One of the most extraordinary and rare gemstones we are able to bring you at Gemporia, Cats Eye Alexandrite is every gem collector’s dream. With striking chatoyancy and colour change, this doubly-phenomenal gem is an extraordinary treasure.
What is Alexandrite?
If you’re not already familiar with Alexandrite, it is a highly sought-after gemstone from the Chrysoberyl family. Known as the ‘Emerald by day, Ruby by night’ gem, Alexandrite was first discovered near the Tokovaya River in the Ural Mountains of Russia on the day Alexander II (1818-1881) came of age. Named after the 16 year old future Tsar, the gemstone’s fascinating red to green colour change echoed the colours of the Russian flag at the time.
At first, it was thought that the discovery was a new variety of Emerald, but when it was taken Finnish mineralogist Nils Gustaf Nordenskiold for analysis, he noticed its colour change under candle light as he was working late one night. He correctly realised that it was in fact a new form of Chrysoberyl.
These days, although there are a few more locations where this gem is found, it is still so rare that many jewellers won’t ever have seen one. The addition of the Cats Eye effect makes Cats Eye Alexandrite doubly rare.
What is the Cats Eye Effect?
Some Alexandrite will display ‘chatoyancy’. This phenomenon, named after the French ‘oeil de chat’, meaning ’cat’s eye’, is a stunning, mysterious looking effect, prized by many collectors. A single band of light crosses the top of the gem, appearing to magically open and close as the gem is turned in the light.
Chatoyancy is caused by light reflecting off the thin parallel inclusions within a gem, known as ‘silk’. These inclusions can be hollow tubes, or other structures aligned in one direction. The effect is created at 90° to these. The best analogy is picturing a spool of silk thread and the light reflecting in a band from the surface.
Only a small proportion of gemstones can display a strong chatoyancy and they must be carefully cut en cabochon in the right orientation to show off the effect.
Cats Eye Alexandrite can sometimes show a further phenomenon – the ‘Milk and Honey’ effect is when there is a slightly different colour or opacity shown on either side of the central line of chatoyancy.
What are Cats Eye Alexandrite’s Value Factors?
The very best examples of Cats Eye Alexandrite show a clear, distinct, straight line of chatoyancy running centrally across the gem’s surface. Samples will also have the desired green or blueish-green colour by day and a red or purpleish-red colour under candlelight.
You may also see examples of Cats Eye Chrysoberyl on the market. Although this is a very similar, closely related gemstone, Cats Eye Chrysoberyl (sometimes called Cymophane) will be yellow to yellowish-green in colour and will usually have a wavy or hazy line of chatoyancy. Although this is a beautiful gem in its own right, it is not as treasured among collectors as it doesn’t possess the sought after colours of Alexandrite.
How does Alexandrite’s Colour Change Work?
Alexandrite’s colour change isn’t unique in the gem world, however it was the first discovered and remains the most famous example. Other gemstones displaying the effect are sometimes said to have the ‘Alexandrite effect’. It is, however, one of the most striking colour changes of all. So how does it work?
‘Colour change’ is a bit of a misnomer in the gemstone industry. Gemstones do not actually change colour as such, rather the eye’s perception of their colour changes in different lighting conditions.
In the case of Alexandrite, this effect is caused by chromium impurities within the gem. This causes two different bandwidths of light through the gem in an equal balance – green and red. Daylight contains more green light, so more green light is returned to the eye. Incandescent light contains more red light, so more red light is returned to the eye.
Why is Alexandrite so Treasured?
One of the most collected gemstones of all time, Alexandrite is beloved across the world. If you hold one in your hand, it feels special, its preciousness is almost visceral. It is a firm favourite across the gem industry too:
“This is the very first gemstone I invested in. You have collected something many a gemmologist will have never seen.”
Steve Bennett, Gemporia CEO.
“Things change as the years go by, but one thing that remains the same is the choice gem for eclectic gem aficionados and gem dealers. This gem in simply perfect. I do not think there is a gem in existence that expresses both rarity and understated beauty than this gem.”
Yianni Melas, veteran Gem Explorer.
“Ask the mirror on the wall which is the rarest gemstone of them all? If the answer is not Alexandrite, trade in the mirror.”
Richard Wise, world renowned Gemmologist.
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