Imagine buying a gemstone that looks green in daylight, but when looking at the same stone indoors under warm lighting it has changed to appear red or purple.
Nothing has been done to the gemstone to change its color; the lighting has.
This is what makes alexandrite one of the most interesting change of color gemstones in the world.
Alexandrite is a rare variety of the mineral chrysoberyl which exhibits unusual interactions with different light sources.
It has the wonderful capability of appearing green to bluish green in daylight or under fluorescent light and red, purplish red, or raspberry-colored when exposed to incandescent light.
The effect is not magical or due to reflection, but a combination of chemistry and the absorption of certain wavelengths of visible light.
What Is Alexandrite?
Alexandrite belongs to the mineral family called chrysoberyl.
Ordinary chrysoberyl can be found in yellow, green, or brown colors, but Alexandrite is the color changing variety.
This variety owes its unusual optical properties to traces of chromium within its crystal structure.
The chemistry of the mineral causes it to change its apparent color depending on which light illuminates it.
Green in daylight and red in incandescent light.
However, real gems can be more complicated than this.
Depending on the stone and the lighting, it may appear blue-green, olive green, teal, purple, raspberry, reddish purple, or brownish red.
The degree to which its colors change can also vary significantly from stone to stone.
Why Does Alexandrite Change Color?
Alexandrite changes color because it absorbs some wavelengths of visible light more strongly than others.
Chromium plays a large part in this.
Different light sources have different mixtures of wavelengths.
Daylight tends to have a relatively broad spectrum of wavelengths and can cause alexandrite to appear green or blue-green.
Traditional incandescent lighting has more wavelengths of red light and can cause alexandrite to appear reddish, purple, or raspberry-colored.
So alexandrite is not physically transforming itself when the lighting changes-the gemstone stays the same.
The mixture of wavelengths of the light interacting with it has changed, which changes the color our eyes see.
Does Alexandrite Actually Change Color?
Yes, but it is important to understand what this means.
Alexandrite is not like an electronic display that has been programmed to change from one specific color to another instantly.
It reacts to its environment, and as you move from one lighting condition to another, the wavelengths of light interacting with it will change, and its appearance will change with them.
Mixed lighting can cause an intermediate appearance.
Thus, alexandrite can sometimes appear to have multiple colors, not just green or red.
What Colors Can Alexandrite Show?
The classic appearance is a strong transition between green and red colors.
However, natural alexandrite can exhibit a much broader range of colors.
In daylight or under cool lighting, it might look:
- Green
- Bluish green
- Teal
- Olive green
While under warmer lighting it might look:
- Red
- Purplish red
- Raspberry
- Reddish purple
- Brownish red
The exact colors depend on the gemstone, its chromium content, cut, saturation, and the light source.
Do All Alexandrites Change Color Equally?
No.
This is one of the most important things to realize when comparing alexandrite.
Some stones show a dramatic transformation between two distinctly different colors while others only show a moderate shift.
A gemstone might move from blue-green to strong purple while another gem moves from olive green to brownish red.
The strength and attractiveness of the color change can greatly influence its desirability and value.
What Makes a Good Color Change?
Gemologists consider the quality of the colors and the degree of change between them.
A good strong change means the gemstone looks distinctly different under different lighting, not just a slightly warmer or cooler shade of the same color.
For example:
Green → red
is a more dramatic color change than:
Greenish blue → slightly greener blue.
The quality of each individual color also matters.
A strong change between two muddy or brownish colors might be less desirable than an attractive transition between vivid green and raspberry red.
Is Alexandrite Rare?
Fine natural alexandrite is rare.
The gemstone was first discovered in Russia’s Ural mountains in the 19th century, and historically important Russian material was famous for its green to red color change.
Alexandrite has since been found in other places including Brazil, Sri Lanka, and parts of Africa.
However, fine stones with attractive colors, good transparency, a useful size, and a strong color change are still rare.
