Alexandrite is a color-change variety of the mineral chrysoberyl. Green in daylight. Red under incandescent light. One stone. Two completely different appearances.

That phenomenon alone makes it one of the most extraordinary gems on earth. But alexandrite is also one of the most misrepresented. The vast majority of stones sold online as “alexandrite” are lab-grown or outright simulants. Fine natural material, especially from Russia, is genuinely scarce and commands prices that rival top rubies and sapphires.

This guide covers everything collectors and professionals need to know: the science, the origins, the market, and how to avoid getting burned.

The alexandrite definition trips up even experienced buyers. It is not a sapphire variant. It is not related to emerald. It belongs to the chrysoberyl family, a distinct mineral group that includes cat's-eye chrysoberyl and yellow chrysoberyl, but shares nothing chemically with corundum (ruby, sapphire) or beryl (emerald, aquamarine).

The alexandrite mineral formula is beryllium aluminum oxide: BeAl₂O₄. In its pure form, chrysoberyl is colorless to yellow-green. Alexandrite forms when trace amounts of chromium substitute for aluminum in the crystal lattice during formation.

Chromium is the same element responsible for the red of ruby and the green of emerald. In alexandrite, it creates a narrow transmission window in the visible spectrum, centered around 580 nm, that sits precisely at the boundary between green and red. The light source determines which side of that boundary dominates.

Alexandrite scores 8.5 on the Mohs scale. That places it above spinel (8) and below corundum (9). It is harder than most gems in circulation and has no cleavage planes that would make it prone to splitting. For a collector's stone, that durability is a genuine asset.

The alexandrite luster is vitreous, glass-like, with a refractive index of 1.746 to 1.755. That refractive index is higher than spinel and tourmaline, contributing to the stone's sharp, lively appearance.

Several gems change color. None do it with the same drama or rarity as alexandrite.

What sets alexandrite apart is the completeness of the shift, from a clean green to a saturated red, combined with its hardness, rarity, and documented history. No other gem does all three simultaneously. See also our What Is Spinel guide.

In natural daylight or fluorescent light (which is rich in blue-green wavelengths), alexandrite appears green to bluish-green. Move it under a tungsten incandescent bulb or candlelight (which is rich in red wavelengths), and it shifts to red to purplish-red.

This is not an optical illusion. It is a physical response to the spectral composition of the light source.

Chromium absorbs light across most of the visible spectrum, but leaves two transmission windows open: one in the green (~540 nm) and one in the red (~680 nm). In daylight, which contains more blue and green energy, the green window dominates. Under incandescent light, which is weighted toward red and yellow, the red window takes over.

The 580 nm absorption band is the critical threshold. Alexandrite sits right on it. That is why the color change is so complete, and why no other gem replicates it with the same fidelity.

The trade grades color change on a four-point scale:

Most natural alexandrite on the market shows moderate change. Very strong change, especially in stones above 1 carat, is genuinely uncommon.

The phrase is marketing shorthand, but it captures the ideal. A top alexandrite should look like a fine emerald in daylight, pure green, not gray or brownish, and like a fine ruby under incandescent light, red, not pink or purple.

Stones that achieve both benchmarks simultaneously are extraordinarily rare. Most natural alexandrite leans toward one end: either the green is strong but the red is dull, or vice versa. A stone that nails both is a collector-grade specimen.

Alexandrite was first discovered in Russia's Ural Mountains in 1830, reportedly on the birthday of future Tsar Alexander II, hence the name. The Malysheva mine in the Urals produced the stones that set the standard: vivid green in daylight, deep red under incandescent light, with exceptional clarity.

Russian alexandrite deposits are now effectively exhausted. Commercial mining ceased decades ago. Russian alexandrites that appear at auction come from old collections or estates, not active production. That scarcity is structural and permanent.

Brazil's Hematita mine, discovered in the 1980s, became the primary commercial source of alexandrite. Brazilian material is generally larger, stones above 5 carats are more common than from Russia, but the color change is typically less complete.

Brazilian alexandrite often shows a more yellowish-green in daylight and a brownish-red under incandescent light. Fine Brazilian material with strong color change exists and is commercially significant, but it rarely matches the chromatic purity of top Russian stones.

Sri Lanka produces alexandrite as a byproduct of sapphire mining. Stones tend to be included and show moderate color change. Larger sizes occur but fine material is uncommon.

India (Andhra Pradesh) has been a notable source since the 1980s. Indian alexandrite can show strong color change, and some material rivals Brazilian quality. The Andhra Pradesh deposits have produced stones with distinctive inclusion patterns useful for origin determination.

Tanzania and Madagascar produce smaller quantities. Tanzanian material can show attractive color change but is rarely seen in significant sizes. Madagascar stones are variable in quality.

Origin matters enormously in this market. A GIA or Gübelin report confirming Russian origin adds a substantial premium, often 2x to 5x the price of comparable Brazilian material. The premium reflects both rarity and historical prestige.

For collectors: origin determination requires laboratory analysis. Visual identification of Russian alexandrite is not reliable. Inclusions can suggest origin, but only spectroscopic analysis and comparison with reference databases provides a defensible conclusion.

This is the central problem in the alexandrite market. Most stones sold as “alexandrite” online, especially at prices under $500, are not natural. Many are not even true synthetic alexandrite. They are simulants.

True synthetic alexandrite has the same chemical composition as natural alexandrite. It is grown in a laboratory using one of two methods:

Lab-grown alexandrite is not a fraud if disclosed. It is priced at $50–$500 per carat, a fraction of natural material. The problem is when it is sold without disclosure, or misrepresented as natural.

