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Natural inorganic gem materials · Mineral / gemstone variety · Natural; common industry optimization (verify with certificate)

Sapphire

Also known asFancy sapphire

The collective name for gem Corundum other than Ruby; under GB/T 16552-2017 clause 5.1.2.1, place of origin should not form part of the name. 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.

Edited by JuneReviewed by RalphLast updated 2026-10-13Who maintains this page

FAQCare and wear

Questions people ask about Sapphire

Every sentence below is followed by the registered fact it rests on; answers add no new facts and promise no outcome.

Q1Is sapphire always blue, and what makes it blue?

No: sapphire is gem corundum of any colour other than ruby, and its blue is caused jointly by iron (Fe2+) and titanium (Ti4+).G&G Winter 2019Its recorded colours include blue, blue-green, green, yellow, orange, pink, purple, black, grey and colourless.GB/T 16553—2017A colour-change effect is also recorded in sapphire.GB/T 16553—2017Its pleochroism is strong and varies with colour; a blue stone, for example, shows blue and green-blue.GB/T 16553—2017

Q2Can you tell a natural sapphire from a lab-grown one or glass by looking?

Not reliably: a sapphire's appearance cannot reliably indicate its naturalness, and stones of similar colour may differ in genesis and chemistry.G&G Winter 2019According to the parent entry Corundum, a synthetic counterpart is commercially available.CIBJO Gemstone Book 2022 (via parent entry Corundum)The parent entry Corundum also records that corundum can be confused by colour, even with other gems, and that appearance plus a single measurement is not always enough.G&G Fall 2019 (via parent entry Corundum)Glass imitations exist: in one laboratory case, blue star cabochons were glass with a specific gravity of about 2.46, a refractive index of 1.40 and a moulded star fixed in place.G&G Fall 2021Whether one particular bead is natural, treated or synthetic — only a laboratory report can settle that.What this page can answer

Q3Is sapphire durable enough for an everyday ring?

Yes: corundum is Mohs 9 with excellent toughness and no cleavage, which makes sapphire well suited to rings and other jewellery worn every day.GIA Gem Encyclopedia (care guide)It has no cleavage, though stones with well-developed twinning may show parting in three directions.GB/T 16553—2017Prong, bezel, flush, channel and pavé settings are all rated relatively safe, while stones with pronounced twinning, fractures or many inclusions need extra care.Gems & Gemology 1987 (Martin)Stones filled with high-lead glass, however, carry treatment-related durability concerns.GIA Gem Encyclopedia (care guide)

Q4How are sapphires treated, and which treatments need extra care?

Sapphires heated to create, deepen or lighten colour, or to improve uniformity, need normal care, though repolishing or recutting should be avoided when the effect lies near the surface.AGTA Gemstone Information Manual, 17th ed.In lattice-diffused sapphire the colour penetrates to varying depths, and where the coloured layer is shallow, surface damage or recutting can remove the colour.GIA Gem Encyclopedia (care guide)For glass-filled sapphire, GIA notes that fractures today are filled mainly with high-lead glass, and such stones need more care than untreated, heated or diffused ones, because many chemicals, even lemon juice, can damage or alter the glass.GIA Gem Encyclopedia (care guide)Irradiation can turn colourless, light yellow and some light blue sapphire deep yellow or orange-yellow, but that colour is not stable and the treatment is hard to detect.GB/T 16553—2017Whether one particular bead is natural, treated or synthetic — only a laboratory report can settle that.What this page can answer

Q5How should you clean a sapphire ring, and is an ultrasonic cleaner safe?

Warm soapy water is safe at any time.GIA Gem Encyclopedia (care guide)Ultrasonic and steam cleaners are usually safe, including for heat-treated and lattice-diffused stones.GIA Gem Encyclopedia (care guide)Fracture-filled, cavity-filled or dyed sapphires should be cleaned only with a damp cloth.GIA Gem Encyclopedia (care guide)Boric acid powder etches the surface even of untreated stones.GIA Gem Encyclopedia (care guide)

Q6Does a name like Kashmir or Ceylon sapphire prove where it came from?

No: a locality name such as Kashmir, Ceylon, Burma, Madagascar or Mozambique is only a trade attribution, not a determined origin.G&G Winter 2019 · G&G Summer 1998 +2Origin is determined in a laboratory from inclusion scenes and trace-element chemistry, checked against reference data, and origin calls carry uncertainty.G&G Winter 2019Heating, filling and diffusion alter the measurable features, so they must be ruled out first.G&G Winter 2019 · G&G Summer 1998 +2

Q7How do sapphires form?

Sapphire deposits are of magmatic and metamorphic types; magmatic sapphire is mostly carried up as crystals in alkali basalt and concentrated into placers.G&G Winter 2019Metamorphic sapphire commonly needs metasomatic fluids infiltrating aluminium-rich rocks, and metamorphic corundum generally forms at about 500–800°C.G&G Winter 2019 · G&G Summer 2023Surface weathering concentrates the weathering-resistant corundum into placers.G&G Winter 2019 · G&G Summer 2023Four main periods of corundum formation are recognised, from the Archean, about 2.97 Ga, to Cenozoic alkali-basalt eruption, 65 Ma to the Quaternary.G&G Winter 2019

Q8What makes a good-quality sapphire?

According to GIA, colour has the greatest influence on sapphire quality: the most favoured blue sapphires are velvety blue to violetish blue, in medium to medium-dark tones, with strong to vivid saturation.GIA Sapphire Quality FactorsIn general, the more intense and even the colour, the more highly a sapphire is rated.GIA Sapphire Quality FactorsBlue sapphires usually contain some inclusions, though generally fewer than rubies, and blue sapphires of extremely high clarity are rare.GIA Sapphire Quality FactorsFor star sapphires, the parent entry Corundum records that the best stones show a crisp, distinct star against strongly saturated colour.GIA Sapphire Quality Factors (via parent entry Corundum)

Q9What is a padparadscha sapphire?

Laboratories in the LMHC define padparadscha as corundum of any origin showing a delicate blend of pinkish-orange and orange-pink hues, pastel in tone, and require a colour-stability test for any stone of that colour.LMHC Information Sheet #4The name is not used for stones that have been irradiated, dyed, coated, painted, varnished or sputtered.LMHC Information Sheet #4

Q10What does sapphire symbolize, and does it have healing powers?

