Romance, History, and Legend
In gemology, the term "phenomenon" refers to a gemstone's extraordinary beauty, resulting from the interaction of light with its chemical composition or physical structure. Common examples include the star effect (asterism) in sapphires and rubies, or the cat's-eye effect (chatoyancy) seen in tourmaline and chrysoberyl. Other gemstone phenomena include opals' color play, moonstones' adularescence, and labradorite's iridescence (called labradorescence). Alexandrite, highly prized for its color-change phenomenon, is a remarkable gem. As Edwin Streeter once wrote: "The wonderful alexandrite is an emerald by day and an amethyst by night." His awe stemmed from the gemstone's ability to appear green in daylight and transform into a plum red under the warm tones of candlelight or incandescent light. This rare gemstone, discovered in Russia's Ural Mountains in 1833, has long been associated with the Russian royal family and is named after Tsar Alexander II. Since its discovery two centuries ago, alexandrite has been considered one of the rarest and most valuable gemstones in the world.
Origins
For centuries, Russia was the sole source of alexandrite until deposits were discovered in Sri Lanka. Sri Lankan alexandrite exhibits a green hue in daylight but shifts to a brownish-red under incandescent light, rather than the plum red typical of its Russian counterpart. Brazil has become a significant source of alexandrite since its discovery there in 1997, though its color change is often less dramatic than higher-quality Russian stones. Small quantities of alexandrite are also found in India, and gemologists are hopeful for future discoveries in East Africa, Australia, and Asia. However, experts believe that the unique geographic conditions necessary to produce alexandrite make new discoveries unlikely.
Enhancements
While most gemstones are treated to improve color or clarity, no known treatment methods exist to enhance alexandrite's natural beauty.
Choosing a Gemstone
An authentic alexandrite piece is a treasure in any collection. With a hardness of 8.5, alexandrite is suitable for everyday wear, surpassed only by diamonds, rubies, and sapphires in durability. Its durability and rarity make alexandrite an excellent choice for engagement rings or heirlooms. Traditionally, alexandrite over 5 carats has only been found in Russia's Ural Mountains. Other large specimens have been unearthed in India and Sri Lanka, but any alexandrite over 3 carats is exceedingly rare. Most Brazilian alexandrite tends to be smaller, though 1 to 2-carat stones are available. The defining characteristic of high-quality alexandrite is its distinct color change from green to red. Alexandrite selectively absorbs most colors of light while strongly transmitting green and red wavelengths. It appears green under daylight or fluorescent light (with strong blue and green light) and red under incandescent light (ideally candlelight or firelight). The more pronounced the shift from green to red, the rarer and more valuable the gem.
Because of alexandrite's value and rarity, the term "alexandrite" applies only to the chrysoberyl variety that exhibits a color change. Other gemstones showing similar color changes should be marketed as "alexandrite-like" or "color-change" gems. Since the 1970s, labs have been able to produce synthetic alexandrite, which shares the appearance and properties of natural alexandrite but is far less valuable. Another popular alexandrite imitation is synthetic color-change sapphire, which has been manufactured and sold as alexandrite for over a century. Many synthetic alexandrite-like sapphires were sold to tourists in Mexico or Egypt after World War II and remain in circulation today.
For more information, visit the AIDI International Lab-Grown Diamond Association at www.aidi.org. Should you have any questions, feel free to contact us at info@aidi.org.