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Natural inorganic gem materials · Mineral / gemstone variety · Natural identity; treatment status unknown

Star Ruby

A ruby showing the star effect, usually as a six-rayed star. Synthetic stones and diffusion-induced stars must be disclosed. 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

Care and wear

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

Numbers in curly braces, such as {111}, are crystallographic face symbols (Miller indices): each marks a set of crystal faces or cleavage planes. They are reproduced as written in the cited source.

Star ruby is ruby—red corundum—that shows the phenomenon of asterism: viewed on a cabochon under a point source of light, a star made of light bands appears (usually six rays, occasionally twelve) and shifts as the light moves. This star does not come from any separate mineral; it is produced by needle-shaped rutile (TiO2) inclusions aligned to particular crystallographic directions within the host, which scatter and reflect incoming light and so create the three crossing bands of the six-rayed star. The ruby host grew as corundum at high temperature at depth and owes its red to trace chromium (Cr3+). The rutile needles occupy the corundum's basal plane (0001), each set aligned along the a {1120} direction of the second-order hexagonal prism (equivalent to the three <1010> directions), with the three sets crossing at roughly 60°.

Scope: Applies to explaining the origin of asterism in natural star ruby (scattering/reflection from oriented needle-like inclusions) and the red-corundum nature of its host ruby; does not address synthetic star ruby or treated asterism (for related treatments see the treatment limits).

Sources G&G Fall 2017 · G&G Fall 2019 · G&G Spring 2020

Where it forms

Deep mantle / lower crust: basaltic-type ruby formed under high pressure and very high temperature by partial melting of hybrid mantle material.

Sources G&G Fall 2019

Basaltic magma system: ruby-bearing material was carried rapidly to the surface by basaltic magma, often leaving corrosion features on crystal surfaces.

Sources G&G Fall 2019

Alluvial/eluvial placers: after weathering of the host rock, rubies were transported and concentrated in placer deposits.

Sources G&G Fall 2019

How it forms, step by step

  1. Corundum crystallizes at high temperature at depth from a melt produced by partial melting of mantle material, and trace chromium enters the lattice, coloring the corundum red.

    Sources G&G Spring 2020

  2. During or after growth, titanium is hosted as oriented needle-like rutile (TiO2) inclusions within the basal plane (0001) of the corundum.

    Sources G&G Fall 2017

  3. The needle-shaped inclusions occur as three sets, each aligned along the a {1120} direction of the second-order hexagonal prism, with mutual intersections at roughly 60°.

    Sources G&G Fall 2017

  4. The crystal is carried rapidly to the surface by basaltic magma and later weathered and transported; after fashioning as a cabochon, the oriented needles scatter and reflect light to produce a six-rayed star.

    Sources G&G Fall 2017 · G&G Fall 2019

Link to appearance

Oriented rutile needles scatter and reflect light, producing a six-rayed star of light bands that moves with the light source; needle length, density and orientation control how sharp and bright the star appears.

Sources G&G Fall 2017

Timescale

The available authoritative sources give no growth duration or absolute age for natural star ruby; they discuss basaltic corundum forming at depth at high temperature and rising rapidly with magma, not a timescale for this material.

Sources G&G Fall 2019

Supporting findings

Within natural and synthetic corundum, needles of rutile—or of other TiO2 phases—lie in the basal plane as three sets, each aligned along the a {1120} direction of the second-order hexagonal prism, which is equivalent to the three <1010> directions.

Evidence grade A

Scope: A crystallographic orientation conclusion for the needles, from a 2017 GIA study synthesizing the crystallographic literature.

Sources G&G Fall 2017

Basaltic-type ruby formed by high-temperature partial melting of hybrid mantle material, a deep-seated high-pressure/high-temperature source, and was carried rapidly to the surface by basaltic magma.

Evidence grade B

Scope: Based on inclusion study of the single Bo Welu basaltic deposit in Thailand; not representative of all ruby localities.

Sources G&G Fall 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).

Asia

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

The six-rayed star is formed by needle-like rutile precipitates that scatter and reflect incident light, producing three intersecting light bands.

Evidence grade A

Scope: The mechanism comes from study of needle-like precipitates in asteriated corundum (common to natural and synthetic) and describes the optical cause.

Sources G&G Fall 2017

Ruby’s red color is caused by chromium (Cr3+) in corundum; pure corundum (Al2O3) is itself colorless and transparent, so the color comes from trace chromophores.

Evidence grade A

Scope: An authoritative quantitative conclusion on corundum’s causes of color, applicable to the ruby host color.

