Iolite – A gemstone that is not just for Vikings!
Iolite is a beautiful blue gemstone that is affordable and durable. Iolite has gone out of fashion, but is a stone worth investigating! The vikings had a use for iolite and I think today it is undervalued for its use in jewellery.
What Should We Know About Iolite?
- Alternate birthstone for September
- 21st anniversary stone
- Also called Dichroite, referring to its strong pleochroism
- Water Sapphire is Iolite (not a sapphire)
- Found as colourless, pale blue, violet, yellow, gray
- Generally free of inclusions that can be seen by the naked eye
- Hardness is good enough for rings (not just earring and pendants)
Is Pleochroism Good or Bad and What causes Pleochroism?
Pleochrosim means that the gemstone is seen as a different colour in different directions. Some gemstones are dichroic (show two different colours or shades) and some are trichroic (show three different colours or shades). The different colours are seen because different wavelengths are absorbed in different amounts depending on the direction that the light travels through these gemstones. Sometimes the different colours can be seen with the naked eye and sometimes a polarizing filter is used to detect the different colours. A good gem cutter (lapidary) is required to cut iolite to obtain a good sized stone with the best deep violet-blue colour “face up” in the finished gem. Iolite has strong pleochroism, this means that the difference in the colours is easily visible in different directions. Iolite is trichroic and usually shows blue, violet and pale yellow depending on the direction.
When we judge coloured gemstones we judge them “face up” (table up) while balancing the stone between our fingers in the palm of our hand. This lets the light be reflected in and out of the stone through the crown (top of the faceted stone). With iolite we want to see the beautiful violet or blue colour “face up”. If we see a yellow stone, then the lapidary has not considered the pleochroism in iolite.
Typically iolite is not treated. It is risky to clean iolite jewelry in an UltraSonic Cleaner, and risky to use a steamer. Warm, soapy water and a soft brush as the best way to clean this gemstone. Iolite is heat sensitive, the stone fuses easily before a jeweller’s torch, abrupt temperature changes could cause fracturing. Chemicals that could attack this gem are acids. A cleavage plane could cause the stone to break. The most common cut to be found is oval or octagonal (rectangular) step cut.
Iolite is often confused with Sapphire and Tanzanite
When the iolite is showing a beautiful blue colour it looks like sapphire, but it is not as hard as sapphire. When Iolite is showing its purple colours it resembles tanzanite, which is also a highly plechroic gemstone. Iolite is more plentiful and less expensive than tanzanite and is now becoming more fashionable in jewellery.
Iolite can be found in Sri Lanka, Brazil, India, Tanzania, Burma, Finland, Madagascar, Namibia, and Norway. The rough is usually just a few carats in size, so to find anything over 3 carats is a rare find.
The Vikings used Iolite as a Polarizing Filter
Iolite Legend – The Vikings
(Join our poll or Scroll Down To The Bottom and leave a comment) – Emerald is winning the poll!
I plan to introduce different gemstones alphabetically. I will start with “A” (Ammolite) and see where it leads me. Leave a comment and let me know if you have a favourite gemstone that starts with the letter “J”. Take the poll! Can you name a reference to a gemstone in a song, movie or book?