There is no scientific evidence that sapphire has healing powers: the UK advertising regulators ASA and CAP state that they have not seen evidence that crystal therapy can treat medical conditions.ASA/CAP guidance (UK)Its recorded cultural role is as the September birthstone: Jewelers of America and Japan's JJA list it for September, and the U.K. National Association of Jewellers lists blue sapphire as traditional for September.Cultural recordsMuseum collections show early datable sapphire settings in 5th–7th-century Byzantine goldwork, continued in medieval English, Iranian and European rings.The Met 52.7 · The Met 17.190.145 +4

What this page can answer

This page covers

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

Sapphire is the collective name for gem-quality corundum of any colour other than red, with blue caused jointly by iron (Fe2+) and titanium (Ti4+). Corundum is a high-temperature mineral forming mainly under amphibolite- to granulite-facies conditions (~500-800°C) in alumina-rich rocks. Sapphire deposits are divided into magmatic and metamorphic types: magmatic examples include sapphire in continental alkali basalts, mostly carried to the surface as xenocrysts/megacrysts and concentrated into eluvial/alluvial placers by tropical weathering (e.g. Australia, Southeast Asia); metamorphic examples occur in mafic-ultramafic rocks, marble, gneiss and metapelite, with Kashmir's prized sapphire hosted in desilicated pegmatite (plumasite) in M-UMR, its velvety blue being caused by layers of microscopic fluid inclusions; metamorphic sapphire commonly requires metasomatic fluids infiltrating Al-rich protoliths. Deposit models must not be generalised: host rocks and fluid conditions differ by locality.

Scope: Covers gem-quality corundum of all colours other than ruby; the specific colour and deposit type must be stated, and the model for one locality must not be extended to all.

Sources G&G Winter 2019 · G&G Summer 2023

Where it forms

Magmatic type: continental alkali basalt/lamprophyre, sapphire as xenocrysts or megacrysts.

Sources G&G Winter 2019

Metamorphic type: mafic-ultramafic rocks, marble, gneiss, metapelite, at amphibolite- to granulite-facies.

Sources G&G Winter 2019

Metamorphic-metasomatic type: desilicated pegmatite (plumasite) and skarn, with high water-rock interaction.

Sources G&G Winter 2019

How it forms, step by step

  1. Alumina-rich protoliths are heated and pressurised during orogenic metamorphism or magmatism.

    Sources G&G Winter 2019 · G&G Summer 2023

  2. Corundum crystallises at amphibolite- to granulite-facies (or magmatic) conditions; metamorphic sapphire may involve metasomatic fluids.

    Sources G&G Winter 2019 · G&G Summer 2023

  3. Magmatic sapphire is carried upward as xenocrysts/megacrysts in basaltic magma.

    Sources G&G Winter 2019 · G&G Summer 2023

  4. Surface weathering concentrates weathering-resistant corundum into eluvial/alluvial placers.

    Sources G&G Winter 2019 · G&G Summer 2023

Link to appearance

The blue comes from Fe2+-Ti4+ charge transfer; Kashmir sapphire's velvety look derives from layers of microscopic fluid inclusions, which also record formation conditions.

Sources G&G Winter 2019

Timescale

Four main periods of corundum formation are recognised, from the Archean (~2.97 Ga) to Cenozoic alkali-basalt eruption (65 Ma to Quaternary).

Sources G&G Winter 2019

Related base materials

  • Corundum: Mineral parent: sapphire is the collective name for gem corundum of all colours other than ruby
  • Ruby: The red variety of the same species (corundum); its name is mutually exclusive with sapphire

Supporting findings

Sapphire deposits divide into magmatic and metamorphic types; magmatic sapphire is mostly xenocrysts/megacrysts in alkali basalt concentrated into placers.

Evidence grade A

Scope: Describes the magmatic type; metamorphic localities differ and must not be conflated.

Sources G&G Winter 2019

Kashmir's prized blue sapphire is hosted in desilicated pegmatite in M-UMR, its velvety blue caused by layers of microscopic fluid inclusions.

Evidence grade A

Scope: Specific to the Kashmir locality model and not extensible to other sources.

Sources G&G Winter 2019

Metamorphic sapphire commonly requires metasomatic fluids infiltrating Al-rich protoliths; metamorphic corundum generally forms at amphibolite- to granulite-facies (~500-800°C).

Evidence grade A

Scope: General conditions for metamorphic sapphire; individual P-T and fluid sources require case-by-case verification.

Sources G&G Winter 2019 · G&G Summer 2023

There are four main periods of corundum formation, spanning the Archean to the Cenozoic, each corresponding to different tectonic settings.

Evidence grade A

Scope: A global periodisation and not a basis for dating any single locality.

Sources G&G Winter 2019

Recorded localities

Authoritative sources list the localities below; the list is not exhaustive.

Locality sketch mapLand outlines only; the map does not depict any national or regional boundary. Dots mark approximate positions. Base map: Natural Earth (public domain).

Africa

Asia

North America

Oceania

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

Sapphire is gem corundum of any colour other than ruby, with blue caused jointly by iron (Fe2+) and titanium (Ti4+).

Evidence grade A

Scope: Concerns blue coloration; other coloured sapphires differ and must have their colour specified.

Sources G&G Winter 2019

Where the name comes from

Laboratories in the LMHC define padparadscha sapphire as corundum, from any geographical origin, showing, in standard daylight, a delicate blend of pinkish-orange and orange-pink hues, pastel in tone and low to medium in saturation. For any corundum of padparadscha-like colour, a colour-stability test is mandatory.

Evidence grade A

Scope: Describes how the cited standard or laboratory body defines the name; trade usage and other bodies may differ, and whether a given stone qualifies can only be decided by laboratory testing.

Sources LMHC Information Sheet #4

The LMHC does not apply the name padparadscha sapphire to a stone that has been treated by irradiation, or that has been dyed, coated, painted, varnished or sputtered.

Evidence grade A

Scope: Describes how the cited standard or laboratory body defines the name; trade usage and other bodies may differ, and whether a given stone qualifies can only be decided by laboratory testing.

Sources LMHC Information Sheet #4

Human use and museum objects

The collection evidence shows early datable sapphire settings in 5th-7th-century Byzantine goldwork (Met 52.7, 17.190.145), continued in medieval English, Iranian and European rings (Met 2015.697, 1994.40, 52.32.4; Cleveland 1950.383); the evidence pertains to the corundum parent material, not to this name uniquely.

Evidence grade A

Scope: Applies to collection rings and earrings recorded as sapphire (gem corundum other than ruby) from Byzantium, Europe and West Asia; the evidence pertains to the corundum parent material.