Sources G&G Spring 2020

How it is identified

A star ruby's asterism is striking but is not proof of natural origin, and natural, synthetic and glass-filled star corundum must be told apart by laboratory work. Laboratories combine several lines of evidence: magnification of inclusions and growth features; routine tests such as refractive index, specific gravity and polariscope behaviour; ultraviolet fluorescence; and spectroscopy (for example FTIR, UV-Vis-NIR and Raman). Trace-element chemistry measured by EDXRF or LA-ICP-MS helps separate natural from synthetic corundum and, compared with a reference collection, may point to a geographic origin; glass-filled fractures and coatings are caught by clues such as anomalous luster, gas bubbles, X-ray radiography, and FTIR or EDXRF signatures. Origin calls can remain inconclusive, so the finding should be issued by a qualified gem laboratory.

Evidence grade A

Scope: Applies where natural, synthetic and treated corundum, and geographic origin, must be assessed; no self-administered criteria are given.

Sources G&G Summer 1998 · G&G Winter 2019 · G&G Fall 2019 +2

Origin labels for star ruby (Myanmar or Mozambique, for instance) are often used to support a premium, yet origin cannot be inferred from appearance or name. Origin determination is a comparison against reference databases of known localities: a laboratory measures trace-element suites by LA-ICP-MS and weighs inclusion features such as rutile silk, clouds, and growth zoning against specimens of documented provenance. The judgement is relative - the characteristic ranges of different localities overlap, deposits with no reference material cannot be assigned, and a single deposit is internally variable; heating and other treatments alter the measurable features, so treatment status must be settled first, and an individual stone may therefore return an "inconclusive" result. An origin call must be issued by an accredited laboratory for a specific specimen, and "consistent with a locality" is not the same as "mined there".

Evidence grade A

Scope: Origin cannot be inferred from appearance or name; conclusions are probabilistic and must be issued by an accredited laboratory for a specific specimen; no self-test criteria are given here.

Sources G&G Winter 2019 · G&G Spring 2015

Other research findings

Heat treatment may be applied to ruby and sapphire, whether natural or synthetic, for several purposes: to strengthen asterism, to eliminate asterism or silk, and to enhance, introduce or take away colour.

Evidence grade A

Scope: A general statement on the effects of heat treatment by an industry authority (Nassau, GIA); it gives no specific process parameters.

Sources G&G Fall 1981

Limits of this research

  • Research status: Formation, occurrence or other material-specific findings found in authoritative sources
  • The asterism mechanism comes from study of oriented rutile needles common to natural and synthetic material; the cited sources do not distinguish whether natural ruby needles are primary or exsolution-related.
  • The deep formation environment for basaltic ruby comes from a single Thai deposit study and is not representative of all localities.
  • No absolute timescale for natural star ruby is given by the cited sources.

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
Star Ruby

GB/T 16552—2017 5.3.2 · IMA Mineral List 2026-07 “Corundum”

Construction or treatment status

Natural identity; treatment status unknown

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

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

The asterism must be a genuine optical effect; synthetic material and diffusion-induced stars must be disclosed.

Evidence

  • GB/T · 5.3.2

What this means for you

Before buying, check the recommended listing name "Star 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.

The item-by-item care advice that the GIA Care and Cleaning Guide gives for the whole class, and so for Star Ruby, is set out in full under care on the Ruby entry.

Care

care (cleaning)2 sources compared

Star 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
Source & check 2026-09-25
Source
Fact checked on
2026-09-25

Star 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

Star Ruby — care (cleaning): ultrasonic and steamer: avoid; 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

Star 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
Source & check 2026-09-25
Source
Fact checked on
2026-09-25

Star 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
Source & check 2026-09-25
Source
Fact checked on
2026-09-25

Star 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

Star 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

Star 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

Star Ruby — care (repair): pickle pot and polishing: relatively safe; thermal shock: use caution; jeweller's torch: avoid; 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

Star 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

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

Care conclusions for Star Ruby vary with treatment state and scope. TreatedFor treated Star Ruby (dyed or with oil-filled fractures only), the CIBJO Blue Book records that it must not be cleaned ultrasonically, that dyeing, oiling, resin, wax and plastic impregnation are not permanent, so keep it away from all solvents, chemicals and heat, and that it breaks easily when worn, so take care; Martin's Gemstone Durability: Design to Display states for oiled or dyed stones that cleaning should avoid solvents, repairs should avoid heat, and polishing needs care. UntreatedFor untreated stones, Martin states that ultrasonic and steam cleaning should be avoided and polishing compounds may enter surface-reaching inclusions or fractures; for setting, prong, bezel, tension, channel and pavé are relatively safe, with extra care for stones with strong twinning, fractures or many inclusions; in repairs, pickling after soldering and polishing are relatively safe, thermal shock needs care, the torch should be avoided, very high heat may change the colour, and borax-containing flux or pickle may etch the surface; and in display, display-case heat, sunlight and artificial light are relatively safe.

