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Artificial products / Manufactured products · Artificial product type · Man-made glass

Glass

Also known asCrystal glass (conditional name)

Man-made glass material. GB/T 16552-2017 Annex A Table A.5 lists it as a basic name for artificial gems, and it cannot be called natural rock crystal or a natural gem. Also known as Crystal glass. 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 RalphReviewed by JuneLast updated 2026-10-12Who maintains this page

FAQCare and wear

Questions people ask about Glass

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

Q1Is my bead a real gemstone or just glass?

Glass has been used to imitate gems since ancient times, and because it can be made in essentially any hue it stands in for many gems, including amethyst, aquamarine and peridot.GIA Introduction to Imitation GemsIt is less brilliant than the gems it imitates, but appearance alone cannot prove what a piece is.CIBJO Gemstone Book 2022Glass is amorphous, not crystalline.GB/T 16553—2017Whether one particular bead is natural, treated or synthetic — only a laboratory report can settle that.What this page can answer

Q2Are some glass beads coated, and how does the coating show?

Yes, some glass is coated: on coated glass, the surface lustre looks abnormal under magnification and the film can be seen peeling off in places.GB/T 16553—2017On coated glass, refractive index readings may also be abnormal, and infrared and Raman spectra show the film's characteristic peaks.GB/T 16553—2017

Q3How should you clean glass beads?

Only plain glass that shows no deterioration (no weeping, crizzling or flaking) may be washed in clean, lukewarm water, and it should then air-dry slowly, never with heat.CCI Notes 5/1Glass should not go in a dishwasher or be cleaned with abrasive pads or scouring cleaners.AIC Objects Specialty Group Postprints (Koob, 2004)Cleaning products that contain fragrance or ammonia should be avoided.AIC Objects Specialty Group Postprints (Koob, 2004)

Q4Do glass beads break or chip easily?

Yes: glass is hard yet brittle and readily cracks or shatters when struck.CCI Notes 5/1Mechanical damage accounts for most harm to glass, which breaks and chips easily; moisture is the chief chemical cause of deterioration, and how susceptible a glass is depends heavily on its original composition.NPS Museum Handbook, Appendix PSudden swings in temperature can also crack or break it.CCI Notes 5/1

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

Glass is a non-crystalline material that has solidified from a melt and as a rule comprises a blend of oxides (for example those of silicon, sodium, calcium, aluminium and lead). As a gem material, this entry treats 'man-made glass' as an artificial-product category: man-made glass has served as a gem imitation since ancient times, and because it can be produced in essentially any hue it stands in for a wide range of gems. Note: this entry and the Man-made Glass entry describe the same kind of material and can be read together; both are distinct from natural glass (see the Natural Glass entry, e.g. obsidian) — natural glass forms by natural processes, whereas man-made glass is manufactured.

Scope: Applies to explaining the definition, naming and imitation uses of man-made glass as a category of artificial product, and its relationship to the Man-made Glass entry and the Natural Glass entry; does not apply to any description of natural genesis.

Sources CIBJO Gemstone Book 2022 · GIA Introduction to Imitation Gems

Where it forms

Manufacturing environment: a man-made furnace/factory setting in which oxide feedstock is melted and then cooled to solidify; no natural occurrence environment applies to this record.

Sources CIBJO Gemstone Book 2022 · GIA Introduction to Imitation Gems

Not applicable to a natural occurrence environment: this entry covers man-made glass; the occurrence environment of natural glass (see the Natural Glass entry, e.g. obsidian) is not conflated with this entry.

Sources CIBJO Gemstone Book 2022 · GIA Introduction to Imitation Gems

How it forms, step by step

  1. Prepare an oxide feedstock mixture (e.g. silicon, sodium, calcium, aluminium and lead oxides).

    Sources GIA Introduction to Imitation Gems

  2. Heat the feedstock to a molten state.

    Sources GIA Introduction to Imitation Gems

  3. Cool and solidify the melt into amorphous glass, which can be made in various colors.

    Sources GIA Introduction to Imitation Gems

  4. Shape or cut into finished imitation gems, or use fused layers to imitate the look of agate, malachite, tortoise shell, etc.

    Sources GIA Introduction to Imitation Gems

Link to appearance

Glass's appearance as an imitation comes from its ability to be made in virtually any color and to be fused in layers, though it is less brilliant; appearance alone cannot prove identity.