Sources The Met 52.7 · The Met 17.190.145 · The Met 2015.697 +3

Objects recorded as sapphire in these collections are mostly rings and earrings and cluster in date. Among the earlier are a 5th-6th-century Byzantine gold finger ring with a sapphire intaglio (Met 52.7) and 6th-7th-century Byzantine gold earrings with pearls and sapphires (Met 17.190.145). From medieval Europe come a late 13th- or early 14th-century gold stirrup ring (Met 2015.697), a 14th-century gold finger ring (Met 1994.40) and a 14th-century English gilded-silver sapphire ring (Cleveland 1950.383). Also present are an 11th-13th-century Iranian gold-sheet ring (Met 52.32.4) and a star-sapphire brooch with an emperor intaglio of about 950-1000 (Met 1988.15; Ottonian setting, Byzantine intaglio). Sapphire is the collective name for gem corundum other than ruby; this record is not an independent material and the evidence pertains to the corundum parent material. Design watercolours (e.g. Met 1980.1013.21) are not objects and are not counted.

Sources The Met 52.7 · The Met 17.190.145 · The Met 1988.15 +4

Scope: A museum object evidences only the existence and date of that artefact itself; it does not establish widespread ancient use of the material, nor does it attest the origin, naturalness, or treatment of any modern specimen.

Objects cited

400600800100012001400Met 52.75th–6th centuryMet 17.190.1456th–7th centuryMet 52.32.411th–13th centuryCMA 1950.3831300sMet 1994.4014th century
Dates of museum objectsDates from the museums' open-access records (CC0); each bar spans the whole period named in the record, with qualifiers such as “early” or “possibly” kept in the label rather than turned into a narrower range; an arrow marks a record that reads “before” or “after” a yearSource: The Met / Cleveland Museum of Art open-access records
  • The Met 52.7Finger Ring · 5th–6th century · ByzantineGold, with niello & sapphire intaglio
  • The Met 17.190.145Gold Earring with Pearls and Sapphires · 6th–7th century · ByzantineGold, sapphire, pearls
  • The Met 1988.15Brooch with Intaglio of an Emperor · ca. 950–1000 (setting); 337–50 (intaglio) · Ottonian (Rhineland (?)) (setting); Byzantine (intaglio)Star sapphire, pearls, gold
  • The Met 52.32.4Ring · 11th–13th century · IranGold sheet and sapphire
  • The Met 2015.697Stirrup Ring · late 13th or early 14th century · BritishGold and sapphire
  • The Met 1994.40Finger Ring · 14th century · BritishGold and sapphire
  • Cleveland Museum of Art 1950.383Ring · 1300s · England, 14th centurygilded silver, sapphire

Cultural records for this material: Birthstone list.

How it is identified

A sapphire's appearance cannot reliably indicate its geographic origin or naturalness; stones of similar colour may differ in genesis and chemistry. Origin determination is done in a laboratory from inclusion scenes and trace-element chemistry, using instruments such as laser ablation inductively coupled plasma mass spectrometry to measure trace elements and Raman spectroscopy to identify inclusions, checked against reference data. Origin calls carry uncertainty and must be issued by an accredited laboratory.

Evidence grade A

Scope: Origin determination is a laboratory conclusion that relies on reference data and carries uncertainty, to be issued by an accredited body.

Sources G&G Winter 2019

Sapphire is often priced on locality, with goods traded under names such as Kashmir, Ceylon, Burma, Madagascar or Mozambique. A locality name, however, is only a trade attribution and is not a determined origin. Origin work is a laboratory exercise: the deposit type is addressed first, then inclusion suites and trace-element suites (measured by methods such as laser ablation ICP-MS) are compared with reference databases for known localities to yield a conclusion of consistency or inconsistency with a source. Because the characteristic ranges of different localities overlap and vary within a single deposit, the conclusion is probabilistic and may be only inconclusive; heating, filling and diffusion alter the measurable features and must be excluded first. Origin cannot be inferred from appearance or name; an origin conclusion must be issued by a qualified laboratory for a specific specimen. This entry offers no self-test criteria or thresholds.

Evidence grade A

Scope: Origin cannot be inferred from appearance or name; an origin conclusion must be issued by a qualified laboratory for a specific specimen, and this entry provides no self-test criteria or thresholds.

Sources G&G Winter 2019 · G&G Summer 1998 · G&G Spring 2015 +1

In one laboratory case, blue cabochons with a six-rayed star resembling star sapphire were manufactured glass. Their specific gravity averaged 2.46 and refractive index was 1.40, and the star had been moulded in and was fixed in place rather than being genuine asterism.

Evidence grade A

Scope: Describes identification features reported by a laboratory or educational source; it is not a test that a reader can rely on, and any single piece can only be identified by a gemmological laboratory.

Sources G&G Fall 2021

Other research findings

Colour has the greatest influence on sapphire quality. The most favoured blue sapphires are velvety blue to violetish blue in medium to medium-dark tones, with strong to vivid saturation; in general, the more intense and even the colour, the more highly a sapphire is rated.

Evidence grade B

Scope: Quality factors as described by one educational source; not a grading standard and not a statement about the value of any piece.

Sources GIA Sapphire Quality Factors

Blue sapphires usually contain some inclusions, though generally fewer than rubies; blue sapphires of extremely high clarity are rare.

Evidence grade B

Scope: Quality factors as described by one educational source; not a grading standard and not a statement about the value of any piece.

Sources GIA Sapphire Quality Factors

Limits of this research

  • Research status: Formation, occurrence or other material-specific findings found in authoritative sources
  • Sapphire spans many colours other than red; without a stated colour, genesis and appearance descriptions must be cautious.
  • Metamorphic source models (Kashmir, Sri Lanka, Madagascar, etc.) differ and must not be generalised.
  • Synthetic sapphire and heat/diffusion treatments are outside this formation layer.

Methodology

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
Sapphire

GB/T 16552—2017 Table A.1 “Sapphire” · IMA Mineral List 2026-07 “Corundum”

Construction or treatment status

Natural; common industry optimization (verify with certificate)

Treatments recorded for this material: Heated / Heat-treated, Diffusion-treated, Dyed, Filled / Fracture-filled, Irradiated

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

Sapphire is often subjected to heating and diffusion. Under GB/T 16552-2017, heating counts as an optimization, so the plain gem name may be used (§5.4.2.1 a); diffusion counts as a treatment and must be stated in the name (§5.4.2.2 a). Do not assume it is unenhanced.

Evidence

  • GB/T · Table A.1, row 蓝宝石 (Sapphire)

What this means for you

Before buying, check the recommended listing name "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

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)3 sources compared

Sapphire — care (cleaning): ultrasonic and steamer: use caution; note: polishing compound can get into inclusions or fractures that reach the surface.

Gems & Gemology 1987 (Martin)

Treatment state
untreated
Source & check 2026-09-26
Source
Fact checked on
2026-09-26

Sapphire — care (cleaning): Ultrasonic and steam cleaners are usually safe, and the same holds for heat-treated and lattice-diffused stones.