This is one reason high-quality natural alexandrite can come with such a high price tag.
Is Alexandrite Good for Rings?
Yes.
Not only is alexandrite visually remarkable, but it’s also relatively durable.
Chrysoberyl ranks approximately 8.5 on the Mohs hardness scale, and alexandrite has a good scratch resistance for a colored gemstone.
The Gemological Institute of America classifies alexandrite as a rare color-changing variety of chrysoberyl and gives more information on its color, history, sources, and quality in its GIA guide to alexandrite.
Hardness and its unusual optical properties make alexandrite a particularly interesting choice for an engagement ring or other piece of jewelry that is likely to be worn frequently.
Why Does Alexandrite Work Well in Engagement Rings?
Most engagement-ring gemstones are chosen for a relatively consistent appearance.
Alexandrite does almost the reverse of this.
Its appearance can change throughout the day depending on its environment.
Outside, the stone might look green or bluish green.
At dinner under warm lighting, it might look purple or reddish.
Under mixed modern LED lighting, it might fall somewhere between these colors.
For someone with an alexandrite ring, that changing appearance can be the central design feature, and not a flaw to be hidden.
The ring literally has different personalities depending on its environment.
Natural vs. Lab-Grown Alexandrite
Both natural and laboratory-grown alexandrite exist.
Natural alexandrite forms naturally while laboratory-grown alexandrite is created in a controlled environment.
Natural fine-quality alexandrite is rare, and it is uncommon to find stones with desirable colors, good transparency, a useful size, and a strong color change.
Lab-grown alexandrite can reproduce the chemical and optical characteristics of natural alexandrite.
Because natural high-quality alexandrite is scarce, laboratory-grown material can offer the same desirable viewing experience at a significantly lower price.
The important issue is disclosure.
A buyer should know whether the gemstone is natural or laboratory-grown before purchasing it.
Alexandrite vs. Color-Changing Sapphire
Alexandrite isn’t the only gemstone capable of changing color.
Some sapphires, garnets, and other gemstones can also exhibit color changes.
However, alexandrite is so strongly associated with the phenomenon that the phrase “alexandrite effect” is sometimes used to more generally describe dramatic changes in the color of other gemstones under different illumination.
The gemstones are nevertheless different minerals.
Alexandrite is chrysoberyl while sapphire is corundum, and they should not be considered interchangeable simply because they both can show color change.
How Does Lighting Affect Alexandrite?
Lighting is extremely important when considering this gemstone.
A photograph of this gemstone under one type of lighting only tells part the story.
Ideally, the gemstone should be viewed under several conditions of lighting including:
Natural daylight
Cool or daylight-balanced artificial light
Warm artificial light
The differences can be significant.
Modern LEDs can also vary significantly in their spectral output and color temperature, so alexandrite might not always behave as expected simply because a bulb is labeled as “warm”.
This is another reason why videos and several photographs can be particularly helpful when buying alexandrite online.
Does Alexandrite Look Different in Photographs?
It can.
Cameras, white balance, exposure, screen settings, and lighting can all affect the way a photograph looks.
A phone may process the image differently than your eye will see it, and two different screens may display the photograph differently.
For a gemstone that is a color-change gemstone, this becomes an even more important concern because the entire appeal of the stone depends on how it responds to light.
When evaluating alexandrite from a distance, ask for images or video under clearly identified lighting conditions if possible.
What Determines Alexandrite’s Value?
Several factors come into play when determining a price for alexandrite.
Color Change
A strong and clearly visible change is highly desired.
Color Quality
The individual colors should also be attractive, rather than overly dark or muddy.
Clarity
Transparent stones with fewer distracting inclusions are generally more desirable, although natural inclusions can also be desirable.
Size
Fine natural alexandrite is more rare as the carat weight increases.
Cut
Good cutting helps display both the gemstone’s color and its brightness.
