On this page
UnderstandWhat it is, what people ask, how far this page goes
Natural inorganic gem materials · Mineral / gemstone variety · Natural identity; treatment status unknown
Alexandrite
The colour-change variety of Chrysoberyl; GB/T 16552-2017 Table A.1 lists the basic name "alexandrite". This page compares how the major standards and institutions name it, what must be disclosed when selling it, whether it can be worn every day, how it is treated and identified, and which source each conclusion comes from.
Price, rarity and origin are outside the scope of this wiki.
Questions people ask about Alexandrite
Every sentence below is followed by the registered fact it rests on; answers add no new facts and promise no outcome.
Q1Why does alexandrite change colour?
Alexandrite looks green in daylight or fluorescent light and brownish or purplish red under incandescent or candle light, because of the way the mineral absorbs light.GIA Alexandrite DescriptionIt is also strongly pleochroic, showing green, orange and purple-red in different directions, but the colour change itself comes from that unusual light absorption, not from pleochroism.GIA Alexandrite Description
Q2How can you tell natural alexandrite from synthetic or imitation stones?
Alexandrite's appearance does not reveal whether it is natural, synthetic or an imitation; separating them takes laboratory testing of composition and spectral features.CIBJO Gemstone Book 2022On laboratory reports, alexandrite means chromium-bearing chrysoberyl that changes colour, compared under daylight and incandescent light at about 30 cm.LMHC Information Sheet #9Whether one particular bead is natural, treated or synthetic — only a laboratory report can settle that.What this page can answer
Q3What is alexandrite made of?
Alexandrite is a rare colour-change variety of the mineral chrysoberyl.GIA Alexandrite DescriptionIts formula is BeAl2O4, and it may contain elements such as iron, chromium and vanadium.GB/T 16553—2017To count as alexandrite, the main hue in daylight must differ from the hue under incandescent light.CIBJO Gemmological Laboratories Book 2024
Q4Is alexandrite durable enough for an everyday ring?
At Mohs 8.5, with excellent toughness and no cleavage, it is a sound choice for rings and other everyday pieces that are easily knocked.GIA Gem Encyclopedia (care guide)Under normal wear heat, light and everyday chemicals are unlikely to harm it.GIA Gem Encyclopedia (care guide)
Q5How should alexandrite be cleaned?
Warm soapy water is always safe, and ultrasonic and steam cleaners are usually fine too.GIA Gem Encyclopedia (care guide)Stones with filled fractures should be cleaned only with warm soapy water.GIA Gem Encyclopedia (care guide)
Q6Where does alexandrite form?
As a chrysoberyl, alexandrite occurs in beryllium-bearing systems such as granitic pegmatites.G&G Summer 2025The chrysoberyl crystallizes where chromium is present.GIA Alexandrite Description
Q7What makes good-quality alexandrite?
Fine alexandrite is green to bluish green in daylight and red to purplish red in incandescent light, with moderately strong to strong saturation, and clean material with a good colour change and strong colours is rated much higher.GIA Alexandrite Quality Factors
What this page can answer
This page covers
- How Alexandrite forms and what gives its colourFormation setting, process and timescale; where its colour and optical effects come from, each finding graded and sourced
- How to identify AlexandriteIdentification points from the research literature; how far lab testing can go
- Treatments and enhancements of AlexandriteThe enhancements and treatments the GB/T and JJA/AGL tables list
- Caring for and wearing AlexandriteCleaning, heat, chemicals and light, as the cited sources give them
- Hardness, density and refractive index of AlexandriteEach value with its source and check date
- Alexandrite in English, Chinese and Japanese; national standard namesNames in four languages, the GB/T standard name and the suggested listing name; and: Which of GIA, FTC, CIBJO and Gem-A have a name for it on record, and do those agree?
- Listing and disclosing AlexandriteThe listing name to use; what must be disclosed before sale; how lab reports word it
- Standard clauses that define AlexandriteWhich clause defines it, each cross-checked
What we cannot conclude
- Whether one particular bead is natural, treated or synthetic — only a laboratory report can settle that.
- Geographic origin, unless an origin report accompanies the item.
- Price, rarity or investment value: this wiki covers naming and disclosure only.
