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

Ruby

The red gem variety of Corundum; heat treatment is extremely common, filling and diffusion treatments are also common, and all must be disclosed in 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 2026-10-12Who maintains this page

FAQCare and wear

Questions people ask about Ruby

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

Q1Can you tell a natural ruby from a synthetic one by eye?

Usually not: natural and synthetic ruby can look all but identical, and without diagnostic inclusions or growth features traditional gemmology often falls short.G&G Summer 1998A laboratory separates them by trace-element chemistry, reading the signature with energy-dispersive X-ray fluorescence and combining it with microscopy of growth striations and inclusions.G&G Summer 1998Synthetic ruby is common in the trade.CIBJO Gemstone Book 2022According to the parent entry Corundum, corundum can be confused by colour, sometimes even with other gems, and appearance plus a single measurement is not always enough.G&G Fall 2019 (via parent entry Corundum)Whether one particular bead is natural, treated or synthetic — only a laboratory report can settle that.What this page can answer

Q2What makes a ruby red?

Chromium: ruby is the red gem variety of corundum (Al2O3), with chromium (Cr3+) as its chromophore.G&G Winter 2019Its colour runs from purplish red and pinkish red to red and slightly orangish red.CIBJO Gemmological Laboratories Book 2024The intense pigeon's blood red and high transparency relate to the metamorphic conditions and the purity of the original rock.G&G Winter 2019

Q3How are rubies treated, and which treatments need extra care?

Rubies heated to improve colour and appearance, with no residue visible at 10x, need only normal care.AGTA Gemstone Information Manual, 17th ed.Rubies whose surface cavities and fractures were deliberately filled with glass or other foreign material need special care: avoid heat, ultrasonic cleaning and common household chemicals.AGTA Gemstone Information Manual, 17th ed.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)Rubies lattice-diffused for artificial colour or asterism need normal care, or special care when the effect lies near the surface.AGTA Gemstone Information Manual, 17th ed.Rubies dyed with coloured oil need special care and should be kept from household chemicals.AGTA Gemstone Information Manual, 17th ed.

Q4Is ruby tough enough for an everyday ring?

Yes: corundum is Mohs 9 with excellent toughness and no cleavage, which makes ruby well suited to rings and other jewellery worn every day.GIA Gem Encyclopedia (care guide)Ruby 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)For dyed or oil- or resin-filled rubies, CIBJO's care notes flag that they can cleave, fracture or be brittle, for example at rubbed facet edges, and advise wearing them with care.CIBJO Gemstone Book 2022

Q5How should you clean a ruby ring?

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)For dyed or oil- or resin-filled rubies, CIBJO advises against ultrasonic cleaning, because some stones can be damaged by it.CIBJO Gemstone Book 2022Fracture-filled, cavity-filled or dyed rubies 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)

Q6What is the difference between a ruby and a sapphire?

Only colour and its cause: ruby and sapphire share the same mineral, corundum, differing only in colour and chromophore.G&G Winter 2019 · G&G Summer 2023According to the parent entry Corundum, pure corundum is colourless, and in natural corundum Cr3+ gives pink to red while the Fe2+-Ti⁴⁺ pair gives blue.G&G Spring 2020 (via parent entry Corundum)Where the line falls depends on colour: if the red is too light, a stone may be considered a pink sapphire even when its colour is strong.GIA Ruby Quality Factors · GIA Sapphire Quality Factors

Q7How do rubies form?

Corundum is a high-temperature mineral that forms mainly when alumina-rich rocks are metamorphosed under amphibolite- to granulite-facies conditions, at about 500–800°C.G&G Winter 2019Chromium and related chromophores, from evaporites or ultramafic rocks, enter the corundum lattice and turn it red.G&G Winter 2019Marble-hosted ruby formed during retrograde metamorphism at about 620–670°C and 2.6–3.3 kbar, with evaporite layers aiding chemical exchange.G&G Winter 2019Ruby is also carried to the surface from depth as xenocrysts or megacrysts in continental alkali basalt.G&G Winter 2019Its formation relates to two main orogenies: the Pan-African (750–450 Ma) and the Himalayan (about 60 Ma to present).G&G Winter 2019 · G&G Summer 2023

Q8Does ruby fade in sunlight?

No: ruby is stable in normal wear and not easily harmed by heat, light or common chemicals.GIA Gem Encyclopedia (care guide)For display, case heat, sunlight and artificial light are all rated relatively safe.Gems & Gemology 1987 (Martin)Irradiated stones are the exception and should be kept from heat and light.Gems & Gemology 1987 (Martin)

Q9What makes a good-quality ruby?

