Alexandrite: The Colour-Changing Gemstone Explained

Alexandrite is one of the rarest and most fascinating coloured gemstones. Under daylight or cool fluorescent lighting, a fine stone may appear green or bluish green. Move it beneath warmer incandescent light, and the same gemstone can become red, purplish red or reddish purple.

This dramatic transformation is known as the alexandrite effect. It is caused by the gemstone’s crystal chemistry and the different wavelengths produced by each light source—not by dye, electronic enhancement or a temporary surface treatment.

Natural alexandrite is exceptionally scarce, particularly when it combines a strong colour change, attractive colours in both lighting conditions, good clarity and a weight above one carat. Laboratory-created alexandrite offers a more accessible alternative, but buyers must distinguish genuine synthetic alexandrite from colour-changing sapphire, spinel, glass and other imitations.

Key Takeaways

• Alexandrite is the colour-changing variety of the mineral chrysoberyl.

• Fine alexandrite appears green to bluish green in daylight and red to purplish red under warm incandescent light.

• Chromium within its crystal structure is primarily responsible for the colour-change effect.

• Colour-change strength is the most important quality and value factor.

• Most natural faceted alexandrites weigh less than one carat.

• Fine stones above one carat rise sharply in value, while exceptional stones above five carats are extraordinarily rare.

• Natural alexandrite is usually untreated, although laboratory testing remains important.

• Lab-created alexandrite has essentially the same mineral composition and optical properties as natural material.

• Colour-change synthetic sapphire is an imitation rather than true alexandrite.

• Alexandrite measures 8.5 on the Mohs hardness scale and has excellent toughness, making it suitable for engagement rings.

• Mixed oval and cushion cuts are common because cutters must preserve weight and orient the stone for its strongest colour change.

• A significant natural alexandrite should be accompanied by an independent gemmological laboratory report.

Alexandrite at a Glance

GIA classifies alexandrite as the rare colour-changing variety of chrysoberyl and considers the strength and quality of its green-to-red transformation its most important quality factor.

What Is Alexandrite?

Alexandrite is a rare variety of chrysoberyl that displays a noticeable change of colour under different types of illumination. Ordinary chrysoberyl is generally yellow, yellowish green or brown. Material is classified as alexandrite when its composition and optical behaviour produce the characteristic colour-change effect.

The gemstone was discovered in Russia’s Ural Mountains during the early nineteenth century. Significant deposits were reported in 1830, and the gem was named in honour of Alexander II, who was then heir to the Russian throne. Its green and red colours also reflected the military colours of imperial Russia, helping the new gemstone acquire national and royal significance.

Alexandrite is sometimes described as “emerald by day and ruby by night”. This phrase communicates its general appearance, but alexandrite is chemically unrelated to both emerald and ruby:

• Emerald is a variety of beryl.

• Ruby is a variety of corundum.

• Alexandrite is a variety of chrysoberyl.

It is also important to distinguish alexandrite from any stone that merely changes colour. Colour-changing garnet, sapphire, spinel, fluorite and diaspore can all display variations under different lights, but they are separate minerals.

Why Does Alexandrite Change Colour?

Alexandrite changes colour because chromium replaces a small proportion of aluminium within the chrysoberyl crystal structure. This chromium selectively absorbs particular parts of visible light while transmitting others.

Daylight contains a relatively strong balance of blue and green wavelengths. Under daylight-equivalent illumination, the wavelengths transmitted by fine alexandrite usually make the stone appear green or bluish green.

Traditional incandescent lamps and candlelight contain a greater proportion of red wavelengths. Under these warmer sources, the transmitted red and purple components become more dominant, causing the gemstone to appear red, purplish red or reddish purple.

Colour Change vs Pleochroism

Alexandrite displays both colour change and pleochroism, but these are different optical effects.

Chrysoberyl is doubly refractive and strongly pleochroic. Alexandrite can display different basic colours along its crystallographic directions. A skilled cutter must orient the rough so that the finished gemstone shows its best combination of face-up colour and colour change through the crown.