Material research: formation, causes and history
What authoritative sources say about how this material forms, what causes its colour and optical effects, where its name comes from and how people have used it. Each statement carries an evidence grade and its sources; it describes the material in general, not any specific piece.
How it forms
Alexandrite is the rare colour-change gem variety of chrysoberyl (BeAl2O4). It is green in daylight or fluorescent light and changes to brownish or purplish red under incandescent or candle light; this striking light-source-dependent change is often called 'the alexandrite effect'. The change results from the mineral's complex (selective) absorption of light, not from pleochroism — although alexandrite shows three pleochroic colours (green, orange, purple-red), the colour change is independent of pleochroism. As a chrysoberyl, alexandrite occurs in Be-bearing systems such as granitic pegmatites and is expensive owing to its scarcity, especially in large sizes.
Scope: Covers the colour-change mechanism and identity boundaries of chrysoberyl alexandrite; synthetic alexandrite and origin determination are outside the scope of this record.
Sources GIA Alexandrite Description · G&G Summer 2025
Where it forms
Be-bearing systems such as granitic pegmatites, where chrysoberyl displays light-source-dependent colour change.
Sources G&G Summer 2025
How it forms, step by step
Chrysoberyl crystallises in a Cr-bearing system.
Sources GIA Alexandrite Description
The crystal selectively absorbs visible light, so transmitted colour changes with the light source's spectral distribution.
Sources GIA Alexandrite Description
Thus the same crystal looks green in daylight and red under incandescent light, giving the colour-change effect.
Sources GIA Alexandrite Description
Link to appearance
Alexandrite is green in daylight/fluorescent light and brownish or purplish red under incandescent/candle light; the change is independent of pleochroism.
Sources GIA Alexandrite Description
Timescale
The colour change is a solid-state absorption property and does not entail a new formation timescale.
Sources GIA Alexandrite Description
Related base materials
- Chrysoberyl: Mineral parent: this variety belongs to the mineral species chrysoberyl (BeAl2O4)
Supporting findings
As a chrysoberyl, alexandrite occurs in Be-bearing systems such as granitic pegmatites.
Evidence grade AScope: Describes the pegmatite setting without excluding others.
Recorded localities
Authoritative sources list the localities below; the list is not exhaustive.
Africa
- East AfricaAmong the sources of most alexandrite today
Sources GIA Gem Encyclopedia
- Tunduru, Tanzania
Sources Gems & Gemology Winter 2000
- Ilakaka, Madagascar
Sources Gems & Gemology Winter 2000
Asia
- Sri LankaAmong the sources of most alexandrite today
Sources GIA Gem Encyclopedia · Gems & Gemology Winter 2000
- IndiaOdisha and Andhra Pradesh
Sources Gems & Gemology Winter 2000
Europe
- Ural Mountains, RussiaClassic deposits first found in 1830; no longer productive
Sources GIA Gem Encyclopedia · Gems & Gemology Winter 2000
South America
- BrazilAmong the sources of most alexandrite today
Sources GIA Gem Encyclopedia · Gems & Gemology Winter 2000
These are localities recorded by authoritative sources, not an origin finding for any individual piece. The CIBJO Gemstone Book (2022, §4.2.3) says a place of origin names where a gem was mined or harvested, is a matter of opinion, does not imply a level of quality, and that cutting, processing or exporting centres must not be used to imply origin. See how far testing can go on this page, the origin determination guide and the overview of recorded localities.
Causes of colour and optical effects
Alexandrite changes colour with the light source — green in daylight/fluorescent light, brownish or purplish red under incandescent/candle light — owing to the mineral's complex light absorption.
Evidence grade AScope: Describes the colour-change phenomenon and its absorption mechanism.
Sources GIA Alexandrite Description
Alexandrite's striking colour change is often called 'the alexandrite effect'.
Evidence grade AScope: The conventional name for the phenomenon.
Sources GIA Alexandrite Description
Alexandrite is strongly pleochroic (green, orange, purple-red), but its colour change arises from unusual light absorption rather than pleochroism.
Evidence grade AScope: Makes clear that colour change and pleochroism are distinct.
Sources GIA Alexandrite Description
How it is identified
Alexandrite's colour shifts with the light source, and its appearance does not reveal whether it is natural, synthetic or an imitation. Separating them calls for laboratory testing of composition and spectral features, read together with internal features; the conclusion must come from an accredited laboratory and is not for the reader to make unaided.
