Is chrysoberyl the same as alexandrite?
No: alexandrite is the colour-change variety of chrysoberyl, BeAl2O4, hardness 8.5. Every alexandrite is chrysoberyl, not the reverse. Three questions decide.
No. Chrysoberyl is the mineral species, BeAl2O4, hardness 8.5, density 3.75; alexandrite is its rare colour-change variety, green in daylight and red in incandescent light, in GIA's words. Every alexandrite is chrysoberyl, but plain yellow, green or brown chrysoberyl is not alexandrite, and the September 2026 IMA list has no alexandrite row.
In short
- One is a species, the other a variety of it. The IMA-CNMNC list of minerals (September 2026) lists chrysoberyl, BeAl2O4, grandfathered, 1789, Brazil. A script over the list finds no row named alexandrite. GIA calls alexandrite a rare variety of the mineral chrysoberyl, so the relationship runs one way: all alexandrite is chrysoberyl, but chrysoberyl in the sheet’s greens, yellows and browns that does not change colour is not alexandrite.
- The three-question rule. Is it chrysoberyl? Does it change from green in daylight to red in incandescent light? Is it natural? Three yeses make natural alexandrite. A no to the second leaves chrysoberyl. A no to the third makes synthetic alexandrite, which the International Gem Society calls real alexandrite but not a natural gemstone. A no to the first means it is not alexandrite at all.
- Chromium is the difference. The Handbook of Mineralogy sheet says chrysoberyl may be raspberry-red under incandescent light when chromian; the IGS writes alexandrite’s formula as BeAl2O4 + Cr and says beryllium and chromium rarely occur in the same rocks. GIA says the change comes from the way the mineral absorbs light, not from its pleochroism.
- Documented failure: the refractometer. GIA gives alexandrite, ruby and sapphire the same birefringence, 0.008 to 0.010. On GIA’s indices alexandrite (1.746 to 1.755) sits 0.007 below corundum (1.762 to 1.770); on the Handbook sheets the gap is 0.003; on the IGS figure for Ural alexandrite, 1.759, it closes to nothing against the corundum sheet’s lowest value. Synthetic corundum is the simulant the IGS names.
- Colour change alone is not alexandrite. GIA describes colour-change sapphire, most often blue in daylight and purple in incandescent light, and says other gems also change colour with the light source. The IGS adds that not every colour-change chrysoberyl is an alexandrite, and that no gemmological consensus fixes where the line falls.
| Material | IMA species | Change, daylight to incandescent | Alexandrite? | Natural? | Source | What separates it |
|---|---|---|---|---|---|---|
| Natural alexandrite | Chrysoberyl, BeAl2O4 | Green or bluish green to brownish or purplish red | Yes | Yes | GIA; Handbook (chromian) | All three questions answered yes |
| Synthetic (lab-created) alexandrite | Same composition as chrysoberyl; made, not a mineral | Yes | Yes, but not natural (IGS) | No | IGS: since the 1960s | Laboratory only: curved striae, bubbles, platinum or seed inclusions (IGS) |
| Colour-change chrysoberyl outside the classic shift | Chrysoberyl | Yes, other colour pairs | Not always (IGS); no agreed line | Yes | IGS | Judgement on the colour pair; no consensus boundary |
| Chrysoberyl without a colour change | Chrysoberyl | No | No | Yes | Handbook: greens, yellows, browns | Question 2 |
| Cat’s-eye chrysoberyl | Chrysoberyl | Not as such; GIA notes cat’s-eye alexandrite exists | Only if it also changes colour | Yes | Handbook; GIA; IGS | Chatoyancy is a separate effect |
| Synthetic corundum with an alexandrite-like change | Corundum composition, Al2O3; made, not a mineral | Yes | No | No | IGS | Question 1: not chrysoberyl; the corundum sheet gives uniaxial, indices 1.759 to 1.772 |
| Colour-change sapphire | Corundum, Al2O3 | Most often blue to purple | No | Yes, as GIA describes it | GIA | Question 1, and the colour pair |
Is chrysoberyl the same as alexandrite? The criteria
Two kinds of name. The IMA list is, in its own heading, a list of valid mineral species; chrysoberyl is one of them. Alexandrite is a variety name: a colour form of one species with a trade and gemmological meaning, but no row. The same relationship holds for peridot and olivine, and for emerald and beryl, set out on is olivine the same as peridot and is dioptase the same as emerald.