According to GIA, colour is the most important quality factor for ruby: the finest is a pure, vibrant red to slightly purplish red, neither too dark nor too light.GIA Ruby Quality FactorsSome inclusions are expected, since inclusion-free rubies are practically non-existent; obvious inclusions, or inclusions that reduce transparency or brightness, count heavily against a ruby.GIA Ruby Quality FactorsFor star rubies, 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)

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

There is no scientific evidence that ruby 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 July birthstone: Jewelers of America and Japan's JJA list it for July, and the U.K. National Association of Jewellers lists it as traditional for July.Cultural recordsIn museum collections, ruby appears as a setting mainly in 16th–19th-century jewellery, with no ancient examples, and some records say ruby and/or garnet, so the identification is not certain.The Met 1974.356.649 · The Met 36.25.2793 +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

Ruby is the red gem variety of corundum (Al2O3), coloured by chromium (Cr3+). Corundum is a high-temperature mineral that forms mainly during amphibolite- to granulite-facies metamorphism of alumina-rich rocks (~500-800°C), so ruby occurs as both metamorphic and magmatic varieties. Key metamorphic types include marble-hosted ruby in Central/Southeast Asia (formed during retrograde metamorphism at ~620-670°C and 2.6-3.3 kbar, with Al and chromophores derived from impure carbonate protoliths aided by evaporite layers), and amphibolite-type ruby hosted in mafic-ultramafic rocks (M-UMR, amphibolite-granulite facies, ~750-800°C). Ruby also occurs as xenocrysts in alkali basalts. Key point: ruby and sapphire share the same mineral, corundum, differing only in colour and chromophore; whereas jade (jadeite) is a pyroxene formed under high-pressure, low-temperature subduction conditions. The two mechanisms have nothing in common and their deposit models must not be generalised across each other.

Scope: Covers red corundum (ruby); P-T and host-rock conditions for different deposit types such as marble-hosted and amphibolite-hosted must be cited separately and must not be generalised.

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

Where it forms

Metamorphic marble type: metasomatised impure carbonate with evaporite layers, amphibolite-granulite facies, ~620-670°C / 2.6-3.3 kbar.

Sources G&G Winter 2019

Amphibolite type in mafic-ultramafic rocks (M-UMR): ~750-800°C, high-pressure amphibolite- to granulite-facies.

Sources G&G Winter 2019

Continental alkali basalt: ruby carried to the surface as xenocrysts/megacrysts from depth.

Sources G&G Winter 2019

How it forms, step by step

  1. Alumina-rich protoliths (limestone, meta-mafic rocks) undergo rising pressure and temperature during orogeny.

    Sources G&G Winter 2019

  2. Under amphibolite- to granulite-facies conditions Al2O3 components crystallise/recrystallise as corundum.

    Sources G&G Winter 2019

  3. Chromium and related chromophores (from evaporites or ultramafic rocks) enter the corundum lattice, turning it red.

    Sources G&G Winter 2019

  4. After uplift and weathering, primary ore or eluvial/alluvial placers form.

    Sources G&G Winter 2019

Link to appearance

Chromium (Cr3+) in the corundum lattice causes red colour; the intense 'pigeon's blood' red and high transparency relate to metamorphic conditions and protolith purity.

Sources G&G Winter 2019

Timescale

Formation relates to two main orogenies: the Pan-African (750-450 Ma) and the Himalayan (~60 Ma to present).

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

Related base materials

  • Corundum: Mineral parent: ruby is the red gem variety of corundum (colouring element Cr)
  • Sapphire: A gem variety of the same species (corundum) in a different colour; the names are mutually exclusive

Supporting findings

Marble-hosted ruby formed during retrograde metamorphism at ~620-670°C and 2.6-3.3 kbar, with evaporite layers aiding chemical exchange.

Evidence grade A

Scope: This P-T range is specific to certain marble-type localities and is not applicable to other types.

Sources G&G Winter 2019

Corundum is a high-temperature mineral that forms mainly under amphibolite- to granulite-facies metamorphism of alumina-rich rocks (~500-800°C).

Evidence grade A

Scope: General conditions for metamorphic corundum; magmatic corundum has other mechanisms.