GIA Gem Encyclopedia (care guide)

Treatment state
untreated
Source & check 2026-09-26
Source
Fact checked on
2026-09-26

Sapphire — care (cleaning): Cleaning with warm soapy water is safe at any time

GIA Gem Encyclopedia (care guide)

Treatment state
any treatment state
Source & check 2026-09-26
Source
Fact checked on
2026-09-26

Sapphire — 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
Colours covered
blue sapphire only
Only after these treatments
fissure filling with oil, fissure filling with resin
Source & check 2026-09-25
Source
Fact checked on
2026-09-25

Sapphire — care (cleaning): Fracture-filled, cavity-filled or dyed material should be cleaned only with a damp cloth.

GIA Gem Encyclopedia (care guide)

Treatment state
treated
Only after these treatments
dyeing, filling
Source & check 2026-09-26
Source
Fact checked on
2026-09-26

Sapphire — care (cleaning): oiled or dyed stones: avoid solvents.

Gems & Gemology 1987 (Martin)

Treatment state
treated
Only after these treatments
dyeing, fissure filling with oil
Source & check 2026-09-26
Source
Fact checked on
2026-09-26

Sapphire — care (light): Some stones fade rapidly unless kept in the dark.

CIBJO Gemstone Book 2022

CIBJO Gemstone Book §6.2:special-care code g

Treatment state
treated
Only after these treatments
irradiation
Applies only to
other colours, sold under a colour prefix
Source & check 2026-09-26
Source
Fact checked on
2026-09-26

care (chemicals)2 sources compared

Sapphire — care (chemicals): Glass, plastic or hardened-resin fillers in cavities or fractures can be scratched more readily than the stone around them, or be more easily damaged by heat or some acids (e.g. hydrofluoric); keep it away from all chemicals, heat and abrasives.

CIBJO Gemstone Book 2022

CIBJO Gemstone Book §6.2:special-care code l

Treatment state
treated
Colours covered
blue sapphire only
Only after these treatments
filling, flux-assisted healing
Source & check 2026-09-25
Source
Fact checked on
2026-09-25

Sapphire — care (chemicals): stable in normal wear and not easily harmed by heat, light or common chemicals, though boric acid powder etches the surface even of untreated stones.

GIA Gem Encyclopedia (care guide)

Treatment state
untreated
Source & check 2026-09-26
Source
Fact checked on
2026-09-26

Sapphire — 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
Colours covered
blue sapphire only
Only after these treatments
fissure filling with oil, fissure filling with resin
Source & check 2026-09-25
Source
Fact checked on
2026-09-25

Sapphire — care (chemicals): Fracture-filled, cavity-filled and dyed stones can be harmed even by mild acids such as lemon juice.

GIA Gem Encyclopedia (care guide)

Treatment state
treated
Only after these treatments
dyeing, filling
Source & check 2026-09-26
Source
Fact checked on
2026-09-26

Sapphire — care (chemicals): Fractures today are filled mainly with high-lead glass; such stones need more care than untreated, heated or diffused ones, as many chemicals can damage the glass, and even lemon juice can alter it.

GIA Gem Encyclopedia (care guide)

Treatment state
treated
Only after these treatments
filling
Source & check 2026-09-26
Source
Fact checked on
2026-09-26

care (wear)2 sources compared

Sapphire — care (wear): Corundum is Mohs 9 with excellent toughness and no cleavage, which makes it well suited to rings and other jewellery worn every day.

GIA Gem Encyclopedia (care guide)

Treatment state
any treatment state
Source & check 2026-09-26
Source
Fact checked on
2026-09-26

Sapphire — 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
Colours covered
blue sapphire only
Only after these treatments
fissure filling with oil, fissure filling with resin
Source & check 2026-09-25
Source
Fact checked on
2026-09-25

care (re-cutting)2 sources compared

Sapphire — care (re-cutting): Stones with superficial colour and surface layers are not suitable for re-cutting or re-polishing.

CIBJO Gemstone Book 2022

CIBJO Gemstone Book §6.2:special-care code m

Treatment state
treated
Colours covered
blue sapphire only
Only after these treatments
diffusion treatment
Source & check 2026-09-25
Source
Fact checked on
2026-09-25

Sapphire — care (re-cutting): Stones with superficial colour and surface layers are not suitable for re-cutting or re-polishing.

CIBJO Gemstone Book 2022

CIBJO Gemstone Book §6.2:special-care code m

Treatment state
treated
Only after these treatments
diffusion treatment
Applies only to
other colours, sold under a colour prefix
Source & check 2026-09-26
Source
Fact checked on
2026-09-26

Sapphire — care (re-cutting): Lattice-diffused colour penetrates to varying depths; where the coloured layer is shallow, surface damage or recutting can remove the colour.

GIA Gem Encyclopedia (care guide)

Treatment state
treated
Only after these treatments
diffusion treatment
Source & check 2026-09-26
Source
Fact checked on
2026-09-26

Sapphire — care (re-cutting): Stones with superficial colour and surface layers are not suitable for re-cutting or re-polishing.

CIBJO Gemstone Book 2022

CIBJO Gemstone Book §6.2:special-care code m

Treatment state
treated
Only after these treatments
diffusion treatment, irradiation
Applies only to
orange and pink-orange sapphire
Source & check 2026-09-26
Source
Fact checked on
2026-09-26

Sapphire — care (special care): Heated to create, deepen or lighten colour, or to improve uniformity: normal care; avoid repolishing or recutting when the effect is near the surface.

AGTA Gemstone Information Manual, 17th ed.

Treatment state
treated
Only after these treatments
heating
Source & check 2026-09-26
Source
Fact checked on
2026-09-26

Sapphire — care (special care): lattice-diffused for artificial colour or asterism: normal care, or special care (SC) when the effect is near the surface.

AGTA Gemstone Information Manual, 17th ed.

Treatment state
treated
Only after these treatments
diffusion treatment
Source & check 2026-09-26
Source
Fact checked on
2026-09-26

Sapphire — care (special care): irradiated to a temporary intense yellow or orange: special care (SC), with extra caution; fades quickly in light or heat.

AGTA Gemstone Information Manual, 17th ed.

Treatment state
treated
Only after these treatments
irradiation
Source & check 2026-09-26
Source
Fact checked on
2026-09-26

Sapphire — care (setting): prong, bezel, flush, channel and pavé: relatively safe; note: stones with pronounced twinning, fractures or many inclusions need extra care.

Gems & Gemology 1987 (Martin)

Treatment state
untreated
Source & check 2026-09-26
Source
Fact checked on
2026-09-26

Sapphire — care (repair): pickle pot and polishing: relatively safe; jeweller's torch and thermal shock: use caution; note: avoid extreme heat, which may alter colour; borax-bearing soldering flux or pickle can etch the surface.