Evidence grade AScope: Alexandrite natural/synthetic/imitation determination is laboratory testing, to be issued by an accredited body.
Sources CIBJO Gemstone Book 2022
Other research findings
Alexandrite is a rare colour-change variety of the mineral chrysoberyl.
Evidence grade AScope: Defines only the variety-to-species relation.
Sources GIA Alexandrite Description
Fine alexandrite is green to bluish green in daylight and red to purplish red in incandescent light, with moderately strong to strong saturation; clean material with a good colour change and strong colours is rated much higher.
Evidence grade BScope: Quality factors as described by one educational source; not a grading standard and not a statement about the value of any piece.
Sources GIA Alexandrite Quality Factors
Limits of this research
- Research status: Formation, occurrence or other material-specific findings found in authoritative sources
- The chromophore (Cr3+) and absorption-band details of alexandrite are not directly given in the available sources.
- Synthetic alexandrite and origin determination are outside the formation scope.
Methodology
- Origin determination and its limits
- Quality grading and value factors
- How gemmology became a technical discipline
Evidence grades
- A
- Standards bodies, government geological surveys, peer-reviewed research and museum records
- B
- Institutional educational material
- C
- Specialist databases or cautious readings
A statement is never graded above its strongest source.
This section is LumaLark's own factual restatement of public authoritative sources, credited item by item; it contains no verbatim excerpts, images or third-party logos.
DecideListing name, disclosure, care and treatments
- Suggested listing name
- Alexandrite
GB/T 16552—2017 Table A.1 “Alexandrite” · IMA Mineral List 2026-07 “Chrysoberyl”
Construction or treatment status
Natural identity; treatment status unknown
Related:Disclosure and cautions
This page cannot answer
Natural? · Origin · Price
A lab report settles these; this wiki covers naming and disclosure.
Related:What this page can answer
Answer at a glance
Alexandrite is Colour-change chrysoberyl variety; use "Alexandrite" for listings, and disclose any known treatments.
Evidence
- GB/T · Table A.1, row 变石 (Alexandrite)
What this means for you
Before buying, check the recommended listing name "Alexandrite" and any disclosed treatments on this page, and ask the seller for a grading report if in doubt.
Known uncertainty
- Last reviewed
- 2026-09-01
Care and wear
Normal care for every gemstone (CIBJO Gemstone Book §6.1), in brief:
- Handle it gently.
- Store pieces apart when not worn, so they cannot scratch each other.
- Clean with warm soapy water and a soft brush.
- Use ultrasonic cleaners only with caution.
The §6.1 wording and the full list of §6.2 special-care letters cited on this page are on the general gem care page.
Care
care (cleaning)2 sources compared
Alexandrite — care (cleaning): Warm soapy water is always safe; ultrasonic and steam cleaners are usually fine too.
GIA Gem Encyclopedia (care guide)
- Treatment state
- any treatment state
Source & check 2026-09-26
- Source
- GIA Gem Encyclopedia — Alexandrite Care and Cleaning Guide: Section “Cleaning” (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Alexandrite — care (cleaning): Some stones are susceptible to damage from ultrasonic cleaning. Do not expose them to ultrasonic cleaning.
CIBJO Gemstone Book 2022
CIBJO Gemstone Book §6.2:special-care code j
- Treatment state
- treated
- Only after these treatments
- fissure filling with resin
Source & check 2026-09-25
- Source
- CIBJO Blue Book — Official Gemstone Book (Coloured Stone Commission 2022) (CIBJO): §8 Annex C, Alexandrite, p.39; §6.2 j (locator checked 2026-09-25)
- Fact checked on
- 2026-09-25
Alexandrite — care (cleaning): Stones with filled fractures should be cleaned only with warm soapy water
GIA Gem Encyclopedia (care guide)
- Treatment state
- treated
- Only after these treatments
- filling
Source & check 2026-09-26
- Source
- GIA Gem Encyclopedia — Alexandrite Care and Cleaning Guide: Section “Treatment and durability considerations” (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
care (chemicals)2 sources compared
Alexandrite — care (chemicals): Under normal wear it is stable: heat, light and everyday chemicals are unlikely to harm it.