Sources CIBJO Gemstone Book 2022

Timescale

The source states that manufactured glass is an age-old gem imitation but gives no specific date or process duration.

Sources CIBJO Gemstone Book 2022

Supporting findings

Man-made glass has served as a gem imitation since ancient times. Because it can be produced in essentially any hue, it stands in for a wide range of gems — amethyst, aquamarine and peridot among them — and can also mimic tiger's eye and opal, while fused layers imitate agate, malachite or tortoiseshell.

Evidence grade A

Scope: Applies to the manufactured nature and imitative use of glass; not to natural origin.

Sources GIA Introduction to Imitation Gems

How it is identified

Coloured glass of various opacities can imitate almost any coloured gemstone; faceted colourless glass is one of the oldest diamond imitations, and glass beads coated with pearlescent paint are a common pearl imitation. Moulded glass can also mimic optical effects: in one laboratory case, glass cabochons sold as star sapphire had a star moulded in and fixed in place rather than a genuine star.

Evidence grade A

Scope: These are general features of glass imitations reported in laboratory notes on other gems, not a test specific to this material; any single piece can only be identified by a gemmological laboratory.

Sources G&G Fall 2021

Gas bubbles and flow structure are recurring microscope features of manufactured glass imitations. In one case two prisms resembling copper-bearing Paraíba tourmaline showed trapped gas bubbles, flow structure and a boundary where two glasses were fused; another note warns that gas bubbles, while typical of glass, may also occur in amber, so further testing can be needed.

Evidence grade A

Scope: These are general features of glass imitations reported in laboratory notes on other gems, not a test specific to this material; any single piece can only be identified by a gemmological laboratory.

Sources G&G Winter 2020 · G&G Fall 2019

Other research findings

Glass is a non-crystalline material that has solidified from a melt and as a rule comprises a blend of oxides (for example those of silicon, sodium, calcium, aluminium and lead).

Evidence grade A

Scope: Applies to the physical-state and composition definition of glass (CIBJO covers both natural and artificial); not to a specific specimen.

Sources CIBJO Gemstone Book 2022

Under CIBJO, artificial uncrystallised products include man made glass and lead glass, and shall be named by the correct name of the composing material (e.g. 'glass') or by the imitated material's name preceded by the word 'imitation'.

Evidence grade A

Scope: Applies to naming and disclosure of man-made glass; not to specific contract terms.

Sources CIBJO Gemstone Book 2022

This entry (Glass) and the Man-made Glass entry describe the same kind of material, man-made glass, and can be read together; both should be clearly distinguished from the Natural Glass entry (natural glass, e.g. obsidian): natural glass forms by natural processes, whereas man-made glass is manufactured.

Evidence grade A

Scope: Explains how this entry relates to Man-made Glass and Natural Glass; it is not a ruling on whether any entry should be merged or removed.

Sources CIBJO Gemstone Book 2022

Lead glass is artificially produced glass with a distinctly high content of lead oxide, and is a sub-type of man-made glass.

Evidence grade A

Scope: Applies to lead glass as a sub-type of man-made glass; not to any specimen's lead content.

Sources CIBJO Gemstone Book 2022

Limits of this research

  • Research status: Formation, occurrence or other material-specific findings found in authoritative sources
  • CIBJO clause 5.40's definition of 'glass' covers both natural and artificial glass, so man-made glass must be distinguished by context; this record covers only the man-made glass category.
  • The cited sources give no specific formulation or process parameters for man-made glass.

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
Glass beads

GB/T 16552—2017 Table A.5 “Glass” · CIBJO Gemstone Book 2022 5.40

Construction or treatment status

Man-made glass

Treatments recorded for this material: Filled / Fracture-filled

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

Glass is often subjected to filling. It is a man-made material: under GB/T 16552-2017 §5.4.2.2 d), treated man-made gems may be named by their basic man-made name.

Evidence

  • GB/T · Table A.5, row 玻璃 (Glass)

What this means for you

Before buying, check the recommended listing name "Glass beads" and any disclosed treatments on this page, and ask the seller for a grading report if in doubt.

Known uncertainty

  • This entry's exact material identity is not fully settled.
  • See “Disclosure and cautions” above
  • Disclosure rules for the treatments above can change as authorities update their standards; re-check before relying on this page.
Last reviewed
2026-09-01

Trade-name ruling

  • Not a mineral: man-made or non-mineral material.
Suggested listing name
Glass beads

Care and wear

Care

care (cleaning)2 sources compared

Glass — care (cleaning): only plain glass that shows no deterioration (no weeping, crizzling or flaking) may be washed in clean, lukewarm water; after washing, let glass air-dry slowly; never speed drying with heat.