Gems & Gemology 1987 (Martin)

Treatment state
untreated
Source & check 2026-09-26
Source
Fact checked on
2026-09-26

Sapphire — care (repair): oiled or dyed stones: avoid heat and take care in polishing.

Gems & Gemology 1987 (Martin)

Treatment state
treated
Only after these treatments
dyeing, fissure filling with oil
Source & check 2026-09-26
Source
Fact checked on
2026-09-26

Sapphire — care (display): heat in the display case, sunlight and artificial light: relatively safe.

Gems & Gemology 1987 (Martin)

Treatment state
untreated
Source & check 2026-09-26
Source
Fact checked on
2026-09-26

Sapphire — care (display): irradiated stones: avoid heat and light.

Gems & Gemology 1987 (Martin)

Treatment state
treated
Only after these treatments
irradiation
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.

Common care questions and matching entries

CleaningCleaning Sapphire: GIA states that ultrasonic and steam cleaning are usually safe for untreated Sapphire, and likewise for heat-treated or lattice-diffused stones; Martin's Gemstone Durability states that for untreated stones ultrasonic and steam cleaning call for caution; CIBJO states that only blue Sapphire treated by fracture filling with oil or resin must not be cleaned ultrasonically. Chemicals: GIA states that untreated stones are stable in normal wear, but that boric acid powder can etch the surface even of untreated stones; CIBJO states that only blue Sapphire treated by fracture filling with oil or resin should be kept away from all solvents, chemicals and high temperatures. Heat and light: AGTA states that irradiated stones in which irradiation has produced a temporary intense yellow or orange need extra special care, as the colour fades quickly on exposure to light or heat. Wear: GIA states that corundum, at Mohs 9 and with excellent toughness, is suitable for rings and other everyday wear; CIBJO states that only blue Sapphire treated by fracture filling with oil or resin breaks easily and should be worn with care.

This table scrolls sideways on narrow screens.

QuestionMatching entries
Can it go in an ultrasonic or steam cleaner?ultrasonic and steamer: use caution; note: polishing compound can get into inclusions or fractures that reach the surface; Ultrasonic and steam cleaners are usually safe, and the same holds for heat-treated and lattice-diffused stones; Cleaning with warm soapy water is safe at any time; blue sapphire only: care (cleaning); Fracture-filled, cavity-filled or dyed material should be cleaned only with a damp cloth; oiled or dyed stones: avoid solvents
Heat and thermal shockpickle pot and polishing: relatively safe; jeweller's torch and thermal shock: use caution; note: avoid extreme heat, which may alter colour; borax-bearing soldering flux or pickle can etch the surface; oiled or dyed stones: avoid heat and take care in polishing
Light and displayother colours, sold under a colour prefix: care (light); heat in the display case, sunlight and artificial light: relatively safe; irradiated stones: avoid heat and light
Contact with acids, alkalis and household chemicalsblue sapphire only: Glass, plastic or hardened-resin fillers in cavities or fractures can be scratched more readily than the stone around them, or be more easily damaged by heat or some acids (e.g. hydrofluoric); keep it away from all chemicals, heat and abrasives; stable in normal wear and not easily harmed by heat, light or common chemicals, though boric acid powder etches the surface even of untreated stones; blue sapphire only: Treatments with dye, oil, resin, wax or plastic are not permanent; keep it away from all solvents (including dish-washing liquids), chemicals and heat; Fracture-filled, cavity-filled and dyed stones can be harmed even by mild acids such as lemon juice; Fractures today are filled mainly with high-lead glass; such stones need more care than untreated, heated or diffused ones, as many chemicals can damage the glass, and even lemon juice can alter it
Wearing limits (knocks, settings)Corundum is Mohs 9 with excellent toughness and no cleavage, which makes it well suited to rings and other jewellery worn every day; blue sapphire only: cleaves or fractures easily or is brittle (e.g. rubbed facet edges); wear with care; prong, bezel, flush, channel and pavé: relatively safe; note: stones with pronounced twinning, fractures or many inclusions need extra 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.

untreated

any treatment state

treated (Only after these treatments: fissure filling with oil, fissure filling with resin)

treated (Only after these treatments: dyeing, filling)

treated (Only after these treatments: dyeing, fissure filling with oil)

treated (Only after these treatments: irradiation)

treated (Only after these treatments: filling, flux-assisted healing)

treated (Only after these treatments: filling)

treated (Only after these treatments: diffusion treatment)

treated (Only after these treatments: diffusion treatment, irradiation)

treated (Only after these treatments: heating)

Durability and wearing

Toughness

Excellent toughness

Sources GIA Gem Encyclopedia (care guide)

Treatments and identification leads

Registered treatmentsThe treatments recorded for Sapphire are flux healing, diffusion, heat treatment, filling, irradiation and dyeing. Stability and frequencyFlux healing has the status treated, stability stable and prevalence rare; diffusion, heat treatment and filling all have the status treated; irradiation has the status irradiated or dyed; dyeing has the status colour-treated. Values not givenThe stability and prevalence of the other treatments are “—”, meaning the cited source gives no value, not “none”. Identification cluesIdentification leads: diffusion shows colour concentration and a network pattern, distinguished by diffused element; heat treatment shows traces of local melting and stress cracks around inclusions; filling shows lustre differences, flash effects and gas bubbles; irradiation can give colourless, light yellow or some light blue sapphires a deep yellow or orange-yellow colour that is not stable; dyeing shows uneven colour, which comes off when wiped with solvents.

This table scrolls sideways on narrow screens.

TreatmentMarket frequency (CIBJO)Stability (CIBJO)GB/T 16552 categoryJJA/AGL listingIdentification leads
flux-assisted healingColours covered: blue sapphire onlyStatus: treatedrarelystable———
diffusion treatmentStatus: treated——Treatmentdiffusion heat treatment (any colour)See identification leads
heatingStatus: treated——Optimizationheating (any colour); heating, with residues in fissures (any colour); heating, with cavities filled by a transparent substance (any colour)See identification leads
fillingStatus: treated——Graded — see §5.4.1, Table 1—See identification leads
irradiationStatus: irradiated or dyed——Treatment—See identification leads
dyeingStatus: colour treated——Treatment—See identification leads
colouring (JJA category 7, includes dyeing)———colouring (JJA category 7, includes dyeing) (any colour)—
lead-glass impregnation———lead-glass impregnation (other colours + lead glass)—

Where each treatment acts (schematics): Heated / Heat-treated · Diffusion-treated · Filled / Fracture-filled · Irradiated · Dyed

“—” means the cited source gives no value for that item, not “none”. Source: CIBJO Gemstone Book 2022 · GB/T 16553—2017; GB/T 16552—2017 Table B.1; JJA/AGL 2025

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 Sapphire is set out under report wording on the Corundum entry.