GIA Gem Encyclopedia (care guide)
- Treatment state
- any treatment state
Source & check 2026-09-26
- Source
- GIA Gem Encyclopedia — Alexandrite Care and Cleaning Guide: Section “Stability” (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Alexandrite — care (chemicals): Treatments with dye, oil, resin, wax or plastic are not permanent; keep it away from all solvents (including dish-washing liquids), chemicals and heat.
CIBJO Gemstone Book 2022
CIBJO Gemstone Book §6.2:special-care code k
- Treatment state
- treated
- Only after these treatments
- fissure filling with resin
Source & check 2026-09-25
- Source
- CIBJO Blue Book — Official Gemstone Book (Coloured Stone Commission 2022) (CIBJO): §8 Annex C, Alexandrite, p.39; §6.2 k (locator checked 2026-09-25)
- Fact checked on
- 2026-09-25
care (wear)2 sources compared
Alexandrite — care (wear): At Mohs 8.5, with excellent toughness and no cleavage, it is a sound choice for rings and other pieces that are worn every day and easily knocked.
GIA Gem Encyclopedia (care guide)
- Treatment state
- any treatment state
Source & check 2026-09-26
- Source
- GIA Gem Encyclopedia — Alexandrite Care and Cleaning Guide: Section “Hardness and toughness” (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Alexandrite — care (wear): cleaves or fractures easily or is brittle (e.g. rubbed facet edges); wear with care.
CIBJO Gemstone Book 2022
CIBJO Gemstone Book §6.2:special-care code b
- Treatment state
- treated
- Only after these treatments
- fissure filling with resin
Source & check 2026-09-25
- Source
- CIBJO Blue Book — Official Gemstone Book (Coloured Stone Commission 2022) (CIBJO): §8 Annex C, Alexandrite, p.39; §6.2 b (locator checked 2026-09-25)
- Fact checked on
- 2026-09-25
Alexandrite — care (special care): normal care
AGTA Gemstone Information Manual, 17th ed.
- Treatment state
- untreated
Source & check 2026-09-26
- Source
- AGTA Gemstone Information Manual, 17th edition (August 2026) (AGTA): p.VII, Gemstone Information Chart, Alexandrite N, CARE REQUIRED / SPECIAL ADVICE (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Each row's “Source & check” expands to the full source; the date beside it is the fact check date.
Common care questions and matching entries
CleaningThe Gemological Institute of America (GIA) states that Alexandrite can always be cleaned safely with warm soapy water, and that ultrasonic and steam cleaners are usually fine too. The CIBJO Blue Book states that stones with fractures filled with resin must not be cleaned ultrasonically; GIA also states that filled stones should be cleaned only with warm soapy water. ChemicalsOn chemicals, GIA states that under normal wear it is stable, and that heat, light and everyday chemicals are unlikely to harm alexandrite; the CIBJO Blue Book states that stones with resin-filled fractures should be kept away from all solvents (including dish-washing liquids), chemicals and heat, and that treatments with dye, oil, resin, wax or plastic are not permanent. WearOn wear, GIA states that at Mohs 8.5, with excellent toughness and no cleavage, it is a sound choice for rings and other pieces that are worn every day and easily knocked; the CIBJO Blue Book states that stones with resin-filled fractures cleave or fracture easily, so wear them with care. General careThe American Gem Trade Association (AGTA) Gemstone Information Manual states that untreated stones need only general care.
This table scrolls sideways on narrow screens.
| Question | Matching entries |
|---|---|
| Can it go in an ultrasonic or steam cleaner? | Warm soapy water is always safe; ultrasonic and steam cleaners are usually fine too; care (cleaning); Stones with filled fractures should be cleaned only with warm soapy water |
| Contact with acids, alkalis and household chemicals | Under normal wear it is stable: heat, light and everyday chemicals are unlikely to harm it; Treatments with dye, oil, resin, wax or plastic are not permanent; keep it away from all solvents (including dish-washing liquids), chemicals and heat |
| Wearing limits (knocks, settings) | At Mohs 8.5, with excellent toughness and no cleavage, it is a sound choice for rings and other pieces that are worn every day and easily knocked; cleaves or fractures easily or is brittle (e.g. rubbed facet edges); wear with care |
Care entries by treatment state
The same entries grouped by the treatment state each applies to; each links to its full wording and source. Letters are CIBJO special-care codes, explained on the gemstone care page.