CCI Notes 5/1

Treatment state
any treatment state
Source & check 2026-10-06
Source
Fact checked on
2026-10-06

Glass — care (cleaning): Never put glass through a dishwasher: within a few years the surface turns cloudy and etched; do not clean glass objects in a dishwasher or with abrasive pads or scouring cleaners.

AIC Objects Specialty Group Postprints (Koob, 2004)

Treatment state
any treatment state
Source & check 2026-10-06
Source
Fact checked on
2026-10-06

Glass — care (heat): Do not apply heat to glass or leave it where sun or spotlights can warm it noticeably; keep glass away from temperature extremes and above all from sudden swings, which can crack or break it.

CCI Notes 5/1

Treatment state
any treatment state
Source & check 2026-10-06
Source
Fact checked on
2026-10-06

care (light)2 sources compared

Glass — care (light): Colourless glass decolourized with manganese can turn purple under ultraviolet exposure (solarization); this applies to that glass type only.

CCI Notes 5/1

Treatment state
any treatment state
Source & check 2026-10-06
Source
Fact checked on
2026-10-06

Glass — care (light): sunlight falling directly on unstable glass heats it locally, sharply lowering the surrounding RH, which dries it out and causes crizzling.

CCI Preventive Conservation Guidelines (2018)

Treatment state
any treatment state
Source & check 2026-10-06
Source
Fact checked on
2026-10-06

care (chemicals)2 sources compared

Glass — care (chemicals): Avoid cleaning glass with products that contain fragrance or ammonia

AIC Objects Specialty Group Postprints (Koob, 2004)

Treatment state
any treatment state
Source & check 2026-10-06
Source
Fact checked on
2026-10-06

Glass — care (chemicals): On glass already starting to crizzle, water and alkaline cleaners like soap or detergent can worsen deterioration unless fully removed.

CCI Preventive Conservation Guidelines (2018)

Treatment state
any treatment state
Source & check 2026-10-06
Source
Fact checked on
2026-10-06

care (storage)2 sources compared

Glass — care (storage): For glass that is already deteriorating, an abrupt fall in RH below 40% or rise above 60% can cause damage.

CCI Notes 5/1

Treatment state
any treatment state
Source & check 2026-10-06
Source
Fact checked on
2026-10-06

Glass — care (storage): CCI recommends holding glass at 40 to 50 percent relative humidity

CCI Preventive Conservation Guidelines (2018)

Treatment state
any treatment state
Source & check 2026-10-06
Source
Fact checked on
2026-10-06

care (wear)2 sources compared

Glass — care (wear): Glass is hard yet brittle and readily cracks or shatters when struck

CCI Notes 5/1

Treatment state
any treatment state
Source & check 2026-10-06
Source
Fact checked on
2026-10-06

Glass — care (wear): Mechanical damage accounts for most harm to glass; it breaks and chips easily; moisture is the chief chemical cause of glass deterioration, with susceptibility depending heavily on the original composition.

NPS Museum Handbook, Appendix P

Treatment state
any treatment state
Source & check 2026-10-06
Source
Fact checked on
2026-10-06

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?only plain glass that shows no deterioration (no weeping, crizzling or flaking) may be washed in clean, lukewarm water; after washing, let glass air-dry slowly; never speed drying with heat; Never put glass through a dishwasher: within a few years the surface turns cloudy and etched; do not clean glass objects in a dishwasher or with abrasive pads or scouring cleaners
Heat and thermal shockDo not apply heat to glass or leave it where sun or spotlights can warm it noticeably; keep glass away from temperature extremes and above all from sudden swings, which can crack or break it
Light and displayColourless glass decolourized with manganese can turn purple under ultraviolet exposure (solarization); this applies to that glass type only; sunlight falling directly on unstable glass heats it locally, sharply lowering the surrounding RH, which dries it out and causes crizzling
Contact with acids, alkalis and household chemicalsAvoid cleaning glass with products that contain fragrance or ammonia; On glass already starting to crizzle, water and alkaline cleaners like soap or detergent can worsen deterioration unless fully removed
Wearing limits (knocks, settings)Glass is hard yet brittle and readily cracks or shatters when struck; Mechanical damage accounts for most harm to glass; it breaks and chips easily; moisture is the chief chemical cause of glass deterioration, with susceptibility depending heavily on the original composition

Treatments and identification leads

One row per treatment, with three standards side by side: how often it occurs and how stable it is (CIBJO), its category in GB/T 16552—2017 Table B.1 (this site's paraphrase) and how the JJA/AGL 2025 table lists it. Each CIBJO value links to its entry under “Testing and market”, where the wording and source are given in full.