Simulants are different materials that mimic alexandrite's appearance:

The vanadium glass problem is pervasive on Etsy, Amazon, and wholesale platforms. Listings often use the word “alexandrite” without qualification.

Three practical tests:

Alexandrite is one of the few major colored gems where treatment is the exception, not the rule. Most natural alexandrite is sold untreated. That is a significant advantage in a market where heated rubies and fracture-filled emeralds are the norm.

Fracture filling, injecting a resin or glass into surface-reaching fractures to improve apparent clarity, does occur in alexandrite, though it is uncommon. A stone with suspicious clarity for its price tier warrants scrutiny.

Heat treatment, which is standard for sapphire and ruby, does not significantly improve alexandrite's color. The chromium content that drives the color change is intrinsic to the crystal structure, it cannot be enhanced by heat. As a result, the vast majority of natural alexandrite is unheated, and this is the baseline expectation, not a premium attribute.

For collectors, this simplifies due diligence. The primary treatment concern is fracture filling, not heat.

The three laboratories that carry weight in the collector market:

For any stone above $5,000, a laboratory report is not optional. For Russian-origin claims specifically, a Gübelin or SSEF report carries the most authority.

The first test is free: use two light sources.

Hold the stone under daylight or a daylight-equivalent LED. Note the color. Then hold it under an incandescent bulb or a penlight. If the color does not shift clearly, it is either a weak stone or not alexandrite at all.

The alexandrite luster should be vitreous and sharp. Dull or waxy surfaces suggest glass or low-quality material.

Under 10x magnification, natural alexandrite inclusions include:

Flux-grown synthetics show curved growth lines and flux inclusions (wispy veil-like features). Hydrothermal synthetics are cleaner and require advanced testing. Glass shows gas bubbles and swirl marks.

A full laboratory report on alexandrite covers:

For Russian alexandrite specifically, origin determination is the critical line item. Without it, a “Russian alexandrite” claim is unverifiable.

Brazilian alexandrite at fine quality trades at roughly $2,000–$12,000 per carat for attractive stones, and $10,000–$50,000+ for top-tier pieces. Russian material starts at $5,000–$15,000 per carat for smaller fine stones and climbs steeply with size and color-change strength.

Most cut gems weigh under 1 carat. Stones above 3 carats with strong color change are rare regardless of origin. Above 5 carats with confirmed Russian origin: genuinely exceptional.

December 2024, Sotheby's Magnificent Jewels, New York: a ring set with a 16.53-carat oval alexandrite sold for $1.9 million, approximately $115,000 per carat, setting a world auction record for alexandrite. The same sale offered a pair of alexandrite earrings (7.69 ct + 7.38 ct) that sold for $1.2 million after a four-minute bidding war. Three alexandrite lots combined for $3.3 million total.

Sotheby's specialist Anna Ruzhnikov called the stones “the finest and largest alexandrites the house has ever encountered” and noted a “notable surge” in collector interest, with buyers now placing alexandrite “on par with legendary sapphires, emeralds, and rubies.”

The factors that drive auction premiums are consistent: size above 5 carats, very strong color change, confirmed Russian origin, clean clarity, and no treatment.

The Ural Mountain deposits are exhausted. Brazil's Hematita mine is producing less material than it did in the 1990s and 2000s. New sources, Tanzania, Madagascar, India, produce smaller quantities and rarely match the color-change quality of the benchmark origins.

Supply is structurally declining. Collector demand is rising. The December 2024 auction results, stones selling at 3x their high estimates, reflect that imbalance directly.

For collectors: the window to acquire fine natural alexandrite at current prices may not remain open indefinitely. The category is moving from specialist interest to mainstream collector awareness. That transition typically compresses the window for value acquisition.

What is alexandrite stone? Alexandrite is a rare color-change variety of the mineral chrysoberyl (BeAl₂O₄), appearing green in daylight and red under incandescent light due to trace chromium in its crystal structure. It was first discovered in Russia's Ural Mountains in 1830 and is now found in Brazil, Sri Lanka, India, Tanzania, and Madagascar.

Is alexandrite a mineral? Alexandrite is a variety of the mineral chrysoberyl, not a distinct mineral species itself. The classification is: mineral class, oxides; species, chrysoberyl; variety, alexandrite. The color-change property distinguishes it from other chrysoberyl varieties.

Is alexandrite a precious stone? The traditional “precious stone” category (diamond, ruby, emerald, sapphire) is a historical trade classification, not a scientific one. Whether alexandrite is a precious stone depends on who you ask. In practice, fine natural alexandrite commands prices that exceed most rubies and sapphires on a per-carat basis. The collector market treats it as a top-tier gem. The classification matters less than the price reality.

Where is alexandrite found? Alexandrite is found in Russia (Ural Mountains, the original and now exhausted source), Brazil (Minas Gerais state, Hematita mine), Sri Lanka, India (Andhra Pradesh), Tanzania, and Madagascar. Russian material remains the benchmark for quality and commands the highest prices. Brazil is the current primary commercial source.

What does an alexandrite stone look like? In daylight, fine alexandrite looks like a vivid green gem, comparable to a good emerald. Under incandescent light, it shifts to red or purplish-red, comparable to a ruby. The intermediate zone, visible in mixed lighting, often shows a brownish or grayish transition. The luster is vitreous and sharp. Most cut stones weigh under 1 carat; larger stones are uncommon.