any treatment state
- Warm soapy water is always safe; ultrasonic and steam cleaners are usually fine too
- Under normal wear it is stable: heat, light and everyday chemicals are unlikely to harm it
- At Mohs 8.5, with excellent toughness and no cleavage, it is a sound choice for rings and other pieces that are worn every day and easily knocked
untreated
treated (Only after these treatments: fissure filling with resin)
- care (cleaning) §6.2 j
- Treatments with dye, oil, resin, wax or plastic are not permanent; keep it away from all solvents (including dish-washing liquids), chemicals and heat §6.2 k
- cleaves or fractures easily or is brittle (e.g. rubbed facet edges); wear with care §6.2 b
treated (Only after these treatments: filling)
How lab reports word it
Alexandrite — how lab reports word it (definition used on reports): On reports, alexandrite is chromium-bearing chrysoberyl that changes colour, compared under daylight and incandescent light (or LED equivalents), each at a distance of about 30 cm.
LMHC Information Sheet #9
Definition in the information sheet (original wording): a chromium bearing variety of chrysoberyl showing a colour-change
- Case
- when the variety name may be used
Source & check 2026-09-26
- Source
- LMHC Information Sheet #9, Version 4, February 2023 (LMHC): p.1, “Definitions” (Information Sheet #9) (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Alexandrite — how lab reports word it (identification line): The description gives two colours, one in daylight and one under incandescent light; all treatments must be stated.
LMHC Information Sheet #9
Wording on the report: in daylight
- Case
- when the variety name may be used
Source & check 2026-09-26
- Source
- LMHC Information Sheet #9, Version 4, February 2023 (LMHC): p.1, “Report wording”, B (Information Sheet #9) (locator checked 2026-09-28)
- Fact checked on
- 2026-09-26
VerifyNames, standards, technical facts, clauses and sources
Names
The name register below lists one name for Alexandrite in a non-Latin script: 1 with no restriction recorded on use as a name.
Standard and listing namesThe Chinese standard name for Alexandrite is alexandrite (GB/T 16552—2017 Table A.1), and the suggested listing name is also Alexandrite; it is also known as colour-change chrysoberyl. Names in four languagesNames are registered in four languages: Simplified Chinese, Traditional Chinese, English (Alexandrite) and Japanese. The GSJ (Japan) formal name is Alexandrite, written as a colour-change variety of chrysoberyl, and the mineralogical name is Colour-change chrysoberyl variety. Institution usageOn authority wording, this site records only the CIBJO wording: the CIBJO Gemmological Laboratories Book 2024 records Alexandrite; the FTC text on file has no wording for Alexandrite (checked); GIA and Gem-A are unchecked.
Name register
Every name recorded for this entry, with how it is classified, whether it may be matched to this entry automatically, whether it may be used as a product name, and the clause it rests on.
This table scrolls sideways on narrow screens.
| Name | Type | Matching | Use as a name | Basis |
|---|---|---|---|---|
| no restriction recorded (1) | ||||
| 变色金绿宝石Simplified Chinese | synonym | matched automatically | no restriction recorded | GB/T 16552—2017 5.3.3 |
How each authority words this name: see Names › Authority wording.
- GSJ (Japan) formal name
- アレキサンドライト／金緑石変種
- Chinese formal name
- 变石 (GB/T 16552—2017 Table A.1)
- Mineralogical name
- Colour-change chrysoberyl variety
Four-language names
- 简体中文
- 变石
- 繁體中文
- 變石
- English
- Alexandrite
- 日本語
- アレキサンドライト
See also: Misleading and prohibited trade names · Supplementary name index
Classification
- Origin
- Natural materials
- Material domain
- Natural inorganic gem materials
- Browsing family
- Oxide minerals
- Identity tier
- Mineral / gemstone variety
- Mineral chemical class
- Oxides / hydroxides
- Construction or treatment status
- Natural identity; treatment status unknown
Treatments listed by standards
Alexandrite is registered in the table of principal gem names of the JJA/AGL (Japan) definitions and nomenclature of gemstones and ornamental materials, November 2025 revision, as follows: gem name Alexandrite, species Chrysoberyl, colour green to bluish green, with the note distinct colour change to red to purplish red; the JJA/AGL listing also includes an untreated tier. How to read the JJA/AGL table is explained on the Gem treatments page.