Sources G&G Winter 2019

Metamorphic corundum formation is tied to two major events: the Pan-African orogeny (750-450 Ma) and the Himalayan orogeny (60 Ma to present).

Evidence grade A

Scope: Covers most metamorphic corundum localities; individual deposits may have older or younger ages.

Sources G&G Summer 2023 · 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

Europe

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.

Human use and museum objects

The collection evidence shows ruby used as a setting mainly in 16th-19th-century jewellery (e.g. Met 1974.356.649, 36.25.2793, 15.95.39, 1991.32.2; Cleveland 1944.70) with no ancient examples; the evidence pertains to the corundum parent material, and some records say "ruby and/or garnet", so the identification is not certain.

Evidence grade A

Scope: Applies to collection jewellery recorded as ruby (the red corundum variety) from Europe, India and Southeast Asia; the evidence pertains to the corundum parent material, and some material records are uncertain.

Sources The Met 1974.356.649 · The Met 36.25.2793 · The Met 15.95.39 +3

Objects recorded as ruby in these collections are almost all jewellery, and relatively late — no ancient examples appear. Among the earlier are a gold-and-enamel gimmel ring of the second half of the 16th century (Met 1974.356.649, with rubies) and a 16th-17th-century Turkish archer's thumb ring (Met 36.25.2793; jade, gold, emeralds, ruby). British 18th-century rings include Met 2000.536 (ca. 1765) and 2000.535 (ca. 1740-60). Indian Mughal and regional gold is a major group: a 19th-century gold bracelet (Met 15.95.39), a South Indian jasmine-bud necklace (Met 1991.32.2, Tamil Nadu and Kerala), and a 19th-century Cambodian ring (Cleveland 1944.70). Ruby is the red gem variety of corundum (coloured by Cr); this record is not an independent material and the evidence pertains to the corundum parent material. Ambiguous material fields such as "ruby and/or garnet" and design watercolours (e.g. 53.626.2(5)) are not counted.

Sources The Met 1974.356.649 · The Met 36.25.2793 · The Met 2000.535 +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

150015501600165017001750180018501900Met 36.25.279316th–17th centuryMet 1974.356.649second half 16th centuryMet 2000.535ca. 1740–60Met 2000.536ca. 1765CMA 1944.701800sMet 15.95.3919th centuryMet 1991.32.219th 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 1974.356.649Gimmel ring (Twin ring) · second half 16th centuryGold, enamel, rubies, emerald
  • The Met 36.25.2793Archer's Thumb Ring · 16th–17th century · Turkish · TurkeyJade, gold, emeralds, ruby
  • The Met 2000.535Ring · ca. 1740–60 · British · EnglandGold, diamonds, rubies, and emerald
  • The Met 2000.536Ring · ca. 1765 · British · EnglandGold, rubies, crystal, and hair
  • The Met 15.95.39Bracelet (Kada), One of a Pair · 19th century · IndiaGold and rubies
  • The Met 1991.32.2Jasmine Bud Necklace (Malligai Arumbu Malai) · 19th century · India (Tamil Nadu and Kerala)Gold with rubies strung on black thread
  • Cleveland Museum of Art 1944.70Ring · 1800s · Cambodiagold with rubies

Cultural records for this material: Birthstone list.

How it is identified

Natural and synthetic ruby can appear all but identical, and where diagnostic inclusions or growth features are absent, traditional gemology often falls short. A laboratory can separate them by trace-element chemistry: energy-dispersive X-ray fluorescence is used to read the trace-element signature, combined with microscopy of growth striations and inclusions; individual stones may prove exceptional, so the conclusion must be issued by an accredited laboratory and the method needs dedicated equipment.

Evidence grade A

Scope: Natural/synthetic ruby determination must be issued by an accredited laboratory with specialist instruments; individual stones may depart from general trends.

Sources G&G Summer 1998

Ruby is often priced on locality, with goods traded under names such as Burma, Mozambique, Madagascar, Thailand or Cambodia. 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

Other research findings

Ruby is the red gem variety of corundum (Al2O3), with chromium (Cr3+) as its chromophore.

Evidence grade A

Scope: Strictly red corundum; the classification of pink corundum is debated in the literature.

Sources G&G Winter 2019

Ruby (corundum) and jade (jadeite) belong to different minerals and formation mechanisms; their deposit models must not be generalised across each other.

Evidence grade A

Scope: A material-and-genesis boundary statement preventing cross-material misuse.