This table scrolls sideways on narrow screens.

QuestionMatching entries
Can it go in an ultrasonic or steam cleaner?care (cleaning); oiled or dyed stones: avoid solvents; ultrasonic and steamer: avoid; note: polishing compound can get into inclusions or fractures that reach the surface
Heat and thermal shockoiled or dyed stones: avoid heat and take care in polishing; pickle pot and polishing: relatively safe; thermal shock: use caution; jeweller's torch: avoid; 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
Contact with acids, alkalis and household chemicalsTreatments with dye, oil, resin, wax or plastic are not permanent; keep it away from all solvents (including dish-washing liquids), chemicals and heat
Wearing limits (knocks, settings)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

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

treated (Only after these treatments: diffusion treatment)

Durability and wearing

Toughness

Excellent

Sources GIA Gem Encyclopedia (care guide)

Treatments and identification leads

Registered treatmentsThe treatments registered for Star Ruby are heating, dyeing, filling, diffusion and oiled fissures, all with status treated. Stability and frequencyHeating and diffusion have stability stable, while dyeing, filling and oiled fissures have stability not stable. On market prevalence, heating, dyeing and diffusion are all rare, filling is common and oiled fissures are occasional. Values not givenThe identification leads and sources for each treatment are recorded as "—", meaning the cited source gives no value, not "none". SyntheticsAccording to the registered entries, synthetic Star Ruby is common on the market.

This table scrolls sideways on narrow screens.

TreatmentMarket frequency (CIBJO)Stability (CIBJO)GB/T 16552 categoryJJA/AGL listingIdentification leads
heatingStatus: treatedrarelystableOptimizationheating (any colour)—
dyeingStatus: treatedrarelyunstableTreatment——
fillingStatus: treatedcommonlyunstableGraded — see §5.4.1, Table 1——
diffusion treatmentStatus: treatedrarelystableTreatmentdiffusion heat treatment (any colour)—
fissure filling with oilStatus: treatedoccasionallyunstable———
impregnation with a colourless agent (oil or resin)———impregnation with a colourless agent (oil or resin) (any colour)—
colouring (JJA category 7, includes dyeing)———colouring (JJA category 7, includes dyeing) (any colour)—
lead-glass impregnation———lead-glass impregnation (asterism + lead glass (as written in the colour column))—

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

“—” means the cited source gives no value for that item, not “none”. Source: CIBJO Gemstone Book 2022; GB/T 16552—2017 Table B.1 (row for Ruby); 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 Star Ruby is set out under report wording on the Corundum entry.

VerifyNames, standards, technical facts, clauses and sources

Names

Recommended listing nameThe suggested listing name for Star Ruby is Star Ruby, built by the naming rules of GB/T 16552—2017 with the basic name Ruby; the GB/T 16552—2017 text does not list Star Ruby separately. Names in four languagesThe four-language names are given in Simplified Chinese, Traditional Chinese, English (Star Ruby) and Japanese (a transliteration). Trade and mineralogical namesThe mineralogical name is recorded as Ruby (corundum) showing asterism, usually as a six-rayed star. Institution usageAmong authority wordings, the body on record is CIBJO, which writes Star Ruby (CIBJO Gemmological Laboratories Book 2024); the FTC source text has no wording for this name (checked); the wordings of GIA and Gem-A have not been checked; bodies without a recorded wording show the entry's own English name, which does not represent their position. Japanese namesOn the Japanese side, the entry's own Japanese name is a transliteration, and the Japanese GSJ wording for Star Ruby is not yet verified by this site.

Authority wording

GIA, FTC, CIBJO, Gem-A
Star Ruby (on record for CIBJO (CIBJO Gemmological Laboratories Book 2024); no wording for this name in the FTC text on file; GIA, Gem-A unchecked — bodies without a recorded wording show the entry's own English name)
GSJ (Japan) formal name
スター・ルビー (not yet checked for this body — the entry's own Japanese name is shown)
Name built by the GB/T naming rules (not listed as such)
星光红宝石 (GB/T 16552—2017 §5.3.2; basic name 红宝石)
Mineralogical name
Ruby (corundum) displaying asterism (usually 6-rayed)

