Alexandrite: The Gemstone That Changes Color

Alexandrite is a fascinating gemstone celebrated for its remarkable color-changing ability, a phenomenon known as pleochroism. This unique characteristic makes it one of the most captivating and sought-after gems in fine jewelry. Discovered in the Ural Mountains of Russia, it was named in honor of the then-heir to the Russian throne, Alexander II. Alexandrite is a variety of the mineral chrysoberyl, and its color change is caused by the presence of trace amounts of chromium. In daylight or fluorescent light, it typically appears greenish or bluish-green, while in incandescent light or candlelight, it transforms to a rich reddish-purple or raspberry hue. This dramatic shift is what makes alexandrite so special and valuable.

Key Features

The defining characteristic of alexandrite is its distinct color change. The quality of this change is a primary factor in its value. Key features include:

• Color Change: The most significant feature. The stronger and more distinct the color change, the more valuable the stone. The ideal change is from a vivid green to a vivid red.
• Hardness: Alexandrite ranks 8.5 on the Mohs scale of hardness, making it quite durable and suitable for everyday wear in jewelry. It is harder than sapphire and ruby, but softer than diamond.
• Clarity: Like most colored gemstones, clarity is important. Eye-clean stones are preferred. Minor inclusions are acceptable, especially in larger stones, as long as they do not detract from the stone's beauty or durability.
• Cut: The cut significantly influences how well the alexandrite displays its color change. Well-cut stones maximize brilliance and the saturation of colors in different lighting conditions. Oval, emerald, and cushion cuts are common.
• Carat Weight: Larger alexandrites are rare, and their price increases significantly with size. Most alexandrites found are relatively small.
• Pleochroism: This is the scientific term for the color change. Alexandrite exhibits strong pleochroism, showing different colors when viewed from different angles.

Origin and History

Alexandrite was first discovered in 1830 by Finnish mineralogist Nils Gustaf Nordenski sld in the Ural Mountains of Russia. Legend has it that the gem was found on the day the future Tsar Alexander II celebrated his birthday, leading to its naming in his honor. Initially mistaken for emerald due to its green color in daylight, its true identity was revealed when it showed a striking red color under lamplight that evening. This discovery coincided with a period of intense national pride in Russia, and the gem quickly became a symbol of the Romanov dynasty, often worn by the Imperial family. Its association with the Tsar and its rare, captivating color change cemented its status as a precious gemstone. After the Russian Revolution, major mining in the Urals ceased, and significant new sources were later discovered in Brazil, Sri Lanka, and East Africa.

Types / Variations

While alexandrite is a specific variety of chrysoberyl, the intensity and range of its color change can vary significantly. These variations primarily relate to the quality of the color change and the dominant hues present:

• Fine Alexandrite: Exhibits a dramatic and distinct color change, often from a vibrant green to a vivid red. These are the most sought-after and valuable.
• Matte Alexandrite: Shows a less pronounced color change, or the colors may be less saturated.
• Brownish or Grayish Alexandrite: These stones may have a color change, but the underlying tones are muted, making them less desirable.
• Synthetic Alexandrite: These are lab-created stones that mimic the color-changing properties of natural alexandrite. They are chemically identical but lack the rarity and provenance of natural stones.
• Color-Change Chrysoberyl: Some chrysoberyls exhibit color change but are not colored by chromium and thus do not meet the strict definition of alexandrite. These are often less dramatic in their shift.

How It's Made

Alexandrite is a natural gemstone, a variety of chrysoberyl. Its unique color and color-changing properties are due to its chemical composition and the presence of trace elements. Chrysoberyl has the chemical formula BeAl2O4 (beryllium aluminum oxide). Alexandrite specifically contains small amounts of chromium (Cr3+) ions substituting for aluminum ions in the crystal lattice. These chromium ions are responsible for absorbing certain wavelengths of light and reflecting others. The specific way these ions interact with light, combined with the presence of other elements like iron and titanium, causes the dramatic color shift. The stone forms in igneous rocks, often pegmatites, and in metamorphic rocks like mica schists. Natural alexandrite is formed deep within the Earth over millions of years under specific geological conditions.