Sources G&G Summer 2023

Per the Winter 2025 GIA Gems & Gemology article In the Spotlight, the 'Queen of Passion' necklace centres on an unheated 5 ct Burmese ruby that the article calls an extraordinary size for its quality; the separate 1988 article notes a 167 ct Edwardes ruby among the Crown Jewels of England. Neither is described by the sources as the world's largest ruby; these accounts come from 2025 and 1988 literature and may since have been overtaken.

Evidence grade A

Scope: Records the sources' descriptions of specific objects; neither source calls these the world's largest ruby. Records change over time; the accounts come from 2025 and 1988 literature.

Sources G&G Winter 2025 · G&G Spring 1988

Colour is the most important quality factor for ruby. The finest ruby is a pure, vibrant red to slightly purplish red, neither too dark nor too light.

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 Ruby Quality Factors

Rubies are expected to contain some inclusions, since inclusion-free rubies are practically non-existent; obvious inclusions, or inclusions that reduce transparency or brightness, count heavily against a ruby.

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 Ruby Quality Factors

Ruby and pink sapphire are both corundum; red corundum is called ruby and corundum of other colours is sapphire. Where the line falls depends on colour: if the red is too light, the stone may be considered a pink sapphire even when its colour is strong.

Evidence grade B

Scope: Describes how one educational source draws the line; laboratories and markets differ on exactly where it lies, and the call on any single stone rests with a gemmological laboratory.

Sources GIA Ruby Quality Factors · GIA Sapphire Quality Factors

Limits of this research

  • Research status: Formation, occurrence or other material-specific findings found in authoritative sources
  • Classification of pink corundum/'pink sapphire' is debated; this record treats its genesis as ruby-related.
  • P-T and host-rock conditions across marble, amphibolite and basalt types are not interchangeable.
  • Heat treatment and other enhancements complicate provenance judgement and 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
Ruby

GB/T 16552—2017 Table A.1 “Ruby” · 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, Filled / Fracture-filled, Diffusion-treated, Dyed

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

Ruby is often subjected to heating, filling 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); filling is graded by the material used, and must be stated in the name wherever it counts as a treatment (§5.4.1, Table 1); 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 红宝石 (Ruby)

What this means for you

Before buying, check the recommended listing name "Ruby" 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

Ruby — care (cleaning): Some stones are susceptible to damage from ultrasonic cleaning. Do not expose them to ultrasonic cleaning.

CIBJO Gemstone Book 2022

CIBJO Gemstone Book §6.2:special-care code j

Treatment state
treated
Only after these treatments
dyeing, fissure filling with oil, fissure filling with resin
Source & check 2026-09-25
Source
Fact checked on
2026-09-25

Ruby — 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

Ruby — 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

Ruby — 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

Ruby — 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

Ruby — 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

care (chemicals)2 sources compared

Ruby — 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

Ruby — care (chemicals): Treatments with dye, oil, resin, wax or plastic are not permanent; keep it away from all solvents (including dish-washing liquids), chemicals and heat.

CIBJO Gemstone Book 2022

CIBJO Gemstone Book §6.2:special-care code k

Treatment state
treated
Only after these treatments
dyeing, fissure filling with oil, fissure filling with resin
Source & check 2026-09-25
Source
Fact checked on
2026-09-25

Ruby — care (chemicals): particularly susceptible to attack by acids, so keep it away from acids; 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 h, special-care code l

Treatment state
treated
Only after these treatments
filling
Source & check 2026-09-25
Source
Fact checked on
2026-09-25

Ruby — 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

Ruby — 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

care (wear)2 sources compared

Ruby — care (wear): cleaves or fractures easily or is brittle (e.g. rubbed facet edges); wear with care.

CIBJO Gemstone Book 2022

CIBJO Gemstone Book §6.2:special-care code b

Treatment state
treated
Only after these treatments
dyeing, fissure filling with oil, fissure filling with resin
Source & check 2026-09-25
Source
Fact checked on
2026-09-25

Ruby — 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

care (re-cutting)2 sources compared

Ruby — 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
Source & check 2026-09-25
Source
Fact checked on
2026-09-25

Ruby — 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

Ruby — care (special care): surface cavities and fractures deliberately filled with glass or other foreign material (visible at 10x): special care (SC); avoid heat, ultrasonic and common household chemicals.

AGTA Gemstone Information Manual, 17th ed.

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

Ruby — care (special care): dyed with coloured oil: special care (SC); avoid household chemicals.