JJA/AGL (Japan) table of principal gem names, 2025
This table scrolls sideways on narrow screens.
| Gem name | Species | Colour | Listed in the table | Notes |
|---|---|---|---|---|
| Alexandrite | Chrysoberyl | green to bluish green | an untreated tier is listed | distinct colour change to red to purplish red |
JJA/AGL definitions and nomenclature (2025 revision), table of principal gem names, p.11
How to read the JJA/AGL table: see the Gem treatments page.
What it is and how it's identified
The composition of Alexandrite is BeAl2O4 and may contain elements such as Fe, Cr and V; its phase is chrysoberyl. The structure is crystalline, orthorhombic, with a tabular or short prismatic crystal habit; Mohs hardness 8–8.5, with three directions of imperfect cleavage; density 3.71–3.75 g/cm³, derived from the cited clause value of 3.73 and the permitted tolerance of ±0.02; optical character anisotropic, biaxial, positive; refractive index 1.74–1.759, derived from the cited clause value of 1.746–1.755 and the permitted tolerances of +0.004 and −0.006; birefringence 0.008–0.01. Registered optical effects are chatoyancy (visible) and colour change (visible). Untreated, pleochroism is trichroic and strong, green, orange-yellow and purplish red; untreated fluorescence is none to moderate, purplish red; untreated lustre is vitreous to subadamantine.
Registered material facts
Each row carries its own source and check date and can be cited on its own; “—” means the cited source gives no value, not “none”.
Definition
Alexandrite — composition (chemistry): BeAl2O4, elements such as Fe,Cr and V may be contained.
GB/T 16553—2017
- Does this standard apply
- applies to this entry
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.6 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Alexandrite — composition (phase): chrysoberyl
CIBJO Gemmological Laboratories Book 2024
Source & check 2026-09-22
- Source
- Fact checked on
- 2026-09-22
Structure
Alexandrite — structure (overall): crystalline
GB/T 16553—2017
- Does this standard apply
- applies to this entry
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.6 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Alexandrite — structure (crystal system): orthorhombic
GB/T 16553—2017
- Does this standard apply
- applies to this entry
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.6 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Alexandrite — structure (crystal habit): stubby prisms or tablets
GB/T 16553—2017
- Does this standard apply
- applies to this entry
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.6 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Durability
Alexandrite — Mohs hardness: 8–8.5
GB/T 16553—2017
Reference points on this site: Talc 1–3, Fluorite 4, Apatite 5–5.5, Orthoclase 6–6.5, Topaz 8, Diamond 10 (Source: GB/T 16553—2017); Gypsum 1.5–2, Calcite 3, Quartz 7 (Source: Handbook of Mineralogy); Corundum 9 (Source: GIA Gem Encyclopedia (care guide))
- Does this standard apply
- applies to this entry
- General note
- hardness only, not durability
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.6 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Alexandrite — cleavage: imperfect in three directions
GB/T 16553—2017
- Does this standard apply
- applies to this entry
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.6 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Physical properties
Alexandrite — density: 3.71–3.75 g/cm³
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- Qualification
The clause we cite gives 3.73, with a stated tolerance of ±0.02. The range shown here is worked out from that.
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.6 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Optical
Alexandrite — optic character: biaxial, optically positive (anisotropic)
GB/T 16553—2017
- Does this standard apply
- applies to this entry
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.6 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Alexandrite — refractive index: 1.74–1.759
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- Qualification
The clause we cite gives 1.746–1.755, with a stated tolerance of +0.004 / -0.006. The range shown here is worked out from that.
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.6 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Alexandrite — birefringence: 0.008–0.01
GB/T 16553—2017
- Does this standard apply
- applies to this entry
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.6 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Alexandrite — pleochroism: strong trichroism: green, orange-yellow, purple-red.