Grading & Quality Standards

Like other precious gemstones, alexandrite is graded based on several factors, primarily focusing on its color and color-changing ability. The key grading criteria are:

• Color Change: This is the most important factor. Gemologists assess the quality of the color change based on the vividness and range of colors displayed in different lighting conditions (daylight vs. incandescent). The ideal is a distinct shift from a rich green to a rich red. The stronger the contrast and saturation, the higher the grade.
• Hue: The specific colors observed. Greens and blues in daylight and reds and purples in incandescent light are most desirable.
• Saturation: The intensity of the colors. Vivid colors are more valuable than muted or grayish tones.
• Clarity: Eye-clean is ideal. Inclusions should be minimal and not visible to the naked eye.
• Cut: A well-proportioned cut enhances the stone's brilliance and color play.
• Carat Weight: Larger stones are rarer and thus more valuable, especially if they possess excellent color change.

There isn't a universal grading system like the 4Cs for diamonds. Instead, expert appraisal and comparison to known high-quality examples are used.

Buying Guide

When purchasing alexandrite, keep the following in mind to ensure you acquire a beautiful and valuable stone:

• Color Change: This is paramount. View the stone in both natural daylight and incandescent light (like a warm lamp) to see the full spectrum of its color change. The more dramatic and vivid the change, the better.
• Color Intensity: Look for stones with strong, pure colors. Avoid stones that appear too muddy, grayish, or brownish.
• Clarity: Aim for eye-clean stones. Minor inclusions are acceptable if they don't affect the gem's sparkle or durability.
• Origin: While Russian alexandrite is historically significant and highly prized, stones from other locations like Brazil and Sri Lanka can also be of excellent quality. Be aware that synthetic alexandrite is common, so buy from a reputable dealer who can provide certification.
• Cut: A good cut will maximize the stone's brilliance and its color-changing effect.
• Reputable Dealer: Purchase from a jeweler with a strong reputation. Ask for documentation or a certificate of authenticity, especially for higher-priced stones.
• Price: Alexandrite is a rare and valuable gemstone. Prices vary significantly based on size, quality of color change, and clarity. Be wary of prices that seem too good to be true.

Price Range & Value Factors

Alexandrite is one of the rarer and more expensive colored gemstones. Its value is primarily driven by the quality of its color change, followed by its color saturation, clarity, and carat weight. Key value factors include:

• Quality of Color Change: The dramatic and distinct the shift from green to red, the higher the value. Stones exhibiting a vivid green to vivid red change command the highest prices.
• Color Saturation: Intense, pure colors are more valuable than muted or grayish tones.
• Clarity: Eye-clean stones are significantly more valuable.
• Carat Weight: Alexandrite is rare in larger sizes. Prices increase exponentially with carat weight for stones with good color change. A 1-carat fine alexandrite can be worth many times more than a 0.5-carat stone of similar quality.
• Origin: Historically, Russian alexandrite was the most prized, but high-quality stones from Brazil and other sources are also valuable.
• Treatments: Alexandrite is rarely treated, which contributes to its value. If any treatments have been applied (which is uncommon), it should be disclosed and will affect the price.

Prices can range from a few hundred dollars per carat for smaller stones with less dramatic color changes to many thousands of dollars per carat for exceptional, large stones with vivid color shifts.

Care and Maintenance

Alexandrite is a durable gemstone (8.5 on the Mohs scale), making it suitable for most types of jewelry. However, proper care will ensure its longevity and beauty:

• Cleaning: Use a soft brush, warm water, and mild dish soap to clean your alexandrite jewelry. Rinse thoroughly and dry with a lint-free cloth. Avoid ultrasonic cleaners and steam cleaners, as these can potentially damage the stone or its setting.
• Avoid Harsh Chemicals: Remove jewelry before engaging in activities that involve harsh chemicals, such as cleaning with bleach or ammonia, or swimming in chlorinated pools.
• Protect from Impact: While durable, alexandrite can still chip or crack if subjected to hard impacts. Store your jewelry in a soft pouch or a separate compartment in a jewelry box to prevent scratches and damage.
• Regular Inspection: Periodically check the setting to ensure the gemstone is secure. If you notice any looseness, have it professionally inspected and tightened.