A general LMHC wording rule also covers Sapphire (Information Sheet #16): see the LMHC rule “Colour stability testing”.

VerifyNames, standards, technical facts, clauses and sources

Names

Besides Sapphire, the name register records "Fancy sapphire", for which no restriction on use as a name is recorded; 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 GB/T 16552—2017 formal name for Sapphire is given in Table A.1, the suggested listing name is Sapphire, and Fancy sapphire is a trade name/synonym. Institution usageOn authority wording, GIA, FTC and CIBJO list Sapphire, and Gem-A is unchecked; bodies without a recorded wording show the entry's own English name, which does not represent their position. GIA's wording carries a qualifier stripped from the headline name: corundum variety, all colours other than red. Names in four languagesNames are given in Simplified Chinese, Traditional Chinese, English (Sapphire) and Japanese, the Japanese name being the GSJ (Japan) formal name. National standard namesNational and regional formal names: Germany (RAL) Saphir, the European Union Sapphire, India (BIS) Sapphire/Neelam (नीलम), Thailand (GIT) Sapphire/Phailin, noting that Chanthaburi heat treatment is of global importance, and France (DGCCRF) Saphir. Trade and mineralogical namesIn the name register, Fancy sapphire is a market name; Burmese sapphire is a market name but, under GB/T 16552—2017, not a usable name, because origin should not form part of the name; it is a counter-example, not a trade name.

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.

NameTypeMatchingUse as a nameBasis
no restriction recorded (1)
Fancy sapphireEnglishmarket namematched automaticallyno restriction recordededitorial ruling (no clause cited)
not to be used as a name (1)
缅甸蓝宝石Simplified Chinesemarket namematched automaticallynot to be used as a nameGB/T 16552—2017 5.1.2.1 b); Note: GB/T 16552—2017 §5.1.2.1 b) uses it as the example of a rule: origin must not form part of the name (a counter-example, not a trade name).

How each authority words this name: see Names › Authority wording.

Authority wording

GIA, FTC, CIBJO, Gem-A
Sapphire (on record for GIA, FTC, CIBJO (16 CFR Part 23 §23.25; CIBJO Gemmological Laboratories Book 2024); Gem-A unchecked — bodies without a recorded wording show the entry's own English name)
GSJ (Japan) formal name
サファイア／青玉
Chinese formal name
蓝宝石 (GB/T 16552—2017 Table A.1)
Mineralogical name
Gem corundum other than ruby; colour must be specified where relevant
Trade names and synonyms
Fancy sapphire (market name)

Four-language names

简体中文
蓝宝石
繁體中文
藍寶石
English
Sapphire
日本語
サファイア／青玉

National and regional formal names

Germany (RAL)
Saphir
European Union
Sapphire
India (BIS)
Sapphire / Neelam (नीलम)
Thailand (GIT)
Sapphire / Phailin; Chanthaburi heat-treatment is globally significant
France (DGCCRF)
Saphir

Qualifiers stripped from the headline name

  • GIA: (corundum variety; all non-red colors)

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; common industry optimization (verify with certificate)

Treatments listed by standards

GB/T Table B.1The sapphire row of GB/T 16552—2017 Annex B Table B.1 lists for Sapphire: heat treatment, classed as an enhancement; dyeing, classed as a treatment; filling, categorised by grade; diffusion treatment, classed as a treatment; irradiation, classed as a treatment. JJA/AGL designationsIn the Japanese JJA/AGL 2025 table, for Sapphire, heating, and heating with residues left in fractures, are recorded as heat treatment; heating with cavities filled with a transparent substance is recorded as heat treatment and filling; diffusion heating is recorded as diffusion treatment; colouring, including dyeing, is recorded as dyeing; where no treatment is listed, it notes that no evidence of heating was seen, with reference to heat treatment. Sapphire + Lead Glass is listed separately, with lead-glass impregnation recorded as filling. See alsoThe notes to Table B.1, the definitions of the filling grades and how to read the JJA/AGL table are all on the treatments page.

GB/T 16552-2017, Annex B, Table B.1

Table B.1, row “Sapphire” (p.14):

This table scrolls sideways on narrow screens.

MethodEffectCategory
HeatingImproves appearanceOptimization
DyeingImproves or changes colourTreatment
FillingImproves or changes durability and appearanceGraded — see §5.4.1, Table 1
DiffusionImproves colour or produces asterismTreatment
IrradiationChanges colourTreatment

What Table B.1 is, and how the “see 5.4.1” grades are defined: see the GB/T 16552: optimization vs treatment page.

JJA/AGL (Japan) table of principal gem names, 2025

This table scrolls sideways on narrow screens.

Gem nameSpeciesColourListed in the tableNotes
[colour] SapphireCorundumany colourno treatment listed (noted: no indication of heating) (see Heated / Heat-treated); heating (Heated / Heat-treated); heating, with residues in fissures (Heated / Heat-treated); heating, with cavities filled by a transparent substance (Heated / Heat-treated, Filled / Fracture-filled); diffusion heat treatment (Diffusion-treated); colouring (JJA category 7, includes dyeing) (Dyed)adding the colour variety to the blank prefix is optional
[colour] Sapphire + Lead GlassCorundum+lead glassother colours + lead glassthe source lists no untreated tier; lead-glass impregnation (Filled / Fracture-filled)named “(colour) sapphire + lead glass”; colour variety optional

JJA/AGL definitions and nomenclature (2025 revision), table of principal gem names, p.12, 13

How to read the JJA/AGL table: see the Gem treatments page.

What it is and how it's identified

Registered material facts for Sapphire: composition is Al2O3 and may contain elements such as Fe, Ti, Cr, V and Mn, the phase being corundum; the structure is crystalline, trigonal, with a habit of hexagonal prisms or barrels, occasionally tabular or bladed. Sapphire has a Mohs hardness of 9 and no cleavage, although stones with well-developed twinning may show parting in three directions. Density is 3.95–4.1 g/cm³, derived from the cited clause value of 4.00 with a tolerance of +0.10/−0.05. Optical character is anisotropic, uniaxial negative; refractive index is 1.757–1.779, derived from the cited clause value of 1.762–1.770 with a tolerance of +0.009/−0.005; birefringence is 0.008–0.01. Untreated Sapphire shows strong pleochroism that varies with body colour, and untreated Sapphire has a vitreous to subadamantine lustre.