Four-language names

简体中文
星光红宝石
繁體中文
星光紅寶石
English
Star Ruby
日本語
スター・ルビー

See also: Misleading and prohibited trade names · Supplementary name index

Classification

Origin
Natural materials
Material domain
Natural inorganic gem materials
Browsing family
Oxide minerals
Identity tier
Mineral / gemstone variety
Mineral chemical class
Oxides / hydroxides
Construction or treatment status
Natural identity; treatment status unknown

Treatments listed by standards

GB/T Table B.1Treatments for Star Ruby are shown under the Ruby row of GB/T 16552—2017 Annex B, Table B.1: heating is listed as optimization, dyeing as treatment, filling by grades, and diffusion as treatment; the notes to Table B.1 and the definitions of the filling grades are on the Gem treatments page. JJA/AGL designationsIn the table of principal gem names in the JJA/AGL (Japan) definitions and nomenclature, November 2025 revision, Star Ruby / [colour] Star Sapphire has an untreated tier listed; heating is recorded as heated, diffusion heating as diffusion treated, impregnation with a colourless agent (oil or resin) as filled, and colouring as dyed, noting that this includes dyeing; Star Ruby/Star Sapphire + Lead Glass has no untreated tier listed, and impregnation with lead glass is recorded as filled.

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

Under the “Ruby” row of Table B.1: Heating Optimization; Dyeing Treatment; Filling Graded — see §5.4.1, Table 1; Diffusion Treatment. The full row, with the effect column, is on the Ruby page.

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

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

This table scrolls sideways on narrow screens.

Gem nameSpeciesColourListed in the tableNotes
Star Ruby / [colour] Star SapphireCorundumany colouran untreated tier is listed; heating (Heated / Heat-treated); diffusion heat treatment (Diffusion-treated); impregnation with a colourless agent (oil or resin) (Filled / Fracture-filled); colouring (JJA category 7, includes dyeing) (Dyed)asterism; adding the colour variety is optional
Star Ruby/Star Sapphire + Lead GlassCorundum+lead glassasterism + lead glass (as written in the colour column)the source lists no untreated tier; lead-glass impregnation (Filled / Fracture-filled)asterism; named “star ruby / star sapphire + lead glass”

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

The composition (phase) of Star Ruby is corundum. Registered for ruby as a whole (regardless of origin), Star Ruby is crystalline, trigonal, with a hexagonal prismatic or barrel-shaped habit, occasionally tabular or bladed; Mohs hardness is 9, with no cleavage, though well-twinned stones may show parting in three directions. Registered for ruby as a whole (regardless of origin), density is 3.95–4.05 g/cm³, worked out from the clause value 4.00 and tolerance of ±0.05; refractive index is 1.757–1.779, worked out from the clause value 1.762–1.770 and tolerance of +0.009, −0.005; birefringence is 0.008–0.01; optic character is anisotropic, uniaxial, optically negative. Registered for ruby as a whole (regardless of origin), untreated, pleochroism is strong, purplish red and orange-red, and the quality factor (lustre) is vitreous to subadamantine. Registered for ruby as a whole (regardless of origin), chatoyancy is visible but rare, and asterism is visible, commonly as six-rayed stars.

Registered material facts

Each row carries its own source and check date and can be cited on its own; “—” means the cited source gives no value, not “none”.

Chemical composition, long-wave UV luminescence, short-wave UV luminescence, UV-visible spectrum, infrared spectrum, magnification: these whole-class features are given in the cited clause for ruby as a whole (not one origin), so they are not repeated on the Star Ruby page; see the material facts on the Ruby entry.

Items below that name the class they cover give the cited clause’s value for that whole class, not a measurement of Star Ruby (how to read class-level values).

Definition

Star Ruby — composition (phase): corundum

CIBJO Gemmological Laboratories Book 2024

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

Structure

Star Ruby — structure (overall): crystalline

GB/T 16553—2017

Does this standard apply
applies to this entry
What this covers
ruby as a whole (not one origin)
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

Star Ruby — structure (crystal system): trigonal

GB/T 16553—2017

Does this standard apply
applies to this entry
What this covers
ruby as a whole (not one origin)
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

Star 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
What this covers
ruby as a whole (not one origin)
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

Durability

Star 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
What this covers
ruby as a whole (not one origin)
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

Star 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
What this covers
ruby as a whole (not one origin)
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

For Star Ruby, the stability of heating is “stable”.

CIBJO Gemstone Book 2022

Treatment state
treated
Treatment
heating
Qualification

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

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

For Star 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 Star Ruby itself is.

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

For Star Ruby, the stability of filling is “unstable”.