Pros and Cons

Alexandrite offers unique advantages and some potential drawbacks for jewelry buyers:

Pros:

• Unique Color Change: Its most significant appeal, offering two distinct colors in one gem.
• Durability: With a Mohs hardness of 8.5, it is suitable for everyday wear.
• Rarity: Fine quality alexandrite is rare, making it a valuable investment and a unique choice.
• Symbolism: Historically associated with royalty and good fortune.
• Investment Potential: High-quality stones can hold or increase in value over time.

Cons:

• Price: High-quality alexandrite is expensive due to its rarity and unique properties.
• Availability: Finding large, fine-quality stones can be challenging.
• Synthetic Imitations: Lab-created versions are common and can be difficult to distinguish from natural stones without expertise.
• Color Change Variability: Not all stones have a dramatic color change; some are quite subtle, affecting their value.

Famous Examples

While specific famous individual alexandrites are not as widely known as famous diamonds or rubies, the historical significance of Russian alexandrite is profound. The Imperial family of Russia, including Tsar Alexander II himself, possessed significant alexandrite pieces. These stones were often set in brooches, pendants, and rings, highlighting their regal status. The rarity of large, fine alexandrites means that many of the most exceptional examples are held in private collections or museums, rarely appearing at public auction. The allure of these stones often lies in their historical provenance and their exceptional color-changing abilities, rather than being tied to a single famous gem.

Common Misconceptions

Several misconceptions surround alexandrite:

• All Alexandrite Changes Color Dramatically: Many stones have a subtle color shift, and not all exhibit the vibrant green-to-red transformation. The intensity and range of the color change vary greatly.
• Alexandrite is Always Expensive: While fine alexandrite is costly, stones with less dramatic color changes, lower clarity, or smaller sizes can be more affordable.
• Synthetic Alexandrite is Fake: While not natural, synthetic alexandrite is chemically and physically identical to its natural counterpart and exhibits the same color-changing properties. It's often used as a more accessible alternative. The key is accurate identification and disclosure.
• Alexandrite is a Diamond Imitation: Alexandrite is a distinct gemstone with its own unique properties and beauty, not an imitation of diamond.

Related Terms

• Chrysoberyl
• Pleochroism
• Color Change Gemstone
• Beryllium Aluminum Oxide
• Synthetic Gemstone
• Color Saturation
• Mohs Hardness Scale

FAQs

What is Alexandrite?

Alexandrite is a rare variety of the mineral chrysoberyl, famous for its dramatic color-changing property, known as the alexandrite effect. It appears greenish in daylight and reddish under incandescent light.

Why does Alexandrite change color?

The color change is due to the presence of trace amounts of chromium ions in the crystal structure of chrysoberyl. These ions absorb certain wavelengths of light and reflect others, and the effect is amplified by the way the gem interacts with different light sources (daylight vs. incandescent).

Is Alexandrite a valuable gemstone?

Yes, fine quality alexandrite is very valuable, especially stones with a strong color change, vibrant colors, good clarity, and larger carat weights. Its rarity contributes significantly to its high price.

How can I tell if Alexandrite is real?

Distinguishing natural alexandrite from synthetic or imitation stones often requires expert knowledge and specialized equipment. Key indicators include observing the quality of the color change, checking for natural inclusions (synthetics often lack them or have gas bubbles), and looking for specific refractive indices. Purchasing from a reputable jeweler with a gemological certificate is the safest approach.

What is the difference between Alexandrite and other color-changing gems?

While other gems like sapphire and garnet can exhibit color change, alexandrite's change is typically more pronounced and distinct, often shifting between green and red hues. The mineral composition of alexandrite (chrysoberyl) is also different from sapphire (corundum) or garnet.