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
Colour-change Sapphire
Also known asalexandrite sapphire (not to be used as a name)
A gem corundum variety that changes colour under different light sources; it must not be written as "Alexandrite Sapphire". 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.
What this page can answer
This page covers
- How Colour-change Sapphire 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 Colour-change SapphireIdentification points from the research literature; how far lab testing can go
- Treatments and enhancements of Colour-change SapphireThe enhancements and treatments the GB/T and JJA/AGL tables list
- Caring for and wearing Colour-change SapphireCleaning, heat, chemicals and light, as the cited sources give them; durability indicators and wearing advice
- Hardness, density and refractive index of Colour-change SapphireEach value with its source and check date
- Colour-change Sapphire 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 Colour-change SapphireThe listing name to use; what must be disclosed before sale
- Standard clauses that define Colour-change SapphireWhich 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
Color-change sapphire is sapphire (corundum) whose apparent hue differs with the light source. The color itself does not change; rather the crystal absorbs different wavelengths differently: under daylight (D65), which is richer in blue-green, it transmits more green light and appears greener/bluer, while under incandescent light (A), richer in orange-red, it transmits proportionally more of those wavelengths and appears purplish. The color and color change relate to trace chromophores (color centers), notably vanadium (V3+); in natural corundum, trace chromophores were incorporated during growth or later equilibration in nature. Color change is usually defined as a hue change of more than one adjacent hue position (e.g. blue to red, or green to red).
Scope: Applies to explaining the optical mechanism of colour change in colour-change sapphire (differences in absorption under different light sources) and its colouring sources; does not address other optical effects such as asterism, nor specific commercial locality names.
Sources G&G Spring 2020
Where it forms
Vanadium-bearing (and Cr-bearing) host rocks/melts: high-vanadium sapphires are reported from localities such as the Mogok Stone Tract in Myanmar.
Sources G&G Spring 2020
Corundum growth or later equilibration: trace chromophores enter the lattice during crystal growth or afterward.
Sources G&G Spring 2020
How it forms, step by step
Corundum crystallizes from a melt or fluid containing trace chromophores (e.g. vanadium, chromium), and V enters the lattice as V3+.
V3+ produces an absorption band near 580 nm in the visible region, with wavelength-dependent absorption strength.
Under blue-green-rich daylight the crystal transmits more green (appearing greener/bluer), while under orange-red-rich incandescent light it transmits more red (appearing purplish), so the eye sees a color change.
Cut orientation affects the observed color and the strength of the color change: the color can differ markedly depending on direction through the crystal.
Link to appearance
The color-change effect arises from the crystal’s wavelength-dependent absorption: more green is transmitted under daylight (greener/bluer) and more red under incandescent light (more purple); cut orientation also affects the color seen.
Sources G&G Spring 2020
Timescale
The available authoritative sources give no growth duration, absolute age, or specific timescale for the formation of color change in sapphire.
Sources G&G Spring 2020
Supporting findings
The colors of natural corundum are caused by trace impurities (chromophores) or other point defects incorporated into the lattice during growth or later equilibration in nature.
Evidence grade AScope: The general mechanism for natural corundum color; not specific to any one color-change variety.
High-vanadium corundum from Myanmar’s Mogok Stone Tract (vanadium up to about 2000 ppma) has been reported with colors from “slate” to purple, in some cases with color change.
Evidence grade BScope: A reported case of high-vanadium samples from a specific locality; not representative of all color-change sapphire sources.
Causes of colour and optical effects
In colour-change sapphire, both the colour and the change of colour are tied to chromophores such as vanadium (V3+). A synthetic stone of this kind produced by the Czochralski method displays the colour that V3+ gives on its own.
Evidence grade AScope: Uses a V3+-colored synthetic color-change sapphire as the example; natural color-change sapphire may differ in vanadium content and chromophore combinations.
The color change comes from absorption differences under different light sources: daylight (D65) is richer in blue-green so the crystal appears greener, while incandescent light (A) is richer in orange-red so it appears more purplish.
