Alexandrite Buying Guide
Phenomenal color change and extreme rarity make alexandrite one of the world’s most coveted stones. Appearing green in sunlight and red in artificial light, this gem was first mined in the 1830s and named after Czar Alexander II. Since the stone resembled Imperial Russia’s military colors, it soon became popular. Better yet, this June birthstone has great durability, making it an excellent choice for jewelry.
However, alexandrite’s extreme rarity drives prices very high. Even synthetic alexandrite doesn’t come cheap. Still, this gem’s dramatic color change makes it an exciting addition to any collection.
Alexandrite Buying and the Four Cs
The IGS alexandrite value listing has price guidelines for faceted alexandrite at top, medium, and slight color changes, as well as for cabbed plain and cat’s eye alexandrite with strong color change.
Color Change in Alexandrite
By day, alexandrite should be emerald green to peacock blue. By night, a ruby red or amethyst hue. The intensity of this color change is the most important factor in alexandrite price. Still, intense and complete color changes occur rarely in this stone. Most alexandrites appear muddied in one type of lighting. Thus, the most prized stones undergo a complete shift from lovely green to luscious red. For example, watch the transition of this platinum ring with alexandrite, green sapphires, and diamond accents.
This alexandrite starts green in daylight, then shifts to a deep red in incandescent light. Video © J. Grahl Design. Used with permission.
Some gemological laboratories quantify this shift by a percentage. A 100% change means that the entire stone undergoes color shift. Most high-quality alexandrites exhibit 85-95% change, meaning that some facets don’t change color. However, these results are difficult to reproduce because of the lack of standards in lighting and color.
Lighting Conditions and Alexandrite Buying
When purchasing an alexandrite, pay attention to the lighting. Above all, ask about the color temperature of the light bulbs used. Bulbs with 3000-3300K are incandescent light, and 5000-6500K can simulate daylight. Be aware that simulated daylight can be more flattering than natural sunlight. Thus, if possible, view the alexandrite outdoors.
Tones and Color Change
For this gem, darker tones tend to correspond to a more intense color change. Tones of 75-85% are ideal. Most gems exhibit tones of 40-60%, with color changes from a light green to pinkish hues.
Grey or brown often tempers the stone’s hues. This occurs more often in larger stones.
Alexandrite or Color-Change Chrysoberyl?
No strict standard exists for distinguishing between alexandrite and color-change chrysoberyl. However, the presence of chromium is essential. If the stone doesn’t change from bluish green to red or reddish purple, it may be a color-change chrysoberyl. These gems, though exciting and beautiful, are less rare than alexandrite and much less expensive. Always request a certificate from a gemological laboratory to ensure that the gem is an alexandrite.
Sources and Color Change
Different sources of alexandrite produce gems with different hues of color change. Material from the original deposit in Russia is scattered, and few gems are available to determine the color change quality. Still, the color change must be strong enough to resemble the Czarist colors of red and green.
Nowadays, most alexandrite originates in India. Indian material tends to exhibit excellent green-blue daylight hues with weak color change. However, strong color changing specimens do occur.
Brazilian stones set the standard in the current market, with blue-green hues transitioning to raspberry red. Pinkish tones are less desirable than the purplish secondary hues. Material from Hematita sometimes displays a peacock blue hue in daylight, with only secondary green hues.
Tanzanian gems, though small, often exhibit excellent color change. These transition from green to reddish purple, showing both colors in mixed light. Furthermore, you can generally find these at bargain prices compared to Brazilian material of similar quality.
Sri Lanka, Madagascar, Zimbabwe, and Australia also produce alexandrite, but in small, sporadic quantities.
Alexandrite is a Type II gemstone. Accordingly, gems are generally not eye-clean, and stones with small flaws are often set in jewelry. In fact, rutile inclusions may enhance the color change in alexandrite, resulting in a higher overall price. When choosing a stone, some may prefer a clearer specimen with lesser color change to a heavily included gem.
Due to the rarity of the gem and its tendency to have inclusions, most alexandrite isn’t very well cut. Stones cut for weight retention are often asymmetrical, and even these hold value if the gem is high quality. Oval and cushion cuts are the most common cuts for alexandrite.
Alexandrites above 0.25 carats are rare, but specimens of 10 carats and larger are available. Generally, larger stones exhibit weaker color changes and lesser clarity. Consequently, prices increase rapidly for larger stones of good quality.
Cat’s Eye Alexandrite
Like other chrysoberyl, alexandrite can exhibit a rare cat’s eye effect. Here, darker tones are generally preferred to enhance the bright cat’s eye. A cat’s eye with strong color change is similar in price per carat to a small, faceted stone with medium color changes.
Czochralski´s Pulling Method
This method for synthesizing gem material involves slowly pulling a seed crystal out of melt. It can produce very large, eye-clean crystals. Once magnified, bubble inclusions and curved striations become visible. While an alexandrite produced by Czochralski method is cheaper than a natural stone, this is still an expensive method of gemstone creation.
Flux Grown Crystals
Alexandrites grown using flux methods have inclusions difficult to distinguish from natural inclusions. Still, you may find some flux seed material and see banding or growth lines. An experienced gemologist can identify flux-grown specimens.
Some unscrupulous vendors will sell any stone that changes color as an alexandrite. Be wary of bargains. Also, always obtain a report from a gemological laboratory for a major purchase.
Most commonly, synthetic color-change sapphire gems are passed off as alexandrites. These specimens contain vanadium to induce a blue to purple color change and were widely sold in the early 1900s. Even today, much of the material advertised online as “synthetic alexandrite” is this material.
Color-change garnets are spectacular in their own right. Garnet gems that change color generally change between colors adjacent on the color wheel, with a wide variety in colors available. Although also rare, the cost of these gems doesn’t come close to that of alexandrites.