well, at least it is not an easy stone to cut and get the most from even though it can be cut into the standard facet cuts such as emerald, marquise, trillion and can also be made into beautiful cabochons.
As the carat size increases iolite generally gets darker and less attractive. The smaller stones are often the most attractive. The lighter blues and greys are less expensive with the richer the blue colour being the more expensive. It is not a birthstone and as a significant gemstone perhaps iolite’s time has not come yet but it is getting more and more popular every day so expect to see it become very popular in coming years. I heartily recommend it to you.
A yellow gold ring with diamonds and a central iolite is simply adorable.