Evidence grade AScope: The mechanism is illustrated with the V3+ chromophore and the D65/A light sources, an authoritative statement combining qualitative and quantitative results.
How it is identified
That a sapphire changes colour under different lighting is not by itself proof of natural origin or of where it formed. Laboratories combine several lines of evidence: magnification of inclusions and growth features; routine tests such as refractive index, specific gravity and polariscope behaviour; ultraviolet fluorescence; and spectroscopy (for example FTIR, UV-Vis-NIR and Raman). Trace-element chemistry measured by EDXRF or LA-ICP-MS helps separate natural from synthetic corundum and, compared with a reference collection, may point to a geographic origin; glass-filled fractures and coatings are caught by clues such as anomalous luster, gas bubbles, X-ray radiography, and FTIR or EDXRF signatures. Origin calls can remain inconclusive, so the finding should be issued by a qualified gem laboratory.
Evidence grade AScope: Applies where natural, synthetic and treated corundum, and geographic origin, must be assessed; no self-administered criteria are given.
Sources G&G Summer 1998 · G&G Winter 2019 · G&G Fall 2019 +2
- Separating Natural and Synthetic Rubies on the Basis of Trace-Element Chemistry (Gems & Gemology, Summer 1998, Vol. 34, No. 2)
- Geographic Origin Determination of Ruby (Gems & Gemology, Winter 2019, Vol. 55, No. 4)
- Cobalt-Coated Sapphire (Lab Notes, Gems & Gemology, Fall 2019, Vol. 55, No. 3)
- Translucent Ruby Filled with Zinc Glass (Lab Notes, Gems & Gemology, Fall 2023, Vol. 59, No. 3)
- Bismuth Glass-Filled Burmese Star Ruby (Lab Notes, Gems & Gemology, Spring 2020, Vol. 56, No. 1)
Origin labels for color-change sapphire (Sri Lanka and elsewhere, for instance) are often used to support a premium, yet origin cannot be inferred from appearance or name. Origin determination is a comparison against reference databases of known localities: a laboratory measures trace-element suites by LA-ICP-MS and weighs inclusion features such as rutile silk, clouds, and growth zoning against specimens of documented provenance. The judgement is relative - the characteristic ranges of different localities overlap, deposits with no reference material cannot be assigned, and a single deposit is internally variable; heating and other treatments alter the measurable features, so treatment status must be settled first, and an individual stone may therefore return an "inconclusive" result. An origin call must be issued by an accredited laboratory for a specific specimen, and "consistent with a locality" is not the same as "mined there".
Evidence grade AScope: Origin cannot be inferred from appearance or name; conclusions are probabilistic and must be issued by an accredited laboratory for a specific specimen; no self-test criteria are given here.
Other research findings
A color-change gem is usually defined as one whose hue changes by more than one adjacent hue position (e.g. blue to red, or green to red).
Evidence grade AScope: A conventional definition of the term, distinguishing pronounced color change from slight tint shifts under ordinary lighting.
Limits of this research
- Research status: Formation, occurrence or other material-specific findings found in authoritative sources
- The mechanism is illustrated chiefly with a vanadium-colored (V3+) synthetic color-change sapphire; natural color-change sapphire may have more complex chromophore combinations (including chromium).
- The cited source reports color differences under typical light sources (D65 daylight, A incandescent); actual strength also depends on cut orientation and source spectrum.
- No absolute timescale for color-change sapphire is given by the cited sources.
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
- Colour-change Sapphire
GB/T 16552—2017 5.3.3 · IMA Mineral List 2026-07 “Corundum”
Construction or treatment status
Natural identity; treatment status unknown
Treatments recorded for this material: Heated / Heat-treated (via parent material), Dyed (via parent material), Filled / Fracture-filled (via parent material), Diffusion-treated (via parent material), Irradiated (via parent material)
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
Colour-change Sapphire is Sapphire (corundum) showing colour change under different light sources; use "Colour-change Sapphire" for listings, and disclose any known treatments.