Why the Effect May Look Different at Home

The colour change can vary according to:

• The colour temperature of the bulb

• The intensity of the light

• Whether daylight and artificial light are mixed

• The observer’s eyesight

• Surrounding wall and clothing colours

• The gemstone’s cut and orientation

• Camera processing and screen settings

Modern LED bulbs do not all reproduce the spectrum of traditional incandescent lamps. A stone may appear purple or grey under one warm LED and more distinctly red under another.

For consistent assessment, GIA uses approximately 6500 K daylight-equivalent lighting and approximately 2700 K incandescent-equivalent lighting when documenting colour-change gemstones.

What Colours Can Alexandrite Display?

The classic and most valuable change is from green or bluish green in daylight to red or purplish red under warm incandescent illumination. However, natural alexandrite can show a wider range of colours.

Possible Daylight Colours

• Bluish green

• Green

• Greenish blue

• Yellowish green

• Olive green

• Greyish green

• Brownish green

Possible Warm-Light Colours

• Red

• Purplish red

• Reddish purple

• Purple

• Violet

• Brownish red

• Greyish purple

• Orangish red

Fine alexandrite should display attractive colours in both lighting environments. A stone that shifts completely but changes from muddy olive green to greyish brown may be less valuable than one showing a slightly less complete change between vivid bluish green and purplish red.

GIA considers moderately strong to strong saturation desirable. Stones that are too pale lack intensity, while those that are excessively dark can appear almost black and lose brightness.

Understanding Colour-Change Percentage

Retailers sometimes describe alexandrite as showing a 70%, 90% or 100% colour change. There is no simple universal consumer grading system for assigning these percentages, so they should be treated as descriptive estimates rather than independently standardised grades.

Judge the physical stone or consistent videos rather than relying solely on a claimed percentage.

Where Is Natural Alexandrite Found?

Alexandrite was first associated with Russia’s Ural Mountains, where nineteenth-century deposits produced stones with vivid green-to-red colour change. Production from these historic Russian deposits is now very limited, and antique Russian examples continue to serve as an important quality benchmark.

Major and Historic Alexandrite Sources

Brazil became a major source during the twentieth century, particularly following discoveries in Minas Gerais. Fine Brazilian examples can rival historic Russian material and may combine strong colour change with greater clarity and size. Sri Lankan stones can reach larger sizes but often show yellowish-green, brownish-red or greyish-purple components.

Alexandrite has also been mined in Tanzania, India and Zimbabwe, sometimes as a by-product of emerald or other gemstone mining. GIA currently has established origin-determination data for stones from Russia, Brazil, Sri Lanka, Tanzania and India, while research on additional localities continues.

Does Origin Determine Quality?

No. Geographic origin can influence rarity, provenance and market demand, but it does not guarantee beauty.

A weak Russian stone is not automatically superior to an exceptional Brazilian, Tanzanian or Indian alexandrite. Colour-change strength, saturation, tone, clarity, cut and size should be evaluated before origin.

Origin should only be represented as confirmed when supported by an independent laboratory capable of making that determination. Visual appearance alone is not sufficient because deposits can produce overlapping characteristics.

Why Is Alexandrite So Rare?

Natural alexandrite requires an unusual geological environment capable of producing chrysoberyl while introducing enough chromium to create a visible colour change. Even when these conditions occur, much of the resulting material may be too dark, fractured, included or small for fine jewellery.

Its rarity is increased by several factors:

• Alexandrite is often recovered as a by-product rather than from mines dedicated solely to the gemstone.

• Production can be irregular and unpredictable.

• Only a portion of natural chrysoberyl displays a meaningful colour change.

• Strong green-to-red change is much less common than weak or muddy changes.

• Cutters must remove damaged material while preserving correct optical orientation.

• Most finished gemstones weigh less than one carat.

• Large stones with strong colour change and good clarity are exceptionally scarce.

