Alexandrite is one of the most unusual gems in the world. You may have heard it being referred to as an ’emerald by day’ and a ‘ruby by night’. This is due to its remarkable color-change ability, which allows it to transform from green in daylight to red in incandescent light.
However, June’s modern birthstone is so rare and expensive that few have ever seen or even heard of alexandrite.
Below, you can find a comprehensive overview of this fascinating variety of chrysoberyl, which makes an excellent stone for jewelry (if you are lucky enough to get your hands on one).
Alexandrite was discovered in Russia’s Ural Mountains in 1833. It was then that this unusual green, color-changing gemstone drew the attention of renowned mineralogist Nils Gustaf Nordenskiöld, who was the first to conclude that a new discovery had been made. The stone was named after the young Alexander II, who was next in line to inherit the Russian throne.
This early association with the Csars is likely what caused the gem to gain prestige in the public eye. It also caught the country’s attention because its green and red hues reflected Russia’s military colors. As a result, alexandrite became the official gemstone of Imperial Russia’s Tsardom.
By the 1950s, alexandrite had become the modern alternative to June’s traditional birthstone, which is the pearl.
The most obvious identifying characteristic of alexandrite is the color change phenomenon that occurs when it is exposed to different kinds of light. Typically, gemologists use an alexandrite’s color in natural sunlight as the reference point for grading its color change. This means that the standard alexandrite color change is green in sunlight and red in incandescent light. However, other types of lights can produce other colors.
Alexandrite is an extremely rare gem primarily due to the circumstances necessary for its formation. Alexandrite requires beryllium (Be), one of the rarest elements on the planet, and chromium (Cr) to form. However, beryllium and chromium rarely occur in geological conditions where they can interact, hence the rarity of these gems.
Besides the extraordinary circumstances necessary for its formation, the other main reason why alexandrite is extremely rare is that only a few sources of this gem remain, and even these only yield a handful of gem-quality specimens per year. As a result, the primary source of natural alexandrite gems today is antique jewelry.
Alexandrite is rated an 8.5 on the Moh’s hardness scale, making it quite a durable stone that is suitable for a wide range of jewelry settings. However, alexandrite is still prone to scratches and dents from other, harder gemstones and is sensitive to extreme heat, so some care is required to ensure the longevity of the stones in alexandrite jewelry.
There are no known treatments for enhancing the beauty of natural alexandrites.
Alexandrite is a member of the chrysoberyl species, which is capable of displaying a ‘cat’s eye’ effect when cut as a cabochon. As a member of this species, alexandrite can also display a cat’s eye effect. Though not limited to a particular region, these types of gems are extremely rare.
The physical and optical properties of alexandrite can vary according to its source. For this reason, we have included the following section to discuss some of the most common regional varieties of alexandrite.
As the original source of this unusual gem, Russia is the most coveted origin for alexandrite.
In fact, the adage, ’emerald by day, ruby by night’, is likely to have been coined in the presence of Russian alexandrite, which is famous for its dramatic color change from green in daylight to red in incandescent light.
Nowadays, finding gem-quality Russian material over one carat is nearly impossible. This is because the majority of rough that is produced is usually emerald, and any presence of alexandrite is typically of low quality.
Additionally, the blue-green hue of Russian stones can be easily confused with other regional varieties.
Around 150 years after the first alexandrite was unearthed in Russia, a significant deposit was found in Brazil. The discovery quickly drew a large number of independent miners to the area and, after a mere 12 weeks of excavating, the supply of alexandrites had already dwindled. Since then, the production of alexandrite stones over one carat is virtually unheard of.
Brazilian alexandrites generally appear pale in color, ranging from blue-green to mauve. However, some fine-quality gems exhibit a rich bluish-green in daylight and transform into an intense purple under incandescent light.
Alexandrites from India are well-known for their distinctive grass-green color in the daylight. Their incandescent color is typically less intense and can be described as medium to light in saturation.
Today, most Indian alexandrite originates from the state of Odisha and comes in small sizes (less than half a carat).
Despite the limited production, the occasional blue-green to rich purple alexandrite from India is unearthed.
Some of the finest alexandrite on the market today comes from Madagascar, the island country off the east coast of Africa. These stones typically appear blue-green under daylight and purplish-red under incandescent light.
Lower-grade alexandrite from Madagascar is usually muddy-green and almost always has a brown modifier under incandescent light.
Sometimes referred to as the ‘Island of Gems’, Sri Lanka has the highest density of gemstone deposits of any other country in the world. It is, therefore, unsurprising that the country also produces alexandrite.