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

Sapphire — composition (chemistry): Al2O3, elements such as Fe,Ti,Cr,V and Mn 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): §5.1.3 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Sapphire — composition (phase): corundum

CIBJO Gemmological Laboratories Book 2024

Source & check 2026-09-22
Source
Fact checked on
2026-09-22

Structure

Sapphire — 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): §5.1.3 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Sapphire — structure (crystal system): trigonal

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): §5.1.3 (locator checked 2026-09-21)
Fact checked on
2026-09-21

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
Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.1.3 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Durability

Sapphire — Mohs hardness: 9

GB/T 16553—2017

123456789109References (diamond = value, bar = range; below)

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))

Mohs hardnessSource: GB/T 16553—2017
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): §5.1.3 (locator checked 2026-09-21)
Fact checked on
2026-09-21

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
Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.1.3 (locator checked 2026-09-21)
Fact checked on
2026-09-21

For Sapphire, the stability of flux-assisted healing is “stable”.

CIBJO Gemstone Book 2022

Treatment state
treated
Treatment
flux-assisted healing
Colours covered
blue sapphire only
Qualification

This says how well the treatment holds up, not how durable Sapphire itself is.

General note
no durability verdict here
Source & check 2026-09-25
Source
Fact checked on
2026-09-25

Physical properties

Sapphire — density: 3.95–4.1 g/cm³

GB/T 16553—2017

0.51.52.53.54.55.56.57.53.95–4.1
Specific gravitySource: GB/T 16553—2017
Does this standard apply
applies to this entry
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 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.1.3 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Optical

Optical effects on record: asterismrepresentative example: cause in Star Sapphire (schematic)colour change

Sapphire — optic character: uniaxial, optically negative (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): §5.1.3 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Sapphire — refractive index: 1.757–1.779

GB/T 16553—2017

1.31.72.12.52.93.31.757–1.779
Refractive indexSource: GB/T 16553—2017
Does this standard apply
applies to this entry
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 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.1.3 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Sapphire — birefringence: 0.008–0.01

GB/T 16553—2017

00.050.10.150.20.250.30.008–0.01
BirefringenceSource: 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): §5.1.3 (locator checked 2026-09-21)
Fact checked on
2026-09-21

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
Source & check 2026-09-22
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.1.3 (locator checked 2026-09-22)
Fact checked on
2026-09-22

Sapphire — fluorescence (overall): blue: long wave none to strong, orange-red; short wave none to weak, orange-red; pink: long wave strong, orange-red; short wave weak, orange-red; orange: generally none; long wave may show strong, orange-red; yellow: long wave none to moderate, orange-red, orange-yellow; short wave weak, red to orange-yellow; violet and colour-change: long wave none to strong, red; short wave none to weak, red; colourless: none to moderate, red to orange; black, green: none.

GB/T 16553—2017

UV fluorescenceorange-rednone–strong, blueorange-rednone–weakorange-redstrong, pinkorange-redweakmay show: orange-redstrong, orangeorange-redorange-yellownone–moderate, yellowredorange-yellowweakrednone–strong, violet and colour-changerednone–weakredorangenone–moderate, colourlessDots 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): §5.1.3 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Sapphire — spectrum (UV-visible): blue, green, yellow: 450 nm absorption band; or 450 nm absorption peak; 460 nm absorption peak; 470 nm absorption peak; pink, violet and colour-change sapphire: shows the absorption bands of ruby and of blue sapphire.

GB/T 16553—2017

400450500550600650700 nmblue, green, yellow450460470
Absorption spectrum (schematic)Line = absorption peak; hatching = absorption band; heavier or darker = higher recorded strength grade (not a measured intensity); Schematic: positions and strength grades as given by the cited source, not a measured curveSource: 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): §5.1.3 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Sapphire — spectrum (infrared): Corundum's Al-O vibration is the source of its diagnostic mid-IR bands

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): §5.1.3 (locator checked 2026-09-22)
Fact checked on
2026-09-22

Sapphire — optical effect (asterism): seen; commonly a six-rayed star

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): §5.1.3 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Sapphire — 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): §5.1.3 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Sapphire — magnification: gas-liquid inclusions, fingerprint-like inclusions, mineral inclusions, color band, growth striations, twin striations, negative crystals, "silk" inclusions, needle inclusions, mist-like inclusion.

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): §5.1.3 (locator checked 2026-09-21)
Fact checked on
2026-09-21

body colour2 sources compared

Sapphire — body colour: Violetish blue, blue to greenish blue.

CIBJO Gemmological Laboratories Book 2024

Treatment state
untreated
Qualification

In chapter 7 of the CIBJO Gemmological Laboratories Book, the colour descriptions of Tanzanite, Lazulite, Paraíba Tourmaline and other entries also name blue or a bluish colour.

General note
colour alone is not identity
Source & check 2026-09-22
Source
Fact checked on
2026-09-22

Sapphire — body colour: colorless, grey, black, green, blue-green, blue, purple, pink, orange, yellow and others.

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 Sapphire overlap with this entry: blue, green, yellow, orange, pink and colourless.

General note
colour alone is not identity
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

How the sources relate

CIBJO Gemmological Laboratories Book 2024 and GB/T 16553—2017

different scope

The two entries cover different ranges.

The entry in the CIBJO Gemmological Laboratories Book refers to blue corundum only (violetish blue, blue to greenish blue) and notes that other colours usually take a colour prefix; the GB/T 16553—2017 sapphire entry lists blue, blue-green, green, yellow, orange, pink, purple, black, grey, colourless and other colours. They agree on blue.

CIBJO definitions
asterism, colour change

Quality factors

Sapphire — 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): §5.1.3 (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.

1.741.761.781.83.83.944.14.2Refractive indexSpecific gravity12345Sapphire

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)1.41.51.61.71.81.922.12.22.32.41234567Refractive indexSpecific gravity12345Sapphire

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

Refractive index × specific gravity (all registered materials)Each dot is one material's registered refractive index and specific gravity (range midpoints, not measurements); gold = this material, dark = the nearest few (picked on this site by distance in RI ÷ 0.02 and SG ÷ 0.1, leaving out near-identical varieties of the same species)Source: each material's registered refractive index and specific gravity facts (GB/T 16553 and others; sources on each entry)

Testing and market

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: §6.1.69.

How far testing can go

Sapphire that has undergone diffusion treatment can be identified by the following features: Magnification shows color concentrated in fissures and hollows.

By diffused element: diffusion-treated star sapphire has thin, straight star rays and a surface layer flecked with white points; beryllium-diffused sapphire shows surface microcrystallization and recrystallization of its zircon inclusions; cobalt-diffused sapphire shows light blue spots on the surface.

