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Learning Library

Alexandrite Gemstone

What is Alexandrite?

A very valuable and rare Colour Change Chrysoberyl. It is highly regarded by gem experts, enthusiasts and connoisseurs alike.


The gem’s uniqueness and value is not often apparent at first sight, but finely faceted, one carat pieces or more rank amongst the most expensive gems in the world – far rarer than even fine Diamonds, Rubies, Emeralds and Sapphires.

It is said that Alexandrite was discovered near the Tokovaya River in the Ural Mountains of Russia, on the same day that Alexander II (1818-1881) came of age. Hence the gemstone was named after the 16 year old future Tsar. This was deemed appropriate not just because it was discovered on Russian soil, but also because its extraordinary ability to change colour from red to green echoed the colours of the Russian flag at that time.

The first person to raise its awareness in public, Count Lev Alekseevich Perovskii (1792-1856), believed the stone to be a variety of Emerald, but noting it had a strange mineral content, passed it for a second opinion to the Finnish mineralogist, Nils Gustaf Nordenskiold.

When initially studying the gem, Nordenskiold was also of the opinion that it was a type of Emerald, but as he was confused by its greater hardness he continued to review it. One evening when working by candle light, he was surprised to see the gem was no longer green but had turned a raspberry red. He then declared the gemstone a new form of Chrysoberyl, which would later be given its own distinct name. Today we know that Alexandrite is in fact a colour change variety of Chrysoberyl.

But now for some bad news! It is a misconception that gemstones that are named “colour change” gemstones physically change colour. The reality is that when viewed under different lighting conditions, the gem only appears to change colour. When you buy a “colour change” gemstone, to view the strongest change you need to view the gem under candescent lighting (direct sunlight), which has high proportions of blue and green light, and then immediately view it under incandescent lighting (for example a light bulb), which has a higher balance of red light. Therefore, when you view Alexandrite in daylight the gem appears green, but when the light source is reddish (incandescent), the gem shows hues of purple or red. Effectively you are looking at an optical illusion! Most changes are incredibly subtle, so the saying that Alexandrite looks like Emerald by day and Ruby by night, is a little bit of an exaggeration. That said, Alexandrite is a real treasure: so incredibly rare that few jewellers have ever even held a piece!

Not only does Alexandrite have the ability to change colour, it is also a pleochroic gemstone; this means different colours can be seen when the gem is viewed from different angles. The gem is also very durable, measuring 8.5 on the Mohs scale, making it ideal for setting into all types of precious jewellery.

It is also one of three birthstones for the month of June (Pearl and Moonstone being the other two). In times of upset Alexandrite is believed to strengthen the wearer’s intuition, and thus helps find new ways forward where logic and practical thinking will not provide an answer; it is also known to aid creativity and inspire one’s imagination.

Although Alexandrite was originally discovered in Russia, other mines of this treasured gem have since been discovered in Brazil and Zimbabwe. More importantly, finds in Sri Lanka and India are providing great interest for those in the gem industry, as they are believed to be part of the same vein running down vertically from the original source in the Ural Mountains. However, many gemmologists still believe a fine example known undisputedly to have come from Russia is a real rarity with enormous value.

The number one criterion in valuing Alexandrite for me is the amount of colour change, combined with its clarity and then its size. I would happily pay more for a half carat piece which demonstrated an obvious colour shift, than a one carat piece where you had to use your vivid imagination to see any difference. Generally speaking cloudy Alexandrites have more chance of a stronger colour change than clear ones, but if you can find one that has a clean crystal structure and a vivid colour change then you are indeed looking at a very rare gem.

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Alexandrite viewed in daylight.

Alexandrite viewed in artificial light.

 

 

Russian Alexandrite.

 

 

Alexandrite mine in Tanzania.