Origin
Origin can greatly affect market interest, especially for historically important Russian material, but it should not replace examining the actual gemstone.
The most expensive alexandrite therefore isn’t simply the largest stone.
It is usually a combination of rarity, color, change, clarity, and size.
Is Alexandrite Always Green and Red?
No.
“Emerald by day, ruby by night” is a useful traditional description, but real alexandrite often displays more nuanced colors.
A stone might be teal in daylight and purple under warm light and another stone might shift from olive green to raspberry.
Another might show blue-green and reddish purple.
Expecting every single piece of alexandrite to display pure emerald green and pure ruby red can lead to many unrealistic expectations.
The important characteristic is a meaningful color change, not a conformity to two exact color names.
How Should You Choose Alexandrite?
Start with the color change.
Ask to see the gemstone under more than one light source and then evaluate whether you actually like both sides of the stone.
This matters.
If you love its daylight green but dislike its indoor purple, the novelty of the color change may not be worth seeing a color that you dislike every evening.
Next, consider:
Natural or lab-grown origin
Strength of color change
Daylight color
Warm-light color
Clarity
Cut
Carat size
Setting
Budget
Alexandrite should be chosen as a complete visual experience rather than carat weight only.
Which Metal Looks Best With Alexandrite?
There is no single answer because alexandrite can show several colors.
White gold and platinum create a relatively neutral frame.
Yellow gold brings warmth and can emphasize the warmer side of the gemstone.
Rose gold can interact particularly strongly with purple, raspberry, and reddish tones.
The choice depends partially on which side of the color change the wearer wants the setting to emphasize.
Accent stones can also affect the result.
Small diamonds around alexandrite can create contrast while allowing the changing center stone to remain the focal point.
How Should You Care for an Alexandrite Ring?
Alexandrite’s hardness makes it a good candidate for frequent wear, but it isn’t indestructible.
Avoid strong impacts.
Remove fine jewelry during weightlifting, heavy manual work, or any situation when the setting might be damaged.
Routine cleaning can generally be accomplished with warm water, mild soap, and a soft brush assuming the specific stone and setting don’t require any specialized care.
For valuable natural alexandrite, periodic professional inspection of the setting is also wise.
Frequently Asked Questions
Why does alexandrite change from green to red?
Chromium within alexandrite selectively absorbs wavelengths of visible light.
Because daylight and warm artificial light contain different spectral distributions, different colors become dominant to the human eye.
Is alexandrite naturally color-changing?
Yes.
Natural alexandrite’s color-changing effect is an optical property of the gemstone related to its chemical composition and interaction with different light sources.
Does all alexandrite change color?
Color change defines alexandrite, but the strength and quality of the effect varies significantly between stones.
Is alexandrite rarer than diamond?
Fine natural alexandrite with strong color change, good clarity, and significant size is extremely rare.
Direct rarity comparisons with diamonds depend on the quality and type of stones being compared.
Is lab-grown alexandrite real alexandrite?
Laboratory grown alexandrite can have the same basic mineral composition and color-changing mechanism as natural alexandrite, but its origin is different and should be clearly disclosed.
Is alexandrite durable enough for an engagement ring?
Yes.
Alexandrite has a Mohs hardness of approximately 8.5 and is considered a durable colored gemstone, although reasonable care and a secure setting are still important.
Final Thoughts
Alexandrite changes color because its chemistry interacts differently with the spectrum of different light sources.
Chromium within the chrysoberyl crystal helps create the effect as daylight can emphasize green or blue-green wavelengths while warmer artificial light can bring forward red, purple, or raspberry tones.
The gemstone itself hasn’t transformed.
The light illuminating it has.
This simple scientific explanation creates one of the more unusual visual effects found in fine jewelry.
And it also explains why alexandrite shouldn’t be chosen from a single photograph.
To understand the stone, you need to see both sides of its personality-the color it shows in daylight and the color waiting to appear when the light changes.