GIA reports that attractive faceted alexandrites are usually below one carat and that prices rise dramatically as size and quality increase. Fine stones above five carats are particularly expensive and rarely available.

Supply is also difficult to standardise. Alexandrite may occur alongside emerald, corundum, cat’s-eye chrysoberyl and other minerals, which makes consistent commercial production challenging.

How to Judge Alexandrite Quality

Alexandrite does not have a universally adopted grading scale comparable with the diamond colour and clarity systems. GIA evaluates and identifies alexandrite but does not assign it a single overall grade. Buyers should therefore assess several interacting quality factors.

1. Colour-Change Strength

Colour change is the most important factor.

Look for:

• A clear visual difference between daylight and warm light

• Strong change across most of the gemstone

• Minimal muddy or grey areas

• Attractive colour in both lighting environments

• A response that remains visible without specialist equipment

The traditional quality ideal is bluish green or green in daylight and red to purplish red under incandescent light.

2. Colour Quality

The change itself is not enough. Both sets of colours should be appealing.

A stone may show:

• Strong change but unattractive brownish colours

• Excellent daylight green but weak warm-light colour

• Attractive red under warm light but dull olive in daylight

• Bright colour but incomplete change

• Full change but excessive darkness

The best gemstone offers a balanced combination rather than performing well in only one lighting condition.

3. Tone and Saturation

Tone describes how light or dark the colour appears. Saturation describes its strength or intensity.

Fine alexandrite usually has enough depth to appear rich without becoming blackish. Pale examples may lack impact, while very dark stones can hide both brilliance and colour change.

4. Clarity

Fine alexandrite commonly has better clarity than emerald. Eye-clean stones are especially desirable, although inclusions may be accepted when they do not reduce durability or distract from the colour.

Check for:

• Large central inclusions

• Surface-reaching fractures

• Chips around the girdle

• Cloudy areas

• Inclusions that interrupt the colour change

• Cavities beneath prongs

• Signs of fracture filling

Clean stones with strong colour change can command a substantial premium. Parallel needle-like inclusions may occasionally create chatoyancy, producing exceptionally rare cat’s-eye alexandrite.

5. Cut

Cut affects brightness, face-up colour, symmetry and the visibility of the colour change.

A well-cut alexandrite should have:

• A balanced outline

• Good symmetry

• Attractive brightness

• Limited windowing

• Limited extinction

• A secure girdle

• Correct orientation for the colour-change effect

• A face-up size appropriate to its carat weight

Mixed cuts with brilliant-style crowns and step-cut pavilions are common. Cutters frequently prioritise weight retention because the rough is so valuable, meaning some natural stones may have unusual proportions.

6. Carat Weight

Most natural faceted alexandrites weigh less than one carat. A fine-quality stone above one carat is considerably rarer, and value per carat can rise sharply as weight increases.

Do not choose carat weight alone. A smaller stone with vivid, balanced colour change may be more desirable than a larger gemstone that appears muddy, blackish or inactive.

Alexandrite Quality Checklist

Natural vs Lab-Created Alexandrite

Natural alexandrite develops through geological processes. Lab-created alexandrite is manufactured under controlled conditions but shares virtually the same chemical, optical and physical characteristics as natural chrysoberyl alexandrite.

Synthetic alexandrite has been produced using flux, Czochralski, floating-zone and other crystal-growth processes. Because it can be made with consistent colour and clarity, it is less rare and generally more affordable than equivalent natural material.

Lab-Created Alexandrite vs Alexandrite Simulants

Not every man-made colour-changing stone sold under an alexandrite-related name is true synthetic alexandrite.

Common imitations include:

• Colour-change synthetic sapphire

• Colour-change synthetic spinel

• Colour-change glass

• Colour-change garnet

• Coated or assembled stones

The term “alexandrite sapphire” generally refers to laboratory-grown colour-change sapphire. It is not chrysoberyl alexandrite and should not be priced or represented as such.

Which Option Is Better?

