Alexandrite is a rare and extraordinary gemstone, celebrated for its most defining characteristic: the dramatic change in color from green in daylight to red under incandescent light. This phenomenon, known as the alexandrite effect, makes it one of the most remarkable and valuable members of the chrysoberyl family. As one of the three official birthstones for June, alongside pearl and moonstone, alexandrite offers a unique and captivating choice for those born in the month. Its story is intertwined with imperial Russian history, and its scarcity has cemented its status as a prized collector's gem. This article explores the history, geological origins, gemological properties, and cultural significance of alexandrite, drawing exclusively from authoritative sources to provide a comprehensive overview for gemstone enthusiasts, students, and buyers.
History and Lore
The discovery of alexandrite is a tale of serendipity and imperial grandeur. The gemstone was first identified in the Ural Mountains of Russia in the year 1830, a date consistently cited across multiple sources. It was found near the Tokovaya River and was subsequently named after the future Tsar Alexander II of Russia, who was the heir apparent at the time. The stone's unique color-changing property was reportedly discovered by a young Finnish mineralogist, Nils Nordenskiöld, who observed the stone's green hue transform to a red color under candlelight. This remarkable discovery occurred on the future tsar's birthday, adding to its significance and leading to its adoption as a symbol of the Russian Empire.
Tsar Alexander II, after whom the gem was named, is noted in the historical record for his role in the emancipation of Russia's serfs, a major social reform enacted in 1861. He was also the target of multiple assassination attempts and was ultimately assassinated in 1881. The gemstone's association with this period of Russian history contributes to its mystique and historical value. For decades, the Ural Mountains remained the primary source of fine alexandrite, and the stones from this region are still considered the benchmark for quality, particularly for their vivid color change.
The journey of alexandrite from a Russian imperial treasure to a global gemstone began as deposits were later discovered in other parts of the world. While the Russian sources are historically the most famous, modern alexandrite is also sourced from Sri Lanka, East Africa, and Brazil. Each of these locations yields stones with distinct characteristics, which are discussed in detail in the section on geological sources. The gemstone's status was further solidified when it was officially designated as a birthstone for the month of June, sharing this honor with pearl and moonstone. This recognition has made alexandrite a popular choice for jewelry, especially for those seeking a unique and meaningful gem for June birthdays. It is also traditionally associated with the 55th wedding anniversary, symbolizing a rare and enduring bond.
Geological Formation and Sources
Alexandrite is a variety of the mineral chrysoberyl, with the chemical formula BeAl₂O₄ (beryllium aluminum oxide). Its formation requires a specific geological environment where beryllium and aluminum are present together, which is a rare combination in nature. The presence of chromium is what gives alexandrite its characteristic color and its ability to change color. In its pure form, chrysoberyl is colorless or yellow, but the substitution of trace amounts of chromium for aluminum in the crystal lattice results in the green and red hues.
The primary and most historically significant source of alexandrite is the Ural Mountains in Russia. Russian alexandrite is renowned for its exceptional color change, typically appearing as a vivid emerald green in daylight and a rich red or purplish-red under incandescent light. According to gemological data, Russian material also tends to have higher birefringence and refractive index compared to alexandrite from other sources.
In the 20th and 21st centuries, new deposits were discovered, making alexandrite more accessible, albeit still rare. Sri Lanka has become a significant source, producing alexandrite with a different character. Stones from Sri Lanka often display an olive-green or yellowish-green color in daylight and shift to brownish-red under incandescent light. The birefringence of Sri Lankan alexandrite is noted to be higher than that of material from Burmese, Brazilian, and Zimbabwean sources, while its refractive index is lower than that of Russian and Zimbabwean stones.
Brazilian alexandrite, particularly from the state of Minas Gerais, is another important source. Brazilian stones frequently show a pale blue-green color in daylight and a pale mauve or lavender shade in incandescent light. Some Brazilian alexandrite may also exhibit a significant internal replacement of aluminum by gallium, a chemical variation that can affect its properties. The birefringence of Brazilian alexandrite is generally lower than that of Russian and Sri Lankan material, but its refractive index is higher than that of Burmese and Sri Lankan stones.
Zimbabwe is also noted as a source for alexandrite, with stones from this region often displaying a rich emerald-green color in daylight. The birefringence of Zimbabwean alexandrite is lower than that of Russian and Sri Lankan material, but its refractive index is higher than that of Sri Lankan, Burmese, and Brazilian stones. These regional variations are crucial for gemologists when identifying the origin of a stone and for collectors who may have a preference for the visual characteristics of alexandrite from a specific location.
Gemological Properties
Alexandrite possesses a unique set of physical and optical properties that define its appearance, durability, and value. The following table summarizes its key gemological characteristics, as derived from the provided sources:
| Property | Details |
|---|---|
| Mineral Family | Chrysoberyl |
| Chemical Formula | BeAl₂O₄ |
| Crystal System | Orthorhombic |
| Mohs Hardness | 8.5 |
| Refractive Index | 1.745 - 1.759 |
| Specific Gravity | 3.68 - 3.80 |
| Birefringence | 0.008 - 0.010 |
| Dispersion | 0.015 |
| Cleavage | Distinct/good to poor on {110} |
| Fracture | Conchoidal or uneven/irregular |
| Luster | Vitreous (glassy) |
| Transparency | Transparent to opaque |
| Pleochroism | Present & strong; colors vary by direction |
| Fluorescence | Weak red in SW-UV & LW-UV |
| Optical Effects | Color-change; very rarely chatoyancy or asterism |
Color and the Alexandrite Effect
The most celebrated property of alexandrite is its color change, often described as "emerald by day, ruby by night." This phenomenon is a result of the stone's unique absorption of light. The chromium ions within the crystal structure cause the stone to absorb specific wavelengths of light. In daylight, which is rich in blue and green wavelengths, the stone appears green. Under incandescent light, which is rich in red and yellow wavelengths, the stone appears red. The specific absorption band at 580nm is what allows this shift from red to green under different light sources.