Evidence
- GB/T · 5.3.3
What this means for you
Before buying, check the recommended listing name "Colour-change Sapphire" 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
The item-by-item care advice that the GIA Care and Cleaning Guide gives for the whole class, and so for Colour-change Sapphire, is set out in full under care on the Sapphire entry.
Care
Each row's “Source & check” expands to the full source; the date beside it is the fact check date.
Durability and wearing
Toughness
Excellent
Sources GIA Gem Encyclopedia (care guide)
Daily wear
Colour-change sapphire is corundum at Mohs 9 with excellent toughness and no cleavage, a great choice for daily wear; the main risks come from treatments — filled/dyed stones are harmed by even mild acids like lemon juice, and shallow lattice-diffused colour can be removed by surface damage or re-cutting.
Care
Warm soapy water is always safe; ultrasonic and steam cleaning are usually safe for untreated, heat-treated and lattice-diffusion treated sapphire; fracture-filled, cavity-filled or dyed material should be cleaned only with a damp cloth; boric acid powder will etch the surface of even untreated stones.
Sources GIA Gem Encyclopedia (care guide)
Scope: This field describes general material properties and does not constitute a durability or safety warranty for any specific finished product; the durability of treated (filling/dyeing/coating) or assembled pieces must be assessed separately.
Treatments and identification leads
One row per treatment, with three standards side by side: how often it occurs and how stable it is (CIBJO), its category in GB/T 16552—2017 Table B.1 (this site's paraphrase) and how the JJA/AGL 2025 table lists it. Each CIBJO value links to its entry under “Testing and market”, where the wording and source are given in full.
This table scrolls sideways on narrow screens.
| Treatment | Market frequency (CIBJO) | Stability (CIBJO) | GB/T 16552 category | JJA/AGL listing | Identification leads |
|---|---|---|---|---|---|
| Heating | — | — | Optimization | — | — |
| Dyeing | — | — | Treatment | — | — |
| Filling | — | — | Graded — see §5.4.1, Table 1 | — | — |
| Diffusion | — | — | Treatment | — | — |
| Irradiation | — | — | Treatment | — | — |
“—” means the cited source gives no value for that item, not “none”. Source: GB/T 16552—2017 Table B.1 (row for Sapphire)
Whether a treatment has to show in the name differs between the two rule sets (this site’s paraphrase):
- GB/T 16552—2017: a method classed as treatment has to be stated in the name itself — the method put before the name, or added in brackets after it; a method classed as optimization does not need to appear in the name, though one marked “Optimization (annotation required)” still has to be noted in the quality documents. Source: §5.4.2.1 a), b); §5.4.2.2 a)
- CIBJO Gemstone Book 2022: no longer splits treatments into ones that need specific disclosure and ones that need only general disclosure: every treatment is to be disclosed, and the seller tells the buyer which treatment was used and what special care it calls for. Source: §4.2.5 Note 2, §4.2.5.1, pp.14–15
What this table covers
What this page can give
- Registered treatments, their stability and how often they occur (see the table above)
- Identification leads for each treatment, for use when sending a stone for testing
How lab reports word it
Report wording for Colour-change Sapphire is set out under report wording on the Corundum entry.
A general LMHC wording rule also covers Colour-change Sapphire (Information Sheet #9): see the LMHC rule “Colour-change stones”.
VerifyNames, standards, technical facts, clauses and sources
Names
For Colour-change Sapphire, "alexandrite sapphire" must not be used as a name (CIBJO Gemstone Book 2022 §4.2.4.5; GB/T 16552—2017 §5.1.2.1 c)); one further name in a non-Latin script is listed in the name register below (1 that must not be used as a name).
