Gemstone Encyclopedia / Alexandrite
The Complete Alexandrite GuideColor change, rarity, chemistry, and what actually determines value
Alexandrite is one of the rarest and most technically fascinating gemstones in existence.
Alexandrite at a glance
Quick facts- Mineral
- Chrysoberyl
BeAl₂O₄ - Color
- Green in daylight, red to purplish red in incandescent light
- Hardness
- 8.5 Mohs
- Birthstone
- June
- Color caused by
- Chromium replacing aluminum in the crystal structure
- Key origins
- Russia, Brazil, Sri Lanka, East Africa
- Zodiac
- Gemini
- Symbolism
- Luck, transformation
- Popular cuts
- PearOvalCushion
Overview
Not simply a “color-changing stone”
Fine stones show green to bluish-green in daylight and red to purplish-red under incandescent light — and in the best stones, the change is immediate, complete, and unmistakable.
Alexandrite is one of the rarest and most technically fascinating gemstones in existence. It is not simply a "color-changing stone" - it is a gemstone defined by how precisely and dramatically it interacts with light. At its highest level, alexandrite shows a distinct transformation: green to bluish-green in daylight and red to purplish-red under incandescent light. This is not a subtle shift. In fine stones, the change is immediate, complete, and unmistakable.
What makes alexandrite exceptional is that it requires multiple rare conditions to occur at the same time. The chemistry must be correct, the crystal must form cleanly, the color must be strong in both lighting environments, and the cut must preserve that performance. If any one of those factors is off, the stone drops dramatically in quality. This is why fine alexandrite is not just rare - it is structurally difficult to form.
The science behind the color change
The effect comes down to chromium standing in for aluminum within the chrysoberyl crystal. Chromium absorbs light in a narrow band of the spectrum, so the stone's appearance shifts with whatever light source it's under: daylight, rich in blue and green wavelengths, reads as green, while incandescent light, rich in red wavelengths, pulls the same stone toward red. The exact balance of chromium and trace elements in a given crystal determines how strong and how clean that shift turns out to be.
Varieties
Alexandrite, cat's-eye, and lab-created
Beyond the daylight-to-incandescent shift above, a few related varieties and look-alikes are worth knowing before you buy.
Alexandrite
Green to bluish-green in daylight on the left, red to purplish-red under incandescent light on the right - the same stone, two light sources.
- Color cause
- Chromium replacing aluminum in the chrysoberyl crystal structure.
- Treatment
- Essentially always untreated - alexandrite's value comes from being natural.
- Rarity and value
- Stones over one carat with a strong, complete color change are exceptionally rare.
- Good to know
- The strength and completeness of the shift matters as much as either color alone.
Cat's-eye alexandrite
Cut as a cabochon rather than faceted, showing a sharp line of light across the dome (chatoyancy) in addition to the usual color change.
- Color cause
- Same chromium-driven color change as faceted alexandrite.
- Treatment
- Untreated.
- Rarity and value
- Rarer than ordinary color-change material - parallel fibrous inclusions have to align well enough for both effects to show at once.
- Good to know
- Not covered in the article, but a real, well-documented variety - and one Forever Rox itself sells, in cat's-eye alexandrite rings and studs.
Lab-created alexandrite
Often displays strong, even dramatic color change - sometimes more dramatic than natural stones - but reads as unusually clean, without natural material's typical inclusions.
- Color cause
- The same chromium-in-chrysoberyl mechanism, grown in a laboratory rather than the earth.
- Treatment
- Not applicable - it's synthetic rather than treated.
- Rarity and value
- Widely available and inexpensive relative to natural stones; the key difference from natural alexandrite is origin, not chemistry.
- Good to know
- For buyers, understanding this distinction is critical, especially in a market where both are present.
Colors shown are illustrations. Real stones vary with lighting, origin, and quality. Natural alexandrite is rarely treated at all.
