Iolite
cordierite
Cordierite, transparent and violet-blue, and famous for a story that may well be true: thin slices act as a polarising filter, and there is a serious argument that Norse navigators used it to locate the sun through overcast. It changes colour so dramatically with viewing angle that cutters must orient it precisely or it comes out grey.
Seen · you don't have this one yet
Mineral facts
Hardness
7-7.5 Mohs
Formula
(Mg,Fe)2Al4Si5O18
Family
silicate
Where it comes from
India, Sri Lanka, Madagascar, Tanzania, Brazil, Myanmar, Norway
What it is
Cordierite, transparent and violet-blue, and famous for a story that may well be true: thin slices act as a polarising filter, and there is a serious argument that Norse navigators used it to locate the sun through overcast. It changes colour so dramatically with viewing angle that cutters must orient it precisely or it comes out grey.
What it is confused with
tanzanite, sapphire, amethyst, blue-quartz, sodalite, blue-glass
Strong trichroism is the entire identification: turn the stone and it shifts from violet-blue through smoky grey-yellow to nearly colourless, with the change being dramatic and visible to the naked eye, no other blue stone at this price does that. Colour is a soft inky violet-blue, never the vivid blue of sapphire or the green-blue of aquamarine. Transparent to translucent, vitreous-to-slightly-greasy luster, and it scratches glass readily.
How to tell
Rotate it under a single light. Iolite goes from blue to grey-yellow to almost clear across three axes; tanzanite shifts blue-violet-burgundy but never to colourless-grey, and is softer (6.5). Amethyst shows no such change.
Essentially never treated, another gem sold as-found.
What it means for you
The Moon is at 1° Scorpio today. Iolite is a silicate, 7-7.5 on the Mohs scale, and it is the stone traditionally carried when the problem is proximity rather than intensity.
You know what this one would do for you. You just don't have it.
Iolite for every sign
Aries
Cut it at the wrong angle and it comes out grey.
Turn it and it goes from violet-blue to smoky grey-yellow to almost colourless, depending on which axis you look down. Thin slices act as a polarising filter, and there is a serious argument that Norse sailors used it to find the sun through cloud. Cut it at the wrong angle and it comes out grey.
Taurus
Cut on the wrong axis it comes out grey.
Cordierite, and thin slices of it act as a polarising filter, which is the basis of a serious argument that Norse sailors used it to find the sun through cloud. Rotate it and it goes blue, then smoky yellow, then almost clear. Cut on the wrong axis it comes out grey.
Gemini
A different colour down each of three axes.
Turn it and it runs from violet-blue to smoky grey to nearly colourless, because cordierite shows a different colour down each axis. Thin slices work as a polarising filter, which is the basis of a serious argument that Norse navigators found the sun through cloud with it. Cut it wrong and it comes out grey.
Cancer
Finding the sun through overcast, and getting home.
Thin slices of cordierite polarise light, which is the basis of a serious argument that Norse navigators used it to find the sun through overcast and get home. Turn it and the colour runs from violet-blue to grey to almost nothing. The archaeological case is still contested.
Leo
Cut it on the wrong axis and it comes out grey.
Cut it on the wrong axis and it comes out grey. Iolite is so strongly trichroic that turning it swings the colour from violet-blue to smoky yellow to almost nothing, all visible without instruments. There is a serious argument that Norse navigators used thin slices to find the sun through cloud.
Virgo
Cut it off-axis and the finished stone comes out grey.
Rotate it under a single light and it runs violet-blue, then smoky grey-yellow, then close to colourless, across three axes. Nothing else at this price does that. Cutters have to orient the rough precisely or the finished stone comes out grey. Thin slices work as a polarising filter.
Libra
Three faces, and only one of them sells.
Cordierite, and the whole identification is trichroism: turn it and it runs violet-blue, then smoky grey-yellow, then nearly colourless, all visible without instruments. The cutter has to orient it precisely or the finished stone comes out grey. Three faces, and only one of them sells.
Scorpio
Three different answers along three axes.
Turn it and the colour runs violet-blue, then smoky grey-yellow, then nearly colourless, three different answers along three axes. There is a serious argument that Norse sailors used thin slices as a polarising filter to find the sun through overcast. Cutters must orient it precisely or it comes out grey.
Sagittarius
Norse sailors may have used it to locate the sun through overcast.
Thin slices act as a polarising filter, and there is a serious argument that Norse sailors used it to locate the sun through overcast. Rotate one and it goes from violet-blue to smoky grey to nearly colourless across three axes. Cutters have to orient it precisely or it comes out grey.
Capricorn
Cut at the wrong angle, it comes out grey.
Turn it and it runs violet-blue to smoky grey-yellow to nearly colourless, all three visible without instruments. Thin slices act as a polarising filter, and there is a serious if contested argument that Norse sailors used it to find the sun through cloud. Cut it at the wrong angle and it comes out grey.
Aquarius
Thin slices act as a polarising filter.
Turn it and it runs violet-blue, then smoky yellow-grey, then nearly colourless, all in one stone and all visible without instruments. Thin slices act as a polarising filter. That is the basis of a serious and still-argued case that Norse sailors used it to find the sun through cloud.
Pisces
Cutters must orient it precisely or it comes out grey.
Turn it and it goes from violet-blue to smoky yellow to nearly nothing, all in one stone, which is why cutters must orient it precisely or it comes out grey. Thin slices polarise light, and there is a serious argument that Norse sailors used that to find the sun through overcast.
Correspondences
What tradition attaches to this stone. Folklore, not chemistry.
Element
air
Planet
Saturn
Chakra
third-eye, throat
Signs
sagittarius, libra, taurus, virgo
What tradition says
In crystal lore, iolite is associated with finding one's bearings and with seeing clearly through confusion, the Viking sunstone tradition, though the archaeological case is debated.
Care
- Water is fine. Dry it afterwards.
- Hard but with a distinct cleavage direction that makes it prone to splitting on impact. Warm soapy water; avoid ultrasonics and knocks.
Common questions
What does iolite mean?
Iolite is carried for intuition, clarity and communication. Cordierite, transparent and violet-blue, and famous for a story that may well be true: thin slices act as a polarising filter, and there is a serious argument that Norse navigators used it to locate the sun through overcast.. Tradition links it to the third-eye, throat chakra.
Is iolite real or fake?
Iolite is not faked often, but it is still worth checking. Rotate it under a single light. Iolite goes from blue to grey-yellow to almost clear across three axes; tanzanite shifts blue-violet-burgundy but never to colourless-grey, and is softer (6.. Essentially never treated, another gem sold as-found.
Can iolite go in water?
A short rinse is fine for iolite, then dry it.
Uncommon · violet-blue, grey-blue, smoky indigo, near-colourless from one angle
Where this leads
FOR ENTERTAINMENT AND REFLECTION. NOT MEDICAL, PSYCHOLOGICAL, FINANCIAL OR LEGAL ADVICE. How this works