Standard and listing namesThe formal name of Colour-change Sapphire is built under the naming rules of GB/T 16552—2017; the standard does not list this name separately, and it is built on Sapphire as the base name. The suggested listing name is Colour-change Sapphire. Names in four languagesThe four-language names are the Simplified and Traditional Chinese names, English Colour-change Sapphire and the Japanese name. Institution usageFor authority wording, CIBJO records Colour-change Sapphire (CIBJO Gemmological Laboratories Book 2024); the FTC text on file has no wording for this name, which has been checked; GIA and Gem-A are not yet checked; bodies without a recorded wording show the entry's own English name, which does not represent their position. Japanese namesThe entry carries its own Japanese name, but the GSJ (Japan) wording for this name is not yet verified by this site. Candidate search termsThe English alexandrite sapphire and its Chinese equivalent are recorded as market names, as search candidates only and not to be used as names: the CIBJO Gemstone Book 2022 lists alexandrite sapphire verbatim as a prohibited combination of gem names, and GB/T 16552—2017 gives naming by combining two or more natural gem names as a counter-example; the correct form is Colour-change Sapphire.
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 |
|---|---|---|---|---|
| not to be used as a name (2) | ||||
| alexandrite sapphireEnglish | market name | search candidate only | not to be used as a name | CIBJO Gemstone Book 2022 4.2.4.5; GB/T 16552—2017 5.1.2.1 c); Note: CIBJO Gemstone Book 2022 §4.2.4.5 lists this combination of gem names, word for word, as one that shall not be used. |
| 变石蓝宝石Simplified Chinese | market name | search candidate only | not to be used as a name | GB/T 16552—2017 5.1.2.1 c); GB/T 16552—2017 5.3.3; Note: GB/T 16552—2017 §5.1.2.1 c) uses it as the example of a rule: the names of two or more natural gems must not be combined to name one gem (a counter-example, not a trade name); the standard form is colour-change sapphire (§5.3.3). |
How each authority words this name: see Names › Authority wording.
- GSJ (Japan) formal name
- カラーチェンジ・サファイア (not yet checked for this body — the entry's own Japanese name is shown)
- Name built by the GB/T naming rules (not listed as such)
- 变色蓝宝石 (GB/T 16552—2017 §5.3.3; basic name 蓝宝石)
- Mineralogical name
- Sapphire (corundum) showing colour change under different light sources
- Trade names and synonyms
- Not to be used as a name: alexandrite sapphire (market name)
Four-language names
- 简体中文
- 变色蓝宝石
- 繁體中文
- 變色藍寶石
- English
- Colour-change Sapphire
- 日本語
- カラーチェンジ・サファイア
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
Colour-change Sapphire is covered in GB/T 16552—2017 Annex B, Table B.1 by this site applying the "Sapphire" row: heat treatment is listed as optimization; dyeing as treatment; diffusion as treatment; irradiation as treatment; and filling is graded under Table B.1, with each grade defined on the Gem treatments page. The full row with the effect column is on the Sapphire page; the explanation of Table B.1 is on the Gem treatments page.
GB/T 16552-2017, Annex B, Table B.1
Under the “Sapphire” row of Table B.1: Heating Optimization; Dyeing Treatment; Filling Graded — see §5.4.1, Table 1; Diffusion Treatment; Irradiation Treatment. The full row, with the effect column, is on the Sapphire page.
What Table B.1 is, and how the “see 5.4.1” grades are defined: see the GB/T 16552: optimization vs treatment page.
What it is and how it's identified
The composition (phase) of Colour-change Sapphire is corundum. For the structure, hardness, cleavage, density, optical character, refractive index and lustre of Colour-change Sapphire, the cited clause gives values for sapphire as a whole (regardless of colour and origin), not measured on Colour-change Sapphire alone. Values for sapphire as a whole (regardless of colour and origin): structure crystalline, trigonal; Mohs hardness 9, no cleavage, though stones with well-developed twinning may show three directions of parting; optical character anisotropic, uniaxial, negative; birefringence 0.008–0.01; density 3.95–4.1 g/cm³ (clause value 4.00, permitted tolerance +0.10/−0.05, range derived from this); refractive index 1.757–1.779 (clause value 1.762–1.770, permitted tolerance +0.009/−0.005, range derived from this); the colour-change effect can occur; untreated, pleochroism is strong and varies with body colour, and 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”.