AGTA Gemstone Information Manual, 17th ed.

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

Ruby — care (special care): heated to improve colour and appearance (no residue visible at 10x): normal care.

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

Ruby — care (special care): lattice-diffused for artificial colour or asterism: normal care, or special care (SC) when the effect lies 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

Ruby — care (special care): irradiated to change colour: normal care; if neutron-irradiated, follow the irradiation-code safety rules.

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

Ruby — 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

Ruby — 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

Ruby — 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

Ruby — 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

Ruby — 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

Each question links to the matching entries on this page; whether they answer it fully, go by the entry wording.

This table scrolls sideways on narrow screens.

QuestionMatching entries
Can it go in an ultrasonic or steam cleaner?care (cleaning); Cleaning with warm soapy water is safe at any time; oiled or dyed stones: avoid solvents; ultrasonic and steamer: use caution; note: polishing compound can get into inclusions or fractures that reach the surface; Fracture-filled, cavity-filled or dyed material should be cleaned only with a damp cloth; Ultrasonic and steam cleaners are usually safe, and the same holds for heat-treated and lattice-diffused stones
Heat and thermal shockoiled or dyed stones: avoid heat and take care in polishing; 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
Light and displayheat in the display case, sunlight and artificial light: relatively safe; irradiated stones: avoid heat and light
Contact with acids, alkalis and household chemicalsFractures 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; Treatments with dye, oil, resin, wax or plastic are not permanent; keep it away from all solvents (including dish-washing liquids), chemicals and heat; particularly susceptible to attack by acids, so keep it away from acids; 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; Fracture-filled, cavity-filled and dyed stones can be harmed even by mild acids such as lemon juice; 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
Wearing limits (knocks, settings)cleaves or fractures easily or is brittle (e.g. rubbed facet edges); wear with care; Corundum is Mohs 9 with excellent toughness and no cleavage, which makes it well suited to rings and other jewellery worn every day; 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.

any treatment state

untreated

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

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

treated (Only after these treatments: dyeing, filling)

treated (Only after these treatments: filling)

treated (Only after these treatments: diffusion treatment)

treated (Only after these treatments: dyeing)

treated (Only after these treatments: heating)

treated (Only after these treatments: irradiation)

Durability and wearing

Toughness

Excellent toughness

Sources GIA Gem Encyclopedia (care guide)

Treatments and identification leads

Registered treatmentsThe treatments registered for Ruby are dyeing, flux-assisted healing, fissure filling with resin, fissure oiling, heat treatment, diffusion treatment and filling, all with status treated. Stability and frequencyDyeing is unstable with occasional market frequency; flux-assisted healing is stable and common; fissure filling with resin is unstable and rare; fissure oiling is unstable and occasional. Identification cluesIdentification leads are also given for dyeing, heat treatment, diffusion treatment and filling, covering respectively colour distribution and colour coming off in solvents; surface melting traces and stress cracks around inclusions; colour concentration and compositional anomalies from chromium or beryllium diffusion; and lustre differences and foreign-element anomalies at filled areas. Values not givenThe stability and market frequency of heat treatment, diffusion treatment and filling, and the identification leads for flux-assisted healing, fissure filling with resin and fissure oiling, are all marked “—”, meaning the cited source gives no value, not “none”.

This table scrolls sideways on narrow screens.

TreatmentMarket frequency (CIBJO)Stability (CIBJO)GB/T 16552 categoryJJA/AGL listingIdentification leads
dyeingStatus: treatedoccasionallyunstableTreatment—See identification leads
flux-assisted healingStatus: treatedcommonlystable———
fissure filling with resinStatus: treatedrarelyunstable———
fissure filling with oilStatus: treatedoccasionallyunstable———
heatingStatus: treated——Optimizationheating; heating, with residues in fissures; heating, with cavities filled by a transparent substanceSee identification leads
diffusion treatmentStatus: treated——Treatmentdiffusion heat treatmentSee identification leads
fillingStatus: treated——Graded — see §5.4.1, Table 1—See identification leads
colouring (JJA category 7, includes dyeing)———colouring (JJA category 7, includes dyeing)—

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

“—” 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 Ruby is set out under report wording on the Corundum entry.