The quality of the color change is a primary value factor. The degree of color change is often measured on a scale from 5% to 100%, with 100% representing a complete shift from one color to its complementary hue. Fine alexandrite is expected to be green to bluish-green in daylight and red to purplish-red in incandescent light. The presence of gray or brown undertones can lower the stone's value, though vibrant shades of purplish-red or blue-green are still considered valuable, as pure green and red colors are exceptionally rare.
Clarity and Cut
Alexandrite is typically found with inclusions. Clean, eye-visible inclusion-free alexandrite is exceptionally rare and commands a premium price. The clarity grade of alexandrite is assessed similarly to other gemstones, with "eye-clean" stones being highly desirable. The distinct to poor cleavage of alexandrite means that it can be susceptible to damage from blows, making skilled cutting essential to maximize the yield from rough material and to protect the stone. Faceted cuts are the most common, designed to highlight the color change and brilliance of the gem. Cabochon cuts are also used, especially for stones that exhibit chatoyancy (a cat's-eye effect), a rare but beautiful optical phenomenon in alexandrite.
Hardness and Durability
With a Mohs hardness of 8.5, alexandrite is a very durable gemstone, suitable for all types of jewelry, including rings that are subject to daily wear. Its hardness is second only to corundum (sapphire and ruby) and diamond among popular gemstones. This durability, combined with its rarity and beauty, makes it an excellent choice for heirloom-quality jewelry.
Symbolism and Metaphysical Beliefs
Beyond its physical properties, alexandrite is steeped in symbolism and has been attributed with various metaphysical properties throughout history. Its most potent symbol is duality and balance, directly stemming from its color-changing nature. The gem is seen as a stone that embodies the harmony between the physical and spiritual worlds, the conscious and the subconscious, and the sun and the moon. This duality makes it a powerful talisman for those seeking balance in their lives.
In Russian lore, alexandrite was considered a stone of good fortune and omen, believed to bring luck and prosperity to its wearer. Its association with the tsar and the Russian Empire added to its prestige and was thought to imbue it with protective qualities. Some traditions hold that alexandrite can promote creativity and inspire imagination, allowing the wearer to see situations from multiple perspectives, much like the stone itself shows different colors under different lights.
As a June birthstone, alexandrite is said to bestow upon those born in this month a sense of joy, intuition, and good fortune. It is also believed to bring emotional balance and calm, helping to alleviate stress and anxiety. For those celebrating a 55th wedding anniversary, alexandrite symbolizes a rare and precious love that has endured and transformed over time, much like the stone's own transformation under light.
While these metaphysical beliefs are not scientifically proven, they are an integral part of the gemstone's cultural history and add to its allure for many collectors and jewelry enthusiasts.
Care and Cleaning
Given its excellent hardness of 8.5, alexandrite is relatively easy to care for and maintain. It is durable enough to withstand everyday wear, but as with all fine jewelry, certain precautions should be taken to ensure its longevity.
Cleaning Methods
The safest way to clean alexandrite jewelry is with warm water, a mild dish soap, and a soft brush. Gently scrub the stone and its setting to remove any dirt, oil, or residue. Rinse thoroughly with clean water to ensure no soap film remains. It is important to avoid harsh chemicals, such as bleach or chlorine, which can damage the stone or its setting. Ultrasonic cleaners are generally safe for alexandrite, but it is always advisable to consult a professional jeweler before using one, especially if the stone is set in a delicate or antique piece. Steam cleaning is not recommended, as the rapid temperature changes could potentially cause damage, particularly if the stone has any inclusions or fractures.
Storage and Handling
When storing alexandrite jewelry, it should be kept separately from other gemstones and jewelry to prevent scratching. While alexandrite is hard, it can be scratched by harder materials like diamond, sapphire, and ruby. It is best to store it in a soft-lined jewelry box or a fabric pouch. When wearing alexandrite rings or bracelets, it is wise to remove them during activities that could subject the stone to hard blows or exposure to abrasive materials, such as gardening, heavy lifting, or working with tools.
By following these simple care instructions, the beauty and integrity of an alexandrite gemstone can be preserved for generations, allowing it to be enjoyed as both a personal adornment and a treasured family heirloom.
Conclusion
Alexandrite stands as a testament to nature's artistry, a gemstone whose very essence is defined by transformation. From its historic discovery in the Russian Ural Mountains to its modern sourcing in Sri Lanka, Brazil, and Zimbabwe, alexandrite has captivated humanity with its unique color-changing ability. Its remarkable hardness of 8.5 makes it a durable choice for jewelry, while its rarity ensures its place as one of the most valuable gemstones in the world. As a birthstone for June, it offers a deeply personal and symbolic choice, representing balance, joy, and good fortune. Whether appreciated for its scientific wonder, its historical significance, or its metaphysical lore, alexandrite remains a gemstone of unparalleled beauty and intrigue, a true masterpiece of the mineral kingdom.