Alexandrite is a rare and captivating variety of chrysoberyl, celebrated for its remarkable ability to change color depending on the light source. Appearing green in daylight and shifting to red under incandescent light, this gemstone has fascinated collectors and jewelry enthusiasts for nearly two centuries. Its unique optical properties, combined with its relative scarcity, position it as a highly prized gemstone, comparable in desirability and value to diamonds and rubies. As a June birthstone and the recognized stone for a 55th wedding anniversary, alexandrite holds both personal and historical significance.
History and Lore
The story of alexandrite begins in the Ural Mountains of Russia in the 1830s. Its discovery coincided with the reign of Tsar Alexander II, and the gemstone was quickly named in his honor. The stone’s striking color change – displaying the red and green of the Russian imperial flag – cemented its status as a symbol of Russian royalty and national pride. The initial find occurred in the emerald mines near the Tokovaya River, where miners initially mistook the stones for emeralds due to their intense green hue. It was the Finnish mineralogist Nils Nordenskiöld who recognized the gem’s unique property: a dramatic shift to red when exposed to the light of a campfire.
The demand for alexandrite surged following its discovery, leading to extensive mining operations in the Ural Mountains. However, these deposits were eventually depleted, making alexandrite from this region exceptionally rare and valuable today. While the original Russian alexandrite remains the most sought after, deposits have since been found in Sri Lanka, Brazil, East Africa, India, Burma, Rhodesia, Zambia, and Zimbabwe. Alexandrite sourced from Brazil is considered the closest match in quality to the original Ural Mountain stones. Pieces featuring Ural Mountain alexandrite are now rarely seen, appearing primarily at auction houses.
Geological Formation and Sources
Alexandrite is a form of chrysoberyl, a beryllium aluminum oxide (Be₃Al₂(SiO₃)₆). The color change in alexandrite is attributed to the presence of chromium within its crystal structure. While chrysoberyl itself is relatively common, the presence of chromium is what creates this unique optical phenomenon.
Initially discovered in the Ural Mountains of Russia, alexandrite has since been sourced from several other locations worldwide. These include Sri Lanka, Brazil, East Africa, and India. The Ural Mountain alexandrites are particularly esteemed due to their superior gem quality and intense color shift. More recently, a single mine in Brazil has yielded stones that closely resemble those from the original Russian deposits.
Gemological Properties
Alexandrite possesses a number of distinct gemological properties that contribute to its value and desirability. It registers 8.5 on the Mohs hardness scale, making it a durable gemstone suitable for everyday wear. Its crystal system is orthorhombic, and it exhibits a refractive index ranging from 1.744 to 1.755. The specific gravity of alexandrite falls between 3.68 and 3.73.
The gemstone displays strong pleochroism, meaning it exhibits different colors when viewed from different angles – specifically green, yellow, and red hues. It also exhibits weak fluorescence, typically glowing green under ultraviolet (UV) light. Alexandrite has imperfect cleavage and a conchoidal fracture pattern.
The quality of alexandrite is largely determined by the strength of its color change. A high-quality stone will exhibit a near 100% color change, shifting dramatically between green and red. Anything above a 30% color change is considered acceptable, while stones with less than 30% color change are generally not considered true alexandrite. Available color ranges include primary hues of green and red, with secondary modifications of yellow and blue. Premium colors feature strong green and red transitions.
A table summarizing key gemological properties is provided below:
| Property | Value |
|---|---|
| Chemical Formula | Be₃Al₂(SiO₃)₆ |
| Hardness (Mohs) | 8.5 |
| Crystal System | Orthorhombic |
| Refractive Index | 1.744 - 1.755 |
| Specific Gravity | 3.68 - 3.73 |
| Pleochroism | Green, Yellow, Red |
Symbolism and Metaphysical Beliefs
Beyond its aesthetic appeal, alexandrite is believed to possess various symbolic and metaphysical properties. It is associated with love, luck, and good fortune, and is often given as a gift to celebrate a 55th wedding anniversary, symbolizing enduring affection.
Alexandrite is also closely linked to the crown chakra, believed to promote intuition, creativity, imagination, and a deep connection to the universe. The gemstone is thought to bring joy, hope, and a sense of purpose to those who wear it. Furthermore, alexandrite is believed to harmonize opposing forces, bridging the gap between the physical and spiritual realms.
Care and Cleaning
Due to its hardness of 8.5 on the Mohs scale, alexandrite is a relatively durable gemstone. However, it is still susceptible to scratches and damage from harsh impacts. To maintain its brilliance, alexandrite jewelry should be cleaned regularly with warm, soapy water and a soft brush. Avoid ultrasonic cleaners and harsh chemicals, as these can damage the stone. It is also advisable to store alexandrite jewelry separately from other gemstones to prevent scratching.
Conclusion
Alexandrite stands as a testament to the beauty and rarity found within the natural world. From its serendipitous discovery in the Ural Mountains of Russia to its enduring status as a June birthstone and symbol of lasting love, this color-changing gemstone continues to captivate and inspire. Its unique optical properties, combined with its historical significance and metaphysical associations, make alexandrite a truly exceptional and highly valued gem.