Natural alexandrite may be preferable for buyers who value:

• Geological rarity

• Historic provenance

• Collectability

• Natural inclusion patterns

• Long-term scarcity

• Independent origin documentation

Lab-created alexandrite may be preferable for buyers who want:

• A larger centre stone

• Strong colour change

• Greater apparent clarity

• A more accessible price

• Consistent matching stones

• The optical character of alexandrite without natural-stone rarity

Neither option should be misrepresented. The invoice and product description should clearly state whether the gemstone is natural, laboratory-created or an imitation.

Alexandrite Meaning and Symbolism

Alexandrite is associated with transformation, adaptability and balance because it changes between cool and warm colours. Its dual appearance makes it an appropriate symbol for different personalities, changing circumstances and two lives joining together.

The gemstone is also associated with:

• Good fortune

• Creativity

• Emotional balance

• Renewal

• Confidence

• Personal growth

• Hope

• Harmony between opposites

These meanings come from cultural tradition and modern gemstone symbolism rather than scientifically established effects.

Alexandrite is one of June’s birthstones, alongside pearl and moonstone. Its discovery and naming also connect it with imperial Russia and Alexander II.

For an engagement ring, its changing colour can represent a relationship remaining beautiful through different stages, surroundings and experiences.

Is Alexandrite Suitable for an Engagement Ring?

Alexandrite is highly suitable for an engagement ring when it is properly set and cared for.

It measures 8.5 on the Mohs hardness scale, making it more scratch-resistant than emerald, aquamarine, morganite and many other coloured gemstones. It also has excellent toughness and no cleavage, reducing its tendency to split along predetermined structural planes.

Alexandrite Durability Compared

Buyers comparing coloured centre stones with highly brilliant Moissanite Jewellery should understand the aesthetic difference. Moissanite is chosen primarily for brilliance and fire, whereas alexandrite is valued for rarity and colour transformation.

Alexandrite Is Particularly Suitable When

• The wearer wants a distinctive coloured gemstone.

• Daily-wear durability matters.

• The buyer values rarity over large visual size.

• A colour-changing stone has personal significance.

• The setting protects the gemstone appropriately.

• The ring can be removed for heavy manual activities.

Remove the Ring Before

• Weight training

• Contact sports

• Gardening

• Heavy cleaning

• DIY work

• Handling machinery

• Swimming

• Moving furniture

• Activities involving strong impact

Alexandrite is durable, but no gemstone is indestructible. A hard strike can still chip a facet edge, damage the girdle or bend the setting.

The Best Cuts, Settings and Metals for Alexandrite

The best design should display the colour change clearly, protect the gemstone and make efficient use of its natural size.

Best Alexandrite Cuts

Oval Cut

Oval mixed cuts are common because they retain weight efficiently and provide good surface area. Their curved outline has no vulnerable pointed corners.

Best for: solitaires, halos, vintage rings and three-stone settings.

Cushion Cut

Cushion cuts combine rounded corners with a square or rectangular outline. They can produce a rich, substantial appearance and suit both modern and antique-inspired designs.

Best for: halos, diamond shoulders and bespoke rings.

Round Cut

Round alexandrites can offer attractive brightness and symmetry, although more rough may need to be removed to create the shape.

Best for: classic solitaires and balanced halo designs.

Emerald or Step Cut

Step cuts emphasise colour and clarity rather than intense sparkle. They can work well with clean, strongly coloured material but may reveal windowing or inclusions more clearly.

Best for: Art Deco and architectural designs.

Pear or Marquise Cut

These elongated shapes create excellent finger coverage but contain points that require protective prongs.

Best for: distinctive solitaires and vintage-inspired rings.

Cabochon Cut

A cabochon may be used when inclusions produce chatoyancy. Cat’s-eye alexandrite must be cut with the correct dome and orientation to display its moving line of light.

Cut Comparison

Best Settings

Bezel Setting

A bezel surrounds the stone with a metal rim, providing excellent edge protection and a smooth everyday profile.