Chemical composition, luminescence, UV-visible spectrum, infrared spectrum, magnification: these whole-class features are given in the cited clause for sapphire as a whole (all colours and origins), so they are not repeated on the Colour-change Sapphire page; see the material facts on the Sapphire entry.
Items below that name the class they cover give the cited clause’s value for that whole class, not a measurement of Colour-change Sapphire (how to read class-level values).
Definition
Colour-change Sapphire — composition (phase): corundum
CIBJO Gemmological Laboratories Book 2024
Source & check 2026-09-22
- Source
- Fact checked on
- 2026-09-22
Structure
Colour-change Sapphire — structure (overall): crystalline
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- sapphire as a whole (all colours and origins)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.3 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Colour-change Sapphire — structure (crystal system): trigonal
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- sapphire as a whole (all colours and origins)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.3 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Colour-change Sapphire — structure (crystal habit): hexagonal prisms or barrel shapes, occasionally tabular or bladed.
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- sapphire as a whole (all colours and origins)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.3 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Durability
Colour-change Sapphire — Mohs hardness: 9
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
- What this covers
- sapphire as a whole (all colours and origins)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.3 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Colour-change Sapphire — cleavage: no cleavage; stones with well-developed twinning may show parting in three directions.
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- sapphire as a whole (all colours and origins)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.3 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Physical properties
Colour-change Sapphire — density: 3.95–4.1 g/cm³
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- sapphire as a whole (all colours and origins)
- Qualification
The clause we cite gives 4.00, with a stated tolerance of +0.10 / -0.05. The range shown here is worked out from that.
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.3 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Optical
Colour-change Sapphire — optic character: uniaxial, optically negative (anisotropic)
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- sapphire as a whole (all colours and origins)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.3 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Colour-change Sapphire — refractive index: 1.757–1.779
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- sapphire as a whole (all colours and origins)
- Qualification
The clause we cite gives 1.762–1.770, with a stated tolerance of +0.009 / -0.005. The range shown here is worked out from that.
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.3 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Colour-change Sapphire — birefringence: 0.008–0.01
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- sapphire as a whole (all colours and origins)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.3 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Colour-change Sapphire — pleochroism: strong, and varying with color: blue shows blue and green-blue; green shows green and yellow-green; yellow shows yellow and orange-yellow; orange shows orange and orange-red; pink shows pink and pink-red; purple shows purple and purple-red.
GB/T 16553—2017
- Treatment state
- untreated
- Does this standard apply
- applies to this entry
- What this covers
- sapphire as a whole (all colours and origins)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.3 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Colour-change Sapphire — fluorescence (overall): violet and colour-change: long wave none to strong, red; short wave none to weak, red.
GB/T 16553—2017
UV fluorescencerednone–strong, violet and colour-changerednone–weak, violet and colour-changeDots are illustrative colours built from the colour names, not measured values
- Treatment state
- untreated
- Does this standard apply
- applies to this entry
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.3 Fluorescence (locator checked 2026-09-28)
- Fact checked on
- 2026-09-26
Colour-change Sapphire — spectrum (UV-visible): pink, violet and colour-change sapphire: shows the absorption bands of ruby and of blue sapphire.
GB/T 16553—2017
- Does this standard apply
- applies to this entry
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.3 UV-visible spectrum (locator checked 2026-09-28)
- Fact checked on
- 2026-09-26
Colour-change Sapphire — optical effect (asterism): seen; commonly a six-rayed star
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- sapphire as a whole (all colours and origins)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.3 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
optical effect (colour change)2 sources compared
Colour-change Sapphire — optical effect (colour change): colour change.