This table scrolls sideways on narrow screens.

TreatmentMarket frequency (CIBJO)Stability (CIBJO)GB/T 16552 categoryJJA/AGL listingIdentification leads
coatingStatus: treated————See identification leads

Where each treatment acts (schematics): Coated

“—” means the cited source gives no value for that item, not “none”. Source: GB/T 16553—2017

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

VerifyNames, standards, technical facts, clauses and sources

Names

Besides Glass, the name register records "Crystal glass", for which no restriction on use as a name is recorded; one further name in a non-Latin script is listed in the name register below (1 that must not be used as a name).

Standard and listing namesThe Chinese formal name for Glass comes from GB/T 16552—2017 Table A.5; the mineralogical name is Man-made glass, meaning glass manufactured artificially; the trade name/synonym is Crystal glass, which must match the facts and local rules, is matched as a market name only once the condition is confirmed, and has no restriction recorded on its use as a name. The suggested listing name is glass bead. Names in four languagesNames are given in Simplified Chinese, Traditional Chinese, English (Glass) and Japanese; the Japanese name is the entry's own, and the wording used by GSJ (Japan) for Glass is not yet verified by this site. Institution usageThe wording of GIA, FTC, CIBJO and Gem-A is not yet verified by this site for any of them; Glass is shown as the entry's own English name and does not represent the position of GIA, FTC, CIBJO or Gem-A. Trade and mineralogical namesAustrian diamond is a market name but must not be used as a name; GB/T 16552—2017 uses Austrian diamond as an example to show that artificial products must not be given confusing or ambiguous names, and Austrian diamond is not a trade name.

Name register

Every name recorded for this entry, with how it is classified, whether it may be matched to this entry automatically, whether it may be used as a product name, and the clause it rests on.

This table scrolls sideways on narrow screens.

NameTypeMatchingUse as a nameBasis
no restriction recorded (1)
Crystal glassEnglishmarket namematched only once the condition is confirmedno restriction recordededitorial ruling (no clause cited)
not to be used as a name (1)
奥地利钻石Simplified Chinesemarket namematched automaticallynot to be used as a nameGB/T 16552—2017 5.1.3.2 c); GB/T 16552—2017 5.1.3.2 a); Note: GB/T 16552—2017 §5.1.3.2 c) uses it as the example of a rule: artificial products must not be given confusing or ambiguous names (a counter-example, not a trade name); the material is glass.

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

Authority wording

GIA, FTC, CIBJO, Gem-A
Glass (not yet checked by this site — the entry's own English name is shown)
GSJ (Japan) formal name
ガラス (not yet checked for this body — the entry's own Japanese name is shown)
Chinese formal name
玻璃 (GB/T 16552—2017 Table A.5)
Mineralogical name
Man-made glass
Trade names and synonyms
Crystal glass (market name; conditional name)

Four-language names

简体中文
玻璃
繁體中文
玻璃
English
Glass
日本語
ガラス

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

Classification

Origin
Artificial products / Manufactured products
Material domain
Artificial products / Manufactured products
Browsing family
Man-made glass products
Identity tier
Artificial product type
Mineral chemical class
Not applicable
Construction or treatment status
Man-made glass

What it is and how it's identified

The material facts for Glass are registered from GB/T 16553—2017 Gems — Testing: the composition is mainly SiO2, and Na, Fe, Al, Mg, CO (so printed in the standard; probably cobalt, Co), Pb and rare earth elements may be present; the structure is amorphous, and cleavage none. Mohs hardness 5–6 and density 2.3–4.5 g/cm³; this site notes that the cited clause gives typical values, common readings rather than absolute limits, and that hardness alone is not enough to judge durability. Optic character isotropic, often with anomalous optical behaviour; refractive index 1.47–1.7, which this site notes is the overall value registered although the clause has finer sub-ranges; birefringence none. Untreated Glass has no pleochroism and a vitreous lustre.