GB/T 16553—2017
- Treatment state
- untreated
- Does this standard apply
- applies to this entry
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.6 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Alexandrite — fluorescence (overall): none to moderate, violet-red
GB/T 16553—2017
UV fluorescenceviolet-rednone–moderateDots are illustrative colours built from the colour names, not measured values
- Treatment state
- untreated
- Does this standard apply
- applies to this entry
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.6 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Alexandrite — spectrum (UV-visible): 680 nm strong absorption peak; 678 nm strong absorption peak; 665 nm weak absorption peak; 655 nm weak absorption peak; 645 nm weak absorption peak; 580~630 nm partial absorption band; 476 nm weak absorption peak; 473 nm weak absorption peak; 468 nm weak absorption peak; absorption in the violet region.
GB/T 16553—2017
- Does this standard apply
- applies to this entry
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.6 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Alexandrite — spectrum (infrared): Chrysoberyl's Be-O and Al-O lattice vibrations produce its diagnostic bands in the mid-IR.
GB/T 16553—2017
- Does this standard apply
- applies to this entry
Source & check 2026-09-22
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.6 (locator checked 2026-09-22)
- Fact checked on
- 2026-09-22
Alexandrite — optical effect (chatoyancy): seen
GB/T 16553—2017
- Does this standard apply
- applies to this entry
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.6 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Alexandrite — optical effect (colour change): seen
GB/T 16553—2017
- Does this standard apply
- applies to this entry
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.6 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Alexandrite — magnification: gas-liquid inclusions, fingerprint-like inclusions, "silk" inclusions, twin striations.
GB/T 16553—2017
- Treatment state
- untreated
- Does this standard apply
- applies to this entry
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.6 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
body colour2 sources compared
Alexandrite — body colour: essentially bluish green to green in daylight and purple to red, to purplish brown in incandescent light.
CIBJO Gemmological Laboratories Book 2024
- Treatment state
- untreated
- Qualification
Chapter 7 of the CIBJO Gemmological Laboratories Book describes it as changing colour with the light source (daylight versus incandescent light), as it does for Colour-Change Garnet and Colour-change Sapphire.
- General note
- colour alone is not identity
Source & check 2026-09-26
- Source
- Fact checked on
- 2026-09-26
Alexandrite — body colour: colour change — in daylight yellow-green, brownish green or grey-green through to blue-green; under incandescent light orange-red or brownish red through to purplish red.
GB/T 16553—2017
- Treatment state
- untreated
- Does this standard apply
- applies to this entry
- Qualification
The colours GB/T 16553—2017 lists for Synthetic Alexandrite overlap with this entry: blue-green in daylight and brownish red to purplish red in incandescent light.
- General note
- colour alone is not identity
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.6 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
How the sources relate
- CIBJO Gemmological Laboratories Book 2024 and GB/T 16553—2017
Both describe a bluish green in daylight and a red-to-purple range in incandescent light. GB/T 16553—2017 also lists yellow-green, brownish green and grey-green in daylight and orange-red and brownish red in incandescent light; the CIBJO Gemmological Laboratories Book also lists purplish brown in incandescent light.
- CIBJO definitions
- chatoyancy, colour change
Quality factors
Alexandrite — quality factor (lustre): vitreous to subadamantine
GB/T 16553—2017
- Treatment state
- untreated
- Does this standard apply
- applies to this entry
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.6 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Each row's “Source & check” expands to the full source; the date beside it is the fact check date.
This material (RI / SG midpoints): 1.749 / 3.73; Closest values: 1Cobalt Spinel 1.723 / 3.63, 2Grossular 1.745 / 3.9, 3Malachite 1.782 / 3.67, 4Rhodolite 1.755 / 3.9, 5Benitoite 1.78 / 3.65
Show the full chart (330 registered materials)
Outside the full chart's range, drawn as triangles at the edge (RI / SG midpoints): Hematite 3.045/5.12, Synthetic Rutile 2.76/4.26, Rutile 2.753/4.23, Synthetic Moissanite 2.67/3.22
Testing and market
To tell Alexandrite from other varieties in the untreated state, check whether the same stone shows a different dominant hue in daylight and under incandescent light; for the comparison, daylight conditions are taken as 5500–6500 K and incandescent conditions as 2700–3600 K. Under the CIBJO laboratory protocol, the items needing particular checks include clarity enhancement, synthetics and a distinct colour change; the protocol's note on test methods names the special optical effects as chatoyancy and colour change, and colour is judged on the basis of a distinct colour change.
The tests the CIBJO laboratory protocol requires for this material, and what each method means, are in the protocol table on the laboratory testing page: §6.1.2.
