Are Alexandrites Expensive?

If you say the phrase "emerald by day, ruby by night" to any gemstone professional or collector, they will immediately understand that you are talking about alexandrite. Alexandrite is a gemstone that is part of the gem species chrysoberyl, and it is recognized as one of the most valuable of all phenomenal gems. Their beautiful, color-changing appearance has won them an avid group of fans. This is in spite of the fact that they were discovered only recently and remain one of the rarest gemstones on the market. 

The IGS Gem Price Guide estimates that the average retail price for a alexandrite ranges from about $2,000 per carat for smaller stones to almost $16,000 per carat for larger specimens. The best gems sell at auction for even more than that. When valuing alexandrite, the quality of the color change is the most important factor to consider. The size of the gem and its clarity are other characteristics that influence value.

The Most Important Value Factor for Alexandrite is The Quality of Its Color Change Phenomenon

In the year 1830, Russian miners working in the Ural Mountains stumbled upon a deposit of a previously unknown gemstone that shone a bright green color in daylight but glowed red when illuminated by incandescent light in the evening hours. This new gem was an immediate sensation and was named for Czar Alexander II who ruled at that time. To this day, the most important value characteristic of alexandrite remains the quality of its color-changing property. 

While there are other natural color-change gems like corundum, garnet, and spinel, the best alexandrites have the most pronounced and dramatic color change. This led some in the industry to refer to color change broadly as "the alexandrite effect".

It is important here to differentiate the color change effect from the concept of pleochroism. Alexandrites are pleochroic and show three different colors depending on which angle you look at the crystal. Those colors are most often green, purple-red, and orange. However, the notable color change from green to red that the gem is famous for isn't the result of pleochroism. Rather, it is due to the particular way that alexandrite interacts with, and absorbs, light. The crystal strongly absorbs the middle of the color spectrum, allowing only red and green to reflect out. When lit by a light source with lots of green and blue, like daylight and fluorescent bulbs, that green or bluish green color dominates the appearance of gemstone. Similarly, when the stone is lit by sources with lots of red like incandescent bulbs, all that red is reflected back out.

When considering color in general, gemologists look at three factors: hue, tone, and saturation. The color change of alexandrite only affects its' hue. The green color may be bluish, yellowish, grayish, or brownish while the red may have some purple, orange, or brown. While the red and green hues are strongly expressed in good alexandrite, the hues are not quite as bold as the color of fine green emeralds and red rubies. Whatever tone and saturation are present appear the same regardless of the lighting conditions. 

The most valuable alexandrite gems clearly alternate between a green or bluish-green color in daylight and red to purplish red in incandescent light paired with a medium to medium-dark tone and moderate saturation. That being said, not all alexandrite gems show perfectly distinct colors. As the quality decreases, the color expression becomes less distinct as more gray and brown can be seen. The lowest quality alexandrite gems have a muddy appearance and the color change is minimal.

How Size Affects Alexandrite Value

Already a rare gemstone, large alexandrite crystals are especially scarce with most faceted gems weighing under a carat. As carat weight climbs, so does value. And it rises quickly. In 2011, a massive 11.66 ct. alexandrite sold at auction for $421,501. That is a per-carat value of over $36,000.

Due to the fact that alexandrite is pleochroic, cutters must be careful to orient the gem so that the face-up direction best highlights the green and red hues. If they get this wrong, the gem will have a markedly lower per-carat value than it could. Unfortunately, this means that carat weight must sometimes be sacrificed to achieve maximized color expression, however cutters work very hard to keep as much weight on the gem as possible. As a result, most gems are faceted into some variety of mixed cut utilizing both the kite and triangular facets of brilliant cuts alongside parallel facets that characterize step cuts. 

How Clarity Affects Alexandrite Value

Most alexandrite gems have good clarity with few eye-visible inclusions. Gems that are eye-clean are certainly more valuable than those that do have noticeable clarity features.

There is an exception to this trend. Alexandrite is special in that it is one of only a few gemstones that can exhibit multiple phenomena at the same time. Not only does it show color change, but some gems have many small inclusions that are aligned parallel to each other which creates a cat's eye effect. The inclusions that create the cat's eye - known formally as "chatoyancy" - may be either hollow tubes or very fine needle inclusions. Research has shown that the needle inclusions may be rutile which is a common gemstone clarity feature, but there are other options as well. Gems that are chatoyant are most often cut as cabochons to highlight that special cat's eye.

Alexandrite that shows both impressive color change and a strong cat's eye are very rare and very valuable. 

The Origin of Alexandrites Is Not a Significant Contributor to Value

As alexandrite is already scarce, buyers clamor to purchase whatever gems they can find, regardless of where they come from. While there is overlap in the appearance of gems, some of the various deposits have gained a reputation for distinctive features. The original Russian mines whose gems are thought to be the most beautiful are mostly mined out. The supply chain now relies heavily on Brazilian, Sri Lankan, and East African deposits. 

Brazil - The best Brazilian alexandrites rival the Russian gems in terms of beauty. However, alexandrite mining in this region is risky. An important source located in Minas Gerais was uncovered in the 1980's, but the potential profits caused chaos amongst miners. Conditions became so dangerous that the government was forced to cover the mine. Hopefully, this is a source that can be responsibly mined in the future.

Sri Lanka - Alexandrites from Sri Lanka have a reputation of being some of the largest in the world. Yet the color of many stones isn't the most desirable combination. The green expression tends to include quite a bit of yellow while the red is often paired with more brown than purple. 

How Treatments Affect the Value of Alexandrite

The majority of alexandrite gems are left untreated, so it is not something that buyers generally worry about. The exception is stones that have sizable fractures. These lower-quality gems may be fracture-filled to improve their apparent clarity and make them more salable at lower a price point. Unfortunately, the various materials that are used to fill the fractures are not everlasting. The biggest issue is that they may discolor and/or melt in response to heat. These gems must be treated with care and never cleaned with steam or in an ultrasonic machine.

Final Note on Alexandrite Value

People have been entranced by alexandrites since they were first discovered almost two hundred years ago. Their magical ability to appear so different depending on ambient lighting has mesmerized royals, gem collectors, and the general public. The fact that so many gems boast eye-clean clarity and some are chatoyant adds to their appeal. Their reputation gained them the distinction of being one of the birthstones for the month of June. However, they remain a rare gem which is why good quality stones are so pricy.