VerifyNames, standards, technical facts, clauses and sources

Names

Standard and listing namesThe GB/T 16552—2017 formal name for Ruby is given in Table A.1, and the suggested listing name is Ruby. Names in four languagesNames are given in four languages: Simplified Chinese, Traditional Chinese, English (Ruby) and Japanese (a katakana transliteration and a kanji name, the GSJ (Japan) formal name); the mineralogical name means the red gem variety of corundum. Institution usageOn authority wording, GIA, the FTC and CIBJO all record Ruby, the FTC wording being in 16 CFR Part 23; Gem-A is unchecked, and bodies without a recorded wording show the entry's own English name, which does not represent their position. The qualifier stripped from the title name is red corundum for GIA and a variety of corundum for CIBJO. National standard namesNational and regional formal names: Germany (RAL) writes Rubin, the EU writes Ruby, India (BIS) writes Ruby/Manik (माणिक), noting that BIS IS 15766 follows CIBJO nomenclature, Thailand (GIT) writes Ruby/Tabtim (ทับทิม), and France (DGCCRF) writes Rubis, with véritable reserved for untreated natural gems.

Authority wording

GIA, FTC, CIBJO, Gem-A
Ruby (on record for GIA, FTC, CIBJO (16 CFR Part 23 §23.25); Gem-A unchecked — bodies without a recorded wording show the entry's own English name)
GSJ (Japan) formal name
ルビー／紅玉
Chinese formal name
红宝石 (GB/T 16552—2017 Table A.1)
Mineralogical name
Red gem variety of corundum

Four-language names

简体中文
红宝石
繁體中文
紅寶石
English
Ruby
日本語
ルビー／紅玉

National and regional formal names

Germany (RAL)
Rubin
European Union
Ruby
India (BIS)
Ruby / Manik (माणिक); BIS IS 15766 refers to CIBJO nomenclature
Thailand (GIT)
Ruby / Tabtim (ทับทิม); GIT certification available
France (DGCCRF)
Rubis; DGCCRF: "véritable" réservé aux pierres naturelles non traitées

Qualifiers stripped from the headline name

  • GIA: (red corundum)
  • CIBJO: (corundum variety)

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 “Ruby” row of GB/T 16552—2017 Annex B, Table B.1 records for Ruby: heating, which improves appearance, in the optimization category; dyeing, which improves or changes colour, in the treatment category; diffusion, which improves colour or produces asterism, in the treatment category; and filling, which improves or changes durability and appearance, with its category set by the grades in GB/T 16552—2017. The notes to Table B.1 and the grade definitions are on the Gem treatments page. JJA/AGL designationsThe list of main gemstone designations in the November 2025 revision of the Japanese JJA/AGL nomenclature records for Ruby: no treatment listed, noting no sign of heating seen, which refers to heat treatment; heating, and heating with residues left in fractures, both recorded as heat treatment; heating with cavities filled with a transparent substance, recorded as heat treatment and filling; diffusion heating, recorded as diffusion; and colouring, recorded as dyeing, noted as including dyeing. How to read the JJA/AGL table is explained on the Gem treatments page.

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

Table B.1, row “Ruby” (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

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
RubyCorundumbrownish red to purplish redno 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)

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

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

What it is and how it's identified

The composition (chemical composition) of Ruby is Al2O3, containing Cr and possibly Fe, Ti, Mn, V and other elements, with the phase corundum; structure crystalline, trigonal, with a hexagonal prismatic or barrel-shaped habit. Mohs hardness 9, no cleavage, though stones with well-developed twinning may show three directions of parting. Density 3.95–4.05 g/cm³, derived from the cited clause value 4.00 and its permitted tolerance of ±0.05. Optical character anisotropic, uniaxial, negative; refractive index 1.757–1.779, derived from the cited clause value 1.762–1.770 and its permitted tolerance of +0.009/−0.005; birefringence 0.008–0.01. Untreated, pleochroism is strong, purplish red and orangy red, and lustre is vitreous to subadamantine. The UV-visible spectrum has absorption peaks at 694 nm, 692 nm, 668 nm and 659 nm, together with an absorption band at 540–620 nm, strong absorption peaks at 476 nm and 475 nm, a weak absorption peak at 468 nm and absorption in the violet region; the infrared spectrum shows characteristic absorption bands from corundum Al-O vibrations in the mid-infrared region.

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

Ruby — composition (chemistry): Al2O3 containing Cr, and possibly also Fe, Ti, Mn, V and other elements.