CIBJO Gemmological Laboratories Book 2024
Source & check 2026-09-22
- Source
- Fact checked on
- 2026-09-22
Colour-change Sapphire — optical effect (colour change): seen
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- sapphire as a whole (all colours and origins)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.3 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Colour-change Sapphire — body colour: Blue (daylight) to violet or purple (incandescent) variety of corundum; many other colour changes are possible.
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 Alexandrite and Colour-Change Garnet.
- General note
- colour alone is not identity
Source & check 2026-09-22
- Source
- Fact checked on
- 2026-09-22
- CIBJO definitions
- asterism, colour change
Quality factors
Colour-change Sapphire — quality factor (lustre): vitreous to subadamantine
GB/T 16553—2017
- Treatment state
- untreated
- Does this standard apply
- applies to this entry
- What this covers
- sapphire as a whole (all colours and origins)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.3 (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.
This material (RI / SG midpoints): 1.768 / 4.03; Closest values: 1Rhodolite 1.755 / 3.9, 2Almandine 1.79 / 3.9, 3Grossular 1.745 / 3.9, 4Tsavorite 1.74 / 3.9, 5Spessartine 1.802 / 3.9
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
The basis for distinguishing Colour-change Sapphire from other varieties is that the dominant hue in daylight must differ from the dominant hue under incandescent light; for comparison, daylight is taken as 5500–6500 K and incandescent light as 2700–3600 K, and the registered treatment status is untreated. CIBJO's laboratory rules place colour-change sapphire under sapphire; identification is covered in the sapphire entry, and the list of required methods is on the laboratory testing page.
The CIBJO laboratory protocol covers Colour-change Sapphire under “Sapphire” (§6.1.69): see identification on the Sapphire entry; the required tests are listed on the CIBJO laboratory protocol table for Sapphire.
How far testing can go
Colour-change Sapphire — 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
Each row's “Source & check” expands to the full source; the date beside it is the fact check date.
Clause-level definitions
Colour-change Sapphire has a clause-level definition in CIBJO Gemmological Laboratories Book 2024 under the term Colour-change sapphire. The definition gives the mineral species corundum and the mineral/gem variety colour-change sapphire, noting that the CIBJO wording is quoted in full under Clause-level definitions on this page. The cross-check shows it is defined directly by CIBJO, and no identically named English entry was found in this edition of the GB/T annex.
This table scrolls sideways on narrow screens.
| Term | Clause | Definition | Cross-check |
|---|---|---|---|
| Colour-change sapphire | 7.2.1.64 | Blue (daylight) to violet or purple (incandescent) variety of corundum; many other colour changes are possible | Defined directly by CIBJO; no identically named English entry was found in this edition of 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
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.
Related-entry tree for Corundum on this site: 18 entries listed by this site's parent-entry links; synthetic, treated and similar entries carry their recorded state after the name; this page (Colour-change Sapphire) is marked.
- Corundum
Sub-entries (13)
- Colour-change Sapphire
- Green Sapphire
- Orange Sapphire
- Padparadscha Sapphire
- Pink Sapphire
- Purple Sapphire
- Ruby
Sub-entries (2)
- Lead-Glass-Filled Ruby
- Synthetic Ruby (Synthetic product)
- Sapphire
Sub-entries (2)
- Beryllium-Diffused Sapphire
- Synthetic Sapphire (Synthetic product)
- Star Ruby
- Star Sapphire
- Synthetic Corundum (Synthetic product)
- White Sapphire
- Yellow Sapphire
This table scrolls sideways on narrow screens.
| Page | Content | Status |
|---|---|---|
| Browsing family | Oxide minerals | Live |
| Treatments recorded for this material | Heated / Heat-treated (via parent material), Dyed (via parent material), Filled / Fracture-filled (via parent material), Diffusion-treated (via parent material), Irradiated (via parent material) | Live |
| Related articles | To be added (placeholder) | Planned |
Who maintains this page
The material facts in the Colour-change Sapphire 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.