CIBJO Gemstone Book 2022

Treatment state
treated
Treatment
filling
Qualification

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

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

For Star Ruby, the stability of diffusion treatment is “stable”.

CIBJO Gemstone Book 2022

Treatment state
treated
Treatment
diffusion treatment
Qualification

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

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

For Star 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 Star Ruby itself is.

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

Physical properties

Star 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
What this covers
ruby as a whole (not one origin)
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 2026-09-26
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.1.2 (locator checked 2026-09-26)
Fact checked on
2026-09-26

Optical

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

Star Ruby — optic character: uniaxial, optically negative (anisotropic)

GB/T 16553—2017

Does this standard apply
applies to this entry
What this covers
ruby as a whole (not one origin)
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

Star 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
What this covers
ruby as a whole (not one origin)
Qualification

The clause we cite gives 1.762–1.770, with a stated tolerance of +0.009 / -0.005. The range shown here is worked out from that.

Source & check 2026-09-26
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.1.2 (locator checked 2026-09-26)
Fact checked on
2026-09-26

Star 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
What this covers
ruby as a whole (not one origin)
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

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

GB/T 16553—2017

Treatment state
untreated
Does this standard apply
applies to this entry
What this covers
ruby as a whole (not one origin)
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

Star Ruby — optical effect (chatoyancy): seen; rare

GB/T 16553—2017

Does this standard apply
applies to this entry
What this covers
ruby as a whole (not one origin)
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

optical effect (asterism)2 sources compared

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

GB/T 16553—2017

Does this standard apply
applies to this entry
What this covers
ruby as a whole (not one origin)
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

Star Ruby — optical effect (asterism): asterism.

CIBJO Gemmological Laboratories Book 2024

Source & check 2026-09-22
Source
Fact checked on
2026-09-22
CIBJO definitions
chatoyancy, asterism

Quality factors

Star Ruby — quality factor (lustre): vitreous to subadamantine

GB/T 16553—2017

Treatment state
untreated
Does this standard apply
applies to this entry
What this covers
ruby as a whole (not one origin)
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

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 gravity12345Star Ruby

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 gravity12345Star Ruby

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

Star Ruby is identified as ruby: the CIBJO laboratory protocol places Star Ruby under “Ruby”, the identification part is in the Ruby entry, and the required tests are listed on the laboratory testing page. Synthetic counterparts of Star Ruby are common on the market. According to CIBJO, among treated Star Ruby, heat treatment occurs with a prevalence of “rare”, dyeing “rare”, filling “common”, diffusion “rare” and fracture filling with oil “occasional”.

The CIBJO laboratory protocol covers Star Ruby under “Ruby” (§6.1.68): see identification on the Ruby entry; the required tests are listed on the CIBJO laboratory protocol table for Ruby.

How far testing can go

Star 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 Star Ruby in trade, the reported frequency of heating is “rarely”.

CIBJO Gemstone Book 2022

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

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

CIBJO Gemstone Book 2022

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

For Star Ruby in trade, the reported frequency of filling is “commonly”.

CIBJO Gemstone Book 2022

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

For Star Ruby in trade, the reported frequency of diffusion treatment is “rarely”.

CIBJO Gemstone Book 2022

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

For Star 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

Each row's “Source & check” expands to the full source; the date beside it is the fact check date.

Clause-level definitions

Star Ruby has a corresponding entry in the CIBJO Gemmological Laboratories Book 2024 under the name Star ruby; its visible definition gives the mineral species as corundum and the mineral/gem variety as Star ruby, with the CIBJO wording quoted in full under Clause-level definitions on this page. The cross-check result is that it is defined directly by CIBJO, and no identically named English entry was found in this edition of the GB/T annex.

This table scrolls sideways on narrow screens.

TermClauseDefinitionCross-check
Star ruby7.2.1.229Ruby showing asterism (usually a six-ray star, sometimes a twelve-ray star)Defined directly by CIBJO; no identically named English entry was found in this edition of the GB/T annex.

Evidence and sources

Authority basis and clause sources

GB/T 16552—2017
Not listed the name does not occur anywhere in the text; scope: Chapter 1 “Scope” · Source
GB/T 16552—2017
Naming rule 5.3.2 · Source
IMA Mineral List 2026-07
Listed “Corundum” · Source
CIBJO Gemmological Laboratories Book 2024
Listed §7.2.1.229 “Star ruby” · Source

Sources

Further reading

Related pages

Treatments recorded for this material

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 (Star Ruby) is marked.

This table scrolls sideways on narrow screens.

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

Who maintains this page

The material facts in the Star 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 2026-09-22 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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