How far testing can go
Alexandrite — criteria for distinction from other varieties: • Colour-change: main hue in daylight differs from that seen in incandescent light. • Daylight: for the purposes of this comparison calibrated daylight corresponding to a range between 5500K to 6500K shall be used. • Incandescent light: for the purposes of this comparison standard incandescent light corresponding to a range between 2700K and 3600K shall be used.
CIBJO Gemmological Laboratories Book 2024
- Treatment state
- untreated
Source & check 2026-09-22
- Source
- Fact checked on
- 2026-09-22
Alexandrite — what the CIBJO laboratory protocol says to watch for: clarity enhancement, synthetics, clear colour-change
CIBJO Gemmological Laboratories Book 2024
- Treatment state
- any treatment state
Source & check 2026-09-26
- Source
- Fact checked on
- 2026-09-26
Alexandrite — notes on test methods in the CIBJO laboratory protocol:
| Test method | What the protocol notes for it |
|---|---|
| Phenomena: | Cat’s-eye, colour-change; |
| Colour call: | Clear colour-change |
CIBJO Gemmological Laboratories Book 2024
- Treatment state
- any treatment state
Source & check 2026-09-26
- Source
- Fact checked on
- 2026-09-26
Each row's “Source & check” expands to the full source; the date beside it is the fact check date.
Clause-level definitions
Alexandrite is defined directly in the CIBJO Gemmological Laboratories Book 2024 under the term Alexandrite; the CIBJO wording is quoted in full under Clause-level definitions on this page. Cross-check result: defined directly by CIBJO, also appearing in the GB/T annex.
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| Term | Clause | Definition | Cross-check |
|---|---|---|---|
| Alexandrite | 7.2.1.6 | Colour-changing chromium bearing variety of chrysoberyl, showing a colour change: essentially bluish green to green in daylight and purple to red, to purplish brown in incandescent light • Colour-change: main hue in daylight differs from that seen in incandescent light. • Daylight: for the purposes of this comparison calibrated daylight corresponding to a range between 5500K to 6500K shall be used. • Incandescent light: for the purposes of this comparison standard incandescent light corresponding to a range between 2700K and 3600K shall be used | Defined directly by CIBJO; also present in the GB/T annex. |
Evidence and sources
Authority basis and clause sources
Sources
- CIBJO – The World Jewellery Confederation. Gemmological Laboratories Book (Blue Book), Gemmological Commission 2024-1.
- CIBJO – The World Jewellery Confederation. The Gemstone Book (Blue Book), 2022.
- SAMR / SAC (China). GB/T 16552—2017 Gems — Nomenclature.
- RRUFF Project, in partnership with the IMA – International Mineralogical Association. IMA Mineral List.
- Geological Survey of Japan, AIST (Japan). Museum mineral specimens, browse by classification.
Further reading
Recorded cultural contexts
The U.S. Jewelers of America roster lists Alexandrite for June; and Japan's JJA 2021 revised roster lists Alexandrite for June. This records trade-association convention only; it does not establish material identity, natural origin, treatment, provenance, or effect.
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| Publisher or holder | Region | From / period | Source and locator |
|---|---|---|---|
| Jewelers of America | United States | from 1952 | Jewelers of America, “Birthstone Jewelry” (web page, consulted 2026-08-22) Birthstone roster table, June row: Alexandrite |
| Japan Jewellery Association | Japan | from 20 December 2021 | Tanjoseki (Japanese birthstone roster, Japan Jewellery Association page; revision of 20 December 2021) 2021 revised birthstone roster, June row: Alexandrite |
Related entries and topic cluster
Parent entry and related pages on this site. Rows marked “Planned” are suggested new content and have no link yet.
This table scrolls sideways on narrow screens.
| Page | Content | Status |
|---|---|---|
| Browsing family | Oxide minerals | Live |
| Related articles | To be added (placeholder) | Planned |
Who maintains this page
The material facts in the Alexandrite entry are maintained by the LumaLark wiki and matched one by one to the standard clauses or institutional sources they cite: every fact carries its source (with a clause or page locator) and a check date, so it can be traced back to the original; clause-level definitions also carry a cross-check result. The entry exists so that buyers and sellers can check naming, disclosure and material facts item by item.