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

Ruby — composition (phase): corundum

CIBJO Gemmological Laboratories Book 2024

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

Structure

Ruby — 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): §5.1.2 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Ruby — 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): §5.1.2 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Ruby — structure (crystal habit): hexagonal prisms or barrel shapes; a minority are 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): §5.1.2 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Durability

Ruby — 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): §5.1.2 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Ruby — 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): §5.1.2 (locator checked 2026-09-21)
Fact checked on
2026-09-21

For Ruby, the stability of dyeing is “unstable”.

CIBJO Gemstone Book 2022

Treatment state
treated
Treatment
dyeing
Qualification

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

General note
no durability verdict here
Source & check 2026-09-22
Source
Fact checked on
2026-09-22

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

CIBJO Gemstone Book 2022

Treatment state
treated
Treatment
flux-assisted healing
Qualification

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

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

For Ruby, the stability of fissure filling with resin is “unstable”.

CIBJO Gemstone Book 2022

Treatment state
treated
Treatment
fissure filling with resin
Qualification

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

General note
no durability verdict here
Source & check 2026-09-22
Source
Fact checked on
2026-09-22

For Ruby, the stability of fissure filling with oil is “unstable”.

CIBJO Gemstone Book 2022

Treatment state
treated
Treatment
fissure filling with oil
Qualification

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

General note
no durability verdict here
Source & check 2026-09-22
Source
Fact checked on
2026-09-22

Physical properties

Ruby — density: 3.95–4.05 g/cm³

GB/T 16553—2017

0.51.52.53.54.55.56.57.53.95–4.05
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 ±0.05. The range shown here is worked out from that.

Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.1.2 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Optical

Optical effects on record: chatoyancyrepresentative example: cause in Tiger’s Eye (schematic)asterismrepresentative example: cause in Star Sapphire (schematic)

Ruby — 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): §5.1.2 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Ruby — 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): §5.1.2 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Ruby — 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): §5.1.2 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Ruby — pleochroism: strong, purple-red and orange-red

GB/T 16553—2017

Treatment state
untreated
Does this standard apply
applies to this entry
Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.1.2 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Ruby — fluorescence (long-wave UV): weak to strong, red, orange-red

GB/T 16553—2017

UV fluorescence (long-wave UV)redorange-redweak–strongDots 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): §5.1.2 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Ruby — fluorescence (short-wave UV): none to moderate, red, pink-red, orange-red; a few strong, red.

GB/T 16553—2017

UV fluorescence (short-wave UV)redpink-redorange-rednone–moderatea few: redstrongDots 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): §5.1.2 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Ruby — spectrum (UV-visible): 694 nm absorption peak; 692 nm absorption peak; 668 nm absorption peak; 659 nm absorption peak; 540~620 nm absorption band; 476 nm strong absorption peak; 475 nm strong absorption peak; 468 nm weak absorption peak; absorption in the violet region.

GB/T 16553—2017

400450500550600650700 nm468475/476540–620659668692/694
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): §5.1.2 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Ruby — spectrum (infrared): Al-O vibration in corundum gives diagnostic bands in the mid-IR

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

Ruby — optical effect (chatoyancy): seen; rare

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

Ruby — 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): §5.1.2 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Ruby — 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): §5.1.2 (locator checked 2026-09-21)
Fact checked on
2026-09-21

body colour2 sources compared

Ruby — body colour: red, orange-red, purple-red and brown-red

GB/T 16553—2017

Treatment state
untreated
Does this standard apply
applies to this entry
Qualification

The colours GB/T 16553—2017 lists for Synthetic Ruby overlap with this entry: red, orange-red and purplish red.

General note
colour alone is not identity
Source & check 2026-09-26
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.1.2 (locator checked 2026-09-26)
Fact checked on
2026-09-26

Ruby — body colour: purplish red, pinkish red, red, to slightly orangish red.

CIBJO Gemmological Laboratories Book 2024

Treatment state
untreated
Qualification

In chapter 7 of the CIBJO Gemmological Laboratories Book, the colour descriptions of Rubellite, Almandine, Pyrope and other entries also name red or a reddish colour.

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

How the sources relate

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

complementary, no conflict

Both list red, purplish red and an orange-leaning red (GB/T 16553—2017 says orange-red, the CIBJO Gemmological Laboratories Book slightly orangish red). GB/T 16553—2017 also lists brownish red, and the CIBJO book also lists pinkish red.

CIBJO definitions
chatoyancy, asterism

Quality factors

Ruby — 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): §5.1.2 (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.