Halo Setting

A halo adds brightness and makes a naturally small alexandrite appear larger. Colourless accent stones also highlight the difference between its daylight and warm-light colours.

Six-Prong Setting

Six prongs provide additional security for oval or round stones while leaving much of the gemstone visible.

Four-Prong Setting

Four prongs create an open appearance but must be substantial and positioned carefully.

Three-Stone Setting

Diamond, sapphire or moissanite side stones can create contrast and increase the ring’s overall presence without requiring a larger alexandrite centre.

Best Metals

White metals can emphasise the cooler daylight colour, while yellow and rose gold can complement the warmer evening colour. The best choice should be made after viewing the actual stone against different metals.

How Much Is Alexandrite Worth?

Alexandrite value varies enormously. There is no dependable universal price per carat because two stones of identical weight can differ substantially in colour change, saturation, clarity, origin and cut.

Main Value Factors

• Strength of colour change
• Quality of both visible colours
• Saturation and tone
• Clarity
• Carat weight
• Cut and orientation
• Natural or laboratory-created origin
• Geographic origin
• Independent documentation
• Historic provenance

General Value Categories

Natural examples with weak or brownish colour change may sell for hundreds or low thousands per carat, while fine material with vivid change can reach many thousands or tens of thousands per carat. Exceptional large stones can command six- or seven-figure auction prices.

As one market benchmark, a 16.53-carat alexandrite and diamond ring reportedly sold at Sotheby’s for US$1.92 million, substantially above its estimate. Such exceptional auction results should not be used as standard retail pricing, but they demonstrate the premium attached to large, fine natural stones.

GIA confirms that most faceted alexandrites are below one carat and that value rises dramatically for larger stones with better quality.

Does Russian Origin Always Increase Value?

Documented Russian origin can add a substantial premium because nineteenth-century Ural material has historic prestige and limited supply. However, origin does not compensate for poor colour, low clarity or weak change.

An exceptional Brazilian stone can be more valuable than an unattractive Russian example. Always evaluate quality first and provenance second.

How to Identify and Buy Genuine Alexandrite

Natural and lab-created alexandrite cannot always be distinguished through visual inspection alone. Professional laboratories use microscopy, spectroscopy, trace-element analysis and other testing methods to identify the material and, where possible, determine origin.

Warning Signs

Be cautious when:

• A large “natural” stone is surprisingly inexpensive.

• The seller provides no laboratory report.

• The colour change appears unnaturally perfect.

• The item is described as “alexandrite sapphire”.

• The seller avoids stating whether it is natural or synthetic.

• Only one heavily edited photograph is provided.

• The origin is guaranteed without supporting documentation.

• The invoice simply says “colour-changing stone”.

• A certificate comes from an unknown in-house laboratory.

• The seller uses “created”, “cultured” or “simulated” interchangeably.

GIA warns that an inexpensive gemstone showing a strong red-to-green change is likely to be synthetic or an imitation rather than fine natural alexandrite.

How to Examine Colour Change

Ask to view the gemstone:

• In indirect natural daylight
• Under daylight-equivalent lighting
• Beneath a warm incandescent-equivalent source
• In mixed everyday lighting
• Away from jewellery-counter spotlights
• Against a neutral grey or white background
• Beside another alexandrite for comparison

Request separate, unedited videos under both lighting conditions. The camera should remain in a consistent position, with the light source changed rather than the gemstone moved to a completely different environment.

Ask for an Independent Laboratory Report

A reputable coloured-stone report may provide:

• Natural or laboratory-grown identification

• Mineral and variety

• Measurements

• Carat weight

• Shape and cutting style

• Colour description

• Detectable treatments

• Geographic-origin opinion when requested and possible

• Report number and verification details

GIA evaluates alexandrite but does not give it an overall quality grade. Its coloured-stone report can identify whether a specimen is natural or laboratory-grown, describe its basic characteristics, disclose detectable treatment and offer an origin opinion where possible.