Properties
Hardness, toughness, and the one thing to watch
Alexandrite sits at 8.5 on the Mohs scale, harder than every gem in this guide except corundum and diamond. Tap or hover any number to compare.
Mohs measures scratch resistance, from talc (1) to diamond (10).
Hardness & wearability
At 8.5 on the Mohs scale, alexandrite is one of the hardest gemstones used in fine jewelry, second only to corundum (sapphire and ruby) and diamond. That hardness makes it highly resistant to everyday scratching.
The one thing to plan around is cleavage: chrysoberyl has a distinct cleavage plane in one direction, meaning a sharp, direct knock in the wrong spot can chip or split the stone even though its surface hardness is excellent. A protective setting and ordinary care keep this from ever being a practical concern.
Alexandrite's hardness is a genuine advantage over most colored gemstones - it just isn't a cleavage-proof one. Avoid sharp impacts, especially on a ring, the same way you would with any gem that has a cleavage direction.
Seeing the color change: light source matters
Alexandrite's color change isn't an enhancement - it's the mineral's own optical response to different light sources. Select a light source to see how the same stone looks under each.
Illustration: color shift by light source (schematic)
Light source
The 4Cs
Color change: evaluating two stones in one
Open each of the four Cs to see how alexandrite's color change, clarity, and cut fit together.
Evaluating alexandrite is fundamentally different from evaluating almost any other gemstone, because you are judging two colors and the transition between them. Fine alexandrite shows three critical characteristics: a strong green to bluish-green in daylight that is clean and saturated, not gray or muddy; a clear red to purplish-red under incandescent light, without brown or dull undertones; and a distinct and noticeable shift between the two, not a weak or partial change.
Stones that fail usually do so in predictable ways. Many show a weak green that leans toward gray, or a red that appears brownish. Others display only a slight shift, which significantly reduces value. The most valuable stones achieve what is often referred to as a complete color change, where the two appearances feel like entirely different gemstones.
Alexandrite typically forms with inclusions, so completely eye-clean stones are rare, especially in larger sizes. Minor inclusions are expected and accepted, as long as they do not interfere with the stone's color or transparency.
Alexandrite is strongly pleochroic, meaning it can show different colors depending on the viewing direction. This adds another layer of complexity beyond the standard color change. In rough form, the crystal may display multiple color directions simultaneously, including green, yellowish-green, and reddish tones. The cutter must decide how to orient the stone to maximize the most desirable outcome. A poorly oriented stone may weaken the color change or dilute one of the colors. A well-oriented stone aligns the dominant optical axis to enhance both the green and red phases as much as possible. This is one of the reasons fine alexandrite is so rare - even good rough material can be ruined by poor cutting decisions.
Cut plays a critical role in how the color change is perceived. A poorly cut stone may dilute the effect, making the transition appear weaker or uneven. A well-cut alexandrite enhances both colors and allows the shift to occur more cleanly across the entire surface. Because of its rarity, many stones are cut to preserve weight rather than optimize performance. This makes well-cut alexandrite significantly more valuable.
Pear
Oval
Cushion
Stones over one carat with strong color change are exceptionally rare, which is a major factor in their value. This is one of the few gemstones where carat weight and rarity accelerate together faster than almost anywhere else in colored stones - a clean, complete color change above one carat is a genuinely different tier of stone from the same quality under a carat, not just a bigger version of it.
Because fine material is so scarce at any size, alexandrite is typically bought and set small by design - it's one of the few gems where a modest carat weight is the norm for a fine stone, not a compromise.
Origins & Value
The Ural Mountains, and beyond
Original alexandrite was discovered in the Ural Mountains of Russia, and these stones are still considered the benchmark for quality.
Origin
Russia
- Known for
- The historic benchmark for quality
- Region
- Ural Mountains
- Material
- Extremely rare today, highly sought after
Original alexandrite was discovered in the Ural Mountains of Russia, and these stones are still considered the benchmark for quality. Russian material is extremely rare today and highly sought after.