Viewed under magnification in immersion or in scattered light, the color concentrates along edges, the girdle or fissures in a net-like pattern, though on beryllium-diffused sapphire this is mostly indistinct. As to fluorescence, some diffusion-treated blue sapphires may glow blue-white or blue-green under short-wave ultraviolet light.

As to absorption, some diffusion-treated blue sapphires lack the 450 nm absorption band, while cobalt-diffused sapphire shows the characteristic absorption bands of cobalt. Compositional analysis (LA-ICP-MS and the like) can detect an abnormal content of the diffused element — beryllium, for instance — in the surface layer, the concentration falling from the surface inwards.

GB/T 16553—2017

Treatment state
treated
Does this standard apply
can be followed as a reference only
Treatment
diffusion treatment
Source & check 2026-09-22
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.1.3 (diffusion treatment) (locator checked 2026-09-22)
Fact checked on
2026-09-22

Sapphire that has undergone heating can be identified by the following features: Under magnification the surface shows traces of local melting, disc-like and ring-like stress fissures appear around solid inclusions, negative crystals look corroded or rounded at the rim, silk and needle inclusions break up into discontinuous silk or fine dots, and some heated sapphire shows weak blue-green or green-white fluorescence under short-wave UV.

GB/T 16553—2017

Treatment state
treated
Does this standard apply
can be followed as a reference only
Treatment
heating
Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.1.3 (heating) (locator checked 2026-09-21)
Fact checked on
2026-09-21

Sapphire that has undergone filling can be identified by the following features: Under magnification the surface luster of the filled part differs from that of the host stone, and a flash effect and gas bubbles can be seen in the filled area; infrared and Raman spectra show characteristic peaks of the filler; luminescence imaging (such as a UV fluorescence viewer) shows how the filler is distributed; compositional analysis (such as XRF) detects abnormal amounts of foreign elements such as lead and bismuth.

GB/T 16553—2017

Treatment state
treated
Does this standard apply
can be followed as a reference only
Treatment
filling
Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.1.3 (filling) (locator checked 2026-09-21)
Fact checked on
2026-09-21

Sapphire that has undergone irradiation can be identified by the following features: Irradiation can turn colourless, light yellow and some light blue sapphire deep yellow or orange-yellow; the colour is not stable and the treatment is not easy to detect.

GB/T 16553—2017

Treatment state
irradiated or dyed
Does this standard apply
can be followed as a reference only
Treatment
irradiation
Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.1.3 (irradiation) (locator checked 2026-09-21)
Fact checked on
2026-09-21

Sapphire that has undergone dyeing can be identified by the following features: Under magnification the colour is unevenly distributed and mostly concentrated between fissures or in surface hollows; the dye can show an unusual fluorescence in long- and short-wave ultraviolet; there is no obvious pleochroism; the UV-visible spectrum looks abnormal; wiping with acetone or absolute ethanol can lift the colour.

GB/T 16553—2017

Treatment state
colour treated
Does this standard apply
can be followed as a reference only
Treatment
dyeing
Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.1.3 (dyeing) (locator checked 2026-09-21)
Fact checked on
2026-09-21

For Sapphire in trade, the reported frequency of flux-assisted healing is “rarely”.

CIBJO Gemstone Book 2022

Treatment state
treated
Treatment
flux-assisted healing
Colours covered
blue sapphire only
Source & check 2026-09-25
Source
Fact checked on
2026-09-25

Sapphire — what the CIBJO laboratory protocol says to watch for: heat treatment, diffusion, (lead, cobalt) glass filling, Synthetics.

CIBJO Gemmological Laboratories Book 2024

Treatment state
any treatment state
Source & check 2026-09-26
Source
Fact checked on
2026-09-26

Sapphire — notes on test methods in the CIBJO laboratory protocol:

CIBJO laboratory protocol, in its own order; only the notes registered on this site
Test methodWhat the protocol notes for it
Phenomena: Star, colour change;
Immersion: Synthetic, Be diffusion;
DiamondView: Glass filling;
UV-Visible(-NIR) spectroscopy: Be diffusion, if necessary for origin;
LA-ICP-MS Chemistry: Be test heated stones, if necessary for origin;
Residue check/ extent: Flux healing;
Colour call: e.g., Padparadscha

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

Sapphire has a direct definition in the CIBJO Gemmological Laboratories Book 2024 under the term Sapphire, which describes it as the violetish blue, blue to greenish blue variety of corundum. The cross-check shows it is defined directly by CIBJO and also appears in the GB/T annex.

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TermClauseDefinitionCross-check
Sapphire7.2.1.204Violetish blue, blue to greenish blue variety of corundumDefined directly by CIBJO; also present in the GB/T annex.

Evidence and sources

Authority basis and clause sources

GB/T 16552—2017
Listed Table A.1 “Sapphire” · Source
IMA Mineral List 2026-07
Listed “Corundum” · Source
CIBJO Gemmological Laboratories Book 2024
Listed §7.2.1.204 “Sapphire” · Source

Sources

Further reading

Related pages

Treatments recorded for this material

Recorded cultural contexts

Birthstone list

The U.S. Jewelers of America roster lists Sapphire for September; the U.K. National Association of Jewellers chart lists Sapphire (blue) as traditional for September; and Japan's JJA 2021 revised roster lists Sapphire for September. This records trade-association convention only; it does not establish material identity, natural origin, treatment, provenance, or effect.

Relation
Industry list inclusion

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Publisher or holderRegionFrom / periodSource and locator
Jewelers of AmericaUnited States1912 to the presentJewelers of America, “Birthstone Jewelry” (web page, consulted 2026-08-22)
Birthstone roster table, September row: Sapphire
Japan Jewellery AssociationJapanfrom 20 December 2021Tanjoseki (Japanese birthstone roster, Japan Jewellery Association page; revision of 20 December 2021)
2021 revised birthstone roster, September row: Sapphire
National Association of JewellersUnited Kingdom—National Association of Jewellers, “Zodiac Birthstones Jewellery: Star Signs, Gemstones and Their Meaning” (web page, consulted 2026-08-22)
Zodiac birthstone chart, September row: Sapphire (blue) (Traditional)

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 (Sapphire) is marked.

This table scrolls sideways on narrow screens.

PageContentStatus
Browsing familyOxide mineralsLive
Treatments recorded for this materialHeated / Heat-treated, Diffusion-treated, Dyed, Filled / Fracture-filled, IrradiatedLive
Related articlesTo be added (placeholder)Planned

Who maintains this page

The material facts in the 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.

Facts editor
June
Reviewer
Ralph
How facts are checked
Each fact is matched to the clause it cites; facts checked between 2026-09-21 and 2026-09-26
Last revised
2026-10-13
Purpose
Lets buyers and sellers check naming, disclosure and material facts clause by clause.

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