The criteria that decide a label, in order: the species, from composition and optics; the colour change, between daylight and incandescent light; and origin, natural or laboratory-grown. The Handbook of Mineralogy chrysoberyl sheet supplies the species numbers: BeAl2O4, orthorhombic, hardness 8.5, measured density 3.75, indices α 1.746, β 1.748, γ 1.756, pleochroic X red, Y yellow-orange, Z emerald-green. GIA’s alexandrite figures fall inside them: indices 1.746 to 1.755, specific gravity 3.73, hardness 8.5.
What this page does not repeat. How to tell chrysoberyl from topaz and corundum by hardness, weight and index, and why weighing fails on a cut stone, is the two-bracket rule on chrysoberyl. That chrysoberyl is not a beryl is answered there too. The identification guides are indexed at the collecting guides.
The three-question rule for an alexandrite label
Three questions, each with a source.
- Is it chrysoberyl? If not, it is not alexandrite, whatever it does under a lamp. The IGS names synthetic corundum with an alexandrite-like colour change as a simulant; GIA describes colour-change sapphire.
- Does it change from green to red? GIA: green in daylight or fluorescent light, brownish or purplish red in the incandescent light of a lamp or candle flame. The IGS says graders take natural sunlight as the baseline, so the classic change is green in sunlight and red in incandescent light. No change: chrysoberyl, not alexandrite. A change to other colours: colour-change chrysoberyl, which the IGS says is not always called alexandrite.
- Is it natural? The IGS says synthetic alexandrite has been made since the 1960s by melt, hydrothermal and flux methods, with properties identical to natural stones, and that gemmologists can sometimes identify it by inclusions: curved striae, bubbles and liquid inclusions, or platinum and seed material.
The finish state is one of four labels: natural alexandrite; synthetic alexandrite; chrysoberyl, with or without a colour change; or not chrysoberyl. Question 2 needs two light sources; questions 1 and 3, on a cut stone, need a gemmologist. The IGS says a professional gemological laboratory can make the determination, and this page gives no buying or grading advice.
Why a refractometer struggles: alexandrite against colour-change corundum
Birefringence does not separate them. GIA gives alexandrite 0.008 to 0.010, and ruby and sapphire 0.008 to 0.010: identical ranges. The chrysoberyl sheet works out at 0.010 (γ minus α); the IGS locality table gives 0.009 to 0.010.
The index gap depends on whose figures you use. On GIA’s pages, alexandrite’s highest index, 1.755, is 0.007 below corundum’s lowest, 1.762. On the Handbook sheets, chrysoberyl’s 1.756 is 0.003 below corundum’s ε of 1.759. The IGS table gives Ural alexandrite a γ of 1.759 and Zimbabwean 1.758, which meet or nearly meet the corundum sheet’s lowest value. A single reading near 1.759 therefore decides nothing on its own.
What does help, and its own caveat. Chrysoberyl is biaxial, with three principal indices and three pleochroic colours: X red, Y yellow-orange, Z emerald-green on the sheet; green, orange and purple-red per GIA. Corundum is uniaxial, with two indices and two pleochroic colours on its sheet, O and E. But the Handbook of Mineralogy corundum sheet also records corundum as commonly anomalously biaxial, so even optic character needs an experienced hand. This is the documented limit of home and counter testing; the general checks are on how to tell if a crystal is fake, and corundum’s own data are on corundum.
When each name is the wrong word
“Alexandrite” is wrong for colour-change sapphire, for synthetic corundum with an alexandrite-like change, for chrysoberyl that does not change colour, and, by the IGS’s account, sometimes for chrysoberyl whose change is not the classic green to red. “Chrysoberyl” is right but incomplete for an alexandrite: true at species level, silent about the colour change. “Synthetic alexandrite” is the correct name for laboratory-grown material, which the IGS treats as alexandrite that is not natural.
History, per GIA and the IGS. Alexandrite was discovered in Russia’s Ural Mountains in the 1830s; the IGS says it was named in 1834 for the future Czar Alexander II. GIA now lists Sri Lanka, East Africa and Brazil as sources; the IGS adds Madagascar, Myanmar and Zimbabwe. The Handbook’s chrysoberyl localities, including Brazil’s Minas Gerais and the Izumrudnye mines near Yekaterinburg, are on the species page.
For a collection label, the species goes first and the variety after it: chrysoberyl, variety alexandrite, with the locality. The convention is on how to label and catalogue a mineral collection. Nothing on this site is offered for sale; the wanted list is the only commercial route.