Essential Questions to Ask

• Is the stone natural or laboratory-created?

• Is it chrysoberyl alexandrite or a colour-change simulant?

• Has it received any treatment?

• How strong is the colour change?

• What colours appear under each light source?

• Is the colour-change percentage independently measured?

• Is there an independent report?

• Can the report be verified online?

• Is geographic origin confirmed or only assumed?

• What is the exact carat weight?

• Are there any surface-reaching fractures?

• Can I view unedited videos?

• What is the return period?

• Does resizing affect the return policy?

• Is an insurance valuation available?

Do Not Use Destructive Home Tests

Avoid scratch testing, heating, chemical exposure or attempting to remove the gemstone from its setting. These methods can damage the stone and still fail to prove its identity.

How to Clean and Care for Alexandrite Jewellery

Alexandrite is durable and stable under normal wearing conditions. Warm soapy water is always considered safe, while steam and ultrasonic cleaning are generally acceptable for untreated stones without significant fractures. However, fracture-filled material should only be cleaned gently with warm soapy water.

Safe Home Cleaning Method

• Fill a bowl with lukewarm water.
• Add a small amount of mild washing-up liquid.
• Allow the jewellery to soak briefly.
• Clean around the setting using a soft toothbrush.
• Rinse carefully with clean lukewarm water.
• Pat dry with a lint-free cloth.
• Allow the jewellery to dry completely before storage.

When to Avoid Ultrasonic or Steam Cleaning

Use only gentle hand cleaning when:

• The stone contains significant fractures.

• Fracture filling has been detected.

• The treatment status is unknown.

• The setting contains other delicate gemstones.

• The ring is antique.

• The mount is damaged.

• A gemstone is loose.

• The jeweller has advised against mechanical cleaning.

Although alexandrite is usually untreated, detectable treatments should be stated in a reputable laboratory report.

Storage Guidance

• Keep alexandrite in a lined jewellery box.

• Store it separately from diamonds, rubies, sapphires and moissanite.

• Avoid loose storage in handbags or drawers.

• Keep chains fastened to prevent tangling.

• Store laboratory reports separately from the jewellery.

• Do not leave valuable pieces beside sinks or wrapped in tissue.

Professional Maintenance

Have regularly worn alexandrite rings inspected periodically for:

• Loose prongs

• Worn bezel edges

• Chips around the girdle

• Bent bands

• Loose accent stones

• Damaged claws

• Changes in the setting’s alignment

Arrange an immediate inspection after a hard impact, even when no damage is visible.

Final Alexandrite Buying Checklist

Before purchasing, confirm that:

• The gemstone is clearly identified as natural or laboratory-created.

• It is chrysoberyl alexandrite rather than colour-change sapphire.

• The colour change is visible under realistic lighting.

• Both colour states are attractive.

• The stone is not excessively dark.

• Clarity is suitable for the price.

• The cut displays the change across the face.

• Carat weight and dimensions are stated.

• Detectable treatments have been disclosed.

• Significant natural stones have independent reports.

• Origin claims are supported by evidence.

• The report number can be verified.

• The setting protects vulnerable edges.

• The precious metal is accurately described.

• Returns, resizing and warranty conditions are provided in writing.

• Care instructions are clear.

• Insurance has been considered for a high-value stone.

Conclusion

Alexandrite is extraordinary because its beauty depends on changing light. A fine natural gemstone can shift from green or bluish green during the day to red or purplish red beneath warmer evening illumination, creating two distinct appearances within one stone.

Its value depends primarily on the strength and quality of that transformation. Clarity, cut, carat weight, natural origin and documented provenance also matter, but a large stone with dull colours should not be preferred over a smaller example with vivid, balanced change.

Buyers considering an alexandrite design from Franc Laurent should view the stone under at least two controlled light sources and request clear written identification. For a significant natural gemstone, an independent laboratory report is essential. With the right documentation, setting and care, alexandrite can become a durable and highly individual piece of fine jewellery.