1.741.761.781.83.73.83.944.14.2Refractive indexSpecific gravity12345Ruby

This material (RI / SG midpoints): 1.768 / 4; 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 gravity12345Ruby

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: §6.1.68.

How far testing can go

Ruby 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): §5.1.2 (dyeing) (locator checked 2026-09-21)
Fact checked on
2026-09-21

Ruby that has undergone heating can be identified by the following features: Under magnification the surface of the stone shows traces of local melting, platy or ring-like stress fissures appear around solid inclusions, negative crystals look corroded or rounded at the rim, and silk and needle inclusions break up into short lengths of silk or fine dots.

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

Ruby that has undergone diffusion treatment can be identified by the following features: What magnification shows resembles a heat-treated stone: chromium-diffused ruby has color concentrated in fissures and hollows, while beryllium-diffused ruby shows surface microcrystallization and recrystallization of its zircon inclusions.

Viewed under magnification in immersion, the color concentrates along the facet edges and the girdle margin in a net-like pattern, though on beryllium-diffused ruby this is mostly indistinct. As to refractive index, chromium-diffused ruby may run as high as 1.788~1.790.

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): §5.1.2 (diffusion treatment) (locator checked 2026-09-22)
Fact checked on
2026-09-22

Ruby 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): §5.1.2 (filling) (locator checked 2026-09-21)
Fact checked on
2026-09-21

Ruby — synthetic counterpart on the market: Synthetic counterparts of this material are common in the trade

CIBJO Gemstone Book 2022

Treatment state
any treatment state
Source & check 2026-09-25
Source
Fact checked on
2026-09-25

For Ruby in trade, the reported frequency of dyeing is “occasionally”.

CIBJO Gemstone Book 2022

Treatment state
treated
Treatment
dyeing
Source & check 2026-09-22
Source
Fact checked on
2026-09-22

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

CIBJO Gemstone Book 2022

Treatment state
treated
Treatment
flux-assisted healing
Source & check 2026-09-25
Source
Fact checked on
2026-09-25

For Ruby in trade, the reported frequency of fissure filling with resin is “rarely”.

CIBJO Gemstone Book 2022

Treatment state
treated
Treatment
fissure filling with resin
Source & check 2026-09-22
Source
Fact checked on
2026-09-22

For Ruby in trade, the reported frequency of fissure filling with oil is “occasionally”.

CIBJO Gemstone Book 2022

Treatment state
treated
Treatment
fissure filling with oil
Source & check 2026-09-22
Source
Fact checked on
2026-09-22

Ruby — what the CIBJO laboratory protocol says to watch for: heat treatment, residues, diffusion, (lead) glass filling, dye, synthetics.

CIBJO Gemmological Laboratories Book 2024

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

Ruby — 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;
Immersion: Be diffusion, synthetic;
DiamondView: Glass filling;
UV-Visible(-NIR) spectroscopy: If necessary for origin;
LA-ICP-MS Chemistry: Be test heated stones, if necessary for origin;
Residue check/ extent: Flux healing;
Clarity enhancement check/extent: Glass filling

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

Ruby is listed in CIBJO Gemmological Laboratories Book 2024 under the term Ruby; the definition gives the mineral species corundum and the mineral/gem variety ruby, with the CIBJO wording quoted in full under Clause-level definitions on this page. The cross-check shows it is defined directly by CIBJO, and Ruby also appears in the GB/T annex.

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TermClauseDefinitionCross-check
Ruby7.2.1.201purplish red, pinkish red, red, to slightly orangish red 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 “Ruby” · Source
IMA Mineral List 2026-07
Listed “Corundum” · Source
CIBJO Gemmological Laboratories Book 2024
Listed §7.2.1.201 “Ruby” · Source

Sources

Further reading

Related pages

Treatments recorded for this material

Recorded cultural contexts

Birthstone list

The U.S. Jewelers of America roster lists Ruby for July; the U.K. National Association of Jewellers chart lists Ruby as traditional for July; and Japan's JJA 2021 revised roster lists Ruby for July. 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, July row: Ruby
Japan Jewellery AssociationJapanfrom 20 December 2021Tanjoseki (Japanese birthstone roster, Japan Jewellery Association page; revision of 20 December 2021)
2021 revised birthstone roster, July row: Ruby
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, July row: Ruby (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 (Ruby) is marked.

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

Who maintains this page

The material facts in the Ruby 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
2026-10-12
Purpose
Lets buyers and sellers check naming, disclosure and material facts clause by clause.

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