Sri Lankan alexandrite tends to have a yellowish-green appearance in the daylight and comes in larger sizes than other regional varieties. However, they typically don’t exhibit a strong color change and often display the same yellowish-green color under incandescent light, just in a lighter hue. So far, large alexandrites with a strong color change from Sri Lanka remain few and far between.
Sri Lankan alexandrite also bears a remarkable semblance to the gems from Madagascar, making it almost impossible to distinguish between the two. To complicate matters, there is a chance that some gems from Sri Lanka are, in fact, from Madagascar.
Local suppliers will occasionally source rough alexandrite from Madagascar and then facet the material in Sri Lanka. Once the stone has been cut and polished, suppliers may lose track of its origins, hence why it is easy to mistake one variety for the other.
Though alexandrite from Tanzania is extremely rare, the specimens that have been found there almost always display a dramatic color change. The colors of the stones range from bluish-green in the daylight to mauve or purplish red under incandescent light.
This variety also shares similarities with top-quality gemstones from both Madagascar and Brazil, making identification difficult.
Like all other gemstones, the price of alexandrite is influenced by several factors. We provide an overview of the main ones below: namely, color, clarity, and carat weight.
Color has a significant impact on the value of an alexandrite gem. When it comes to grading color, gemologists take two factors into account.
The first is the color intensity of the gem. This means that the nearer the color is to pure green and red, the higher the price of the stone. Conversely, blue-green and brownish or purplish-red gems hold less value.
The second factor is how discernible the color change is to the naked eye. Alexandrite can exhibit anything from just a 5% to a 100% color change. Gems that display a 100% color shift from pure green to pure red are inherently more valuable.
Like most other gemstones, the majority of natural alexandrite isn’t suitable for faceting. That being said, the clarity of alexandrite is often overlooked in favor of its color change. This means that clarity has less of an impact on the value of a particular stone.
Let’s compare two alexandrites of equal size as an example. One specimen is an opaque cabochon with a 100% green to red color change, while the other is an eye-clean gem with a 50% blue-green to brownish-red color change. In this instance, the opaque cab will be regarded as the more valuable of the two purely because of its 100% color change.
Unlike clarity, carat weight plays a significant role in evaluating alexandrite. For example, high-quality, natural stones measuring up to one carat can sell for around $15,000 per carat. For stones over one carat, the prices can more than double, ranging from $50,000 to $70,000 per carat. However, the vast majority of alexandrites weigh under one carat.
Fun fact: the largest faceted alexandrite in existence is a 65.7-carat green/red color change stone from Sri Lanka, which is housed at the Smithsonian Institution. The largest alexandrite from Russia’s Ural Mountains tips the scale at around 30 carats.
Other alexandrites of notable size include another two Sri Lankan specimens that reside at the British Museum of Natural History in London. One weighs 43 carats, while the other weighs 27.5 carats. Additionally, some private collectors have reported stones of up to 50 carats, although these accounts are not verified.
Given the rarity of the gem, there exists quite a large market for lab-created alexandrite. These synthetic stones possess the same chemical and physical properties as natural alexandrites and they also cost less to make. In other words, they are cheaper to acquire than their natural counterparts. That being said, they are still among the most expensive synthetic gemstones on the market.
Manufacturers use several different procedures for growing synthetic alexandrites. These include hydrothermal, melt, and flux methods. In some cases, gemologists can identify the type of growth method that was used by examining the inclusions that are present in a particular gem. For example, hydrothermal techniques cause bubbles and liquid inclusions, while melt processes can give rise to curved striae. Lastly, flux growth can result in inclusions of platinum or other seed materials.
Besides synthetic gemstones, there is also quite a significant demand for look-a-likes or simulants. These range from fairly inexpensive synthetic corundum that exhibits an alexandrite-like color change to natural color-change chrysoberyl that can fetch quite a high price (though not as high as alexandrite). Also, note that while alexandrite is a member of the chrysoberyl family, not all color-change chrysoberyls are alexandrites.
Be forewarned: if you come across an alexandrite at a bargain price, there is a good chance that it is either synthetic or a simulant.
Given that alexandrite is a relatively hard stone with a score of 8.5 on the Moh’s scale, it does not require any special care requirements other than keeping it out of direct sunlight and storing it separately from harder gemstones like diamonds.
Alexandrite stones can also be cleaned mechanically or by hand using lukewarm (not boiling!) water with a mild detergent and a soft brush.
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