Origin
Brazil
- Known for
- Strong color change
- Discovered
- A major modern source
- Character
- Among the best color change outside Russia
Modern sources include Brazil, Sri Lanka, and East Africa. Brazilian stones are known for producing strong color change.
Origin
Sri Lanka
- Known for
- Lighter, still attractive material
- Deposit type
- Alluvial
- Character
- Often lighter than Russian or Brazilian stones
Sri Lankan material often appears lighter, but can still be attractive.
Origin
East Africa
- Known for
- A modern, growing source
- Regions
- Tanzania and neighboring deposits
- Character
- Adds to the gem's limited modern supply
East Africa is also a modern source of alexandrite, alongside Brazil and Sri Lanka.
Regardless of origin, fine alexandrite is scarce.
Rarity and market value
Alexandrite's value comes down to how completely it changes color, and how clean each of its two colors is on its own. A strong green to bluish-green in daylight, a clear red to purplish-red under incandescent light, and a distinct, immediate shift between them together define a fine stone; weaker, grayer, or browner versions of either color - or a shift that's only partial - bring the value down sharply, regardless of size.
Clarity and cut both matter more here than in most colored gemstones: inclusions are expected and generally accepted, but a well-oriented, well-proportioned cut is what actually lets both colors perform, and stones cut to preserve carat weight instead often underperform stones that are smaller but better cut.
Origin carries real weight too, more than it does for some other colored gems - historic Russian material commands a genuine premium over Brazilian, Sri Lankan, or East African stones of comparable color, simply because so little of it exists. A laboratory report confirming natural origin and documenting the color change is standard for any alexandrite above a modest size.
Care
Wearing alexandrite every day
Alexandrite's hardness makes it one of the more forgiving fine gemstones to wear daily - the one thing to plan around is its single cleavage direction, not its surface durability.
Clean gently
Use lukewarm water, a drop of mild soap, and a soft brush, then rinse and pat dry.
Ultrasonic and steam are usually fine
Natural, untreated alexandrite's hardness and typical clarity generally tolerate both - check with your jeweler if a stone has unusual inclusions.
Avoid sharp, direct knocks
Chrysoberyl's single cleavage direction means a hard, pointed impact - not everyday wear - is the real risk, especially on a ring.
Choose a protective setting
A setting that shields the girdle and corners reduces the already-small risk from the cleavage direction.
Store pieces apart
Alexandrite's own hardness can scratch softer stones and jewelry metals, so keep pieces in separate pouches or a lined box.
Skip harsh chemicals
Chlorine and abrasive household cleaners dull the surface over time, as with any fine jewelry.
Shop the stone
Alexandrite jewelry, in stock now
Oval Cut Alexandrite & Diamond Ring
$18,000.00
Square Step Cut Fine Alexandrite From The Smithsonian Institute with Two Baguette Diamonds Ring
$17,000.00
Pear Cut Alexandrite & Diamond Dangle Earrings
$4,200.00
Cats Eye Alexandrite Ring With Diamonds
$5,350.00
Cats Eye Alexandrite & Diamond Studs
$3,800.00
Alexandrite & Diamond Dangles
$7,000.00
Shop
Alexandrite jewelry at Forever Rox Fine Jewelry
At Forever Rox Fine Jewelry, we focus on sourcing alexandrite that actually demonstrates what makes the gemstone special. A subtle shift is not enough - true alexandrite should clearly transform between lighting conditions, creating a piece that feels dynamic and alive.
FAQ
Alexandrite questions, answered
A strong shift from green in daylight to red under incandescent light with clear contrast.
Yes, especially in fine quality and larger sizes.
Chromium in the crystal structure alters how light is absorbed under different lighting conditions.
They are chemically real but not naturally formed, and they lack the rarity of natural stones.
Anything over one carat with strong color change is considered very rare.
High-quality natural alexandrite is highly collectible due to its rarity and unique properties.
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