Registered material facts

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

Definition

Glass — composition (chemistry): largely SiO2; rare earth elements, Na, Fe, Al, Mg, CO (so printed in the standard; probably Co) and Pb may be present.

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

Structure

Glass — structure (overall): amorphous (not 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): §5.4.20 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Durability

Glass — Mohs hardness: 5–6

GB/T 16553—2017

123456789105–6References (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
Qualification

The clause we cite gives this as a typical value. It is a common value, not an absolute limit.

General note
hardness only, not durability
Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.4.20 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Glass — cleavage: none

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

Physical properties

Glass — density: 2.3–4.5 g/cm³

GB/T 16553—2017

0.51.52.53.54.55.56.57.52.3–4.5
Specific gravitySource: GB/T 16553—2017
Does this standard apply
applies to this entry
Qualification

The clause we cite gives this as a typical value. It is a common value, not an absolute limit.

Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.4.20 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Optical

Optical effects on record: play of colourrepresentative example: cause in Opal (schematic)iridescencechatoyancyrepresentative example: cause in Tiger’s Eye (schematic)asterismrepresentative example: cause in Star Sapphire (schematic)aventurescencerepresentative example: cause in Sunstone (schematic)colour changelabradorescencerepresentative example: cause in Labradorite (schematic)

Glass — optic character: isotropic, commonly with anomalous optical behaviour

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

Glass — refractive index: 1.47–1.7

GB/T 16553—2017

1.31.72.12.52.93.31.47–1.7
Refractive indexSource: GB/T 16553—2017
Does this standard apply
applies to this entry
General note
the clause has finer ranges
Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.4.20 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Glass — birefringence: none

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

Glass — pleochroism: none

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

Glass — fluorescence (overall): weak to strong; varies with colour; short wave is usually stronger than long wave.

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

Glass — spectrum (UV-visible): non-characteristic; varies with the colouring element

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

Glass — spectrum (infrared): The mid-IR spectrum shows the band pattern typical of glass

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

Glass — optical effect (play of colour): seen

GB/T 16553—2017

Does this standard apply
applies to this entry
Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.4.20 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Glass — optical effect (iridescence): seen

GB/T 16553—2017

Does this standard apply
applies to this entry
Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.4.20 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Glass — optical effect (chatoyancy): seen

GB/T 16553—2017

Does this standard apply
applies to this entry
Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.4.20 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Glass — optical effect (asterism): seen

GB/T 16553—2017

Does this standard apply
applies to this entry
Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.4.20 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Glass — optical effect (aventurescence): seen

GB/T 16553—2017

Does this standard apply
applies to this entry
Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.4.20 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Glass — optical effect (colour change): seen

GB/T 16553—2017

Does this standard apply
applies to this entry
Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.4.20 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Glass — optical effect (labradorescence): seen

GB/T 16553—2017

Does this standard apply
applies to this entry
Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.4.20 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Glass — magnification: bubble, long, empty tube-shaped cavities, flow line, "orange peel" surface, rounded edges between facets, devitrified texture, honeycomb structure.

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

Glass — body colour: occurs in many colors

GB/T 16553—2017

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

GB/T 16553—2017 sums up the colour of Glass as “all colours”; in its chapter 5, Tourmaline, Calcite, Opal and other variety clauses likewise say “all colours” or “all body colours”.

General note
colour alone is not identity
Source & check 2026-09-26
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.4.20 (locator checked 2026-09-26)
Fact checked on
2026-09-26
CIBJO definitions
play of colour, chatoyancy, asterism, aventurescence, colour change, labradorescence

Quality factors

Glass — quality factor (lustre): vitreous

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): §5.4.20 (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.

1.581.61.621.641.663.13.23.33.43.5Refractive indexSpecific gravity12345Glass

This material (RI / SG midpoints): 1.585 / 3.4; Closest values: 1Hemimorphite 1.625 / 3.45, 2Imperial Topaz 1.623 / 3.53, 3Lazulite 1.627 / 3.12, 4Apatite 1.639 / 3.18, 5Synthetic Jadeite 1.66 / 3.34

Show the full chart (330 registered materials)1.41.51.61.71.81.922.12.22.32.41234567Refractive indexSpecific gravity12345Glass

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

After coating, Glass under magnification shows abnormal surface lustre and the film peeling off in places; refractive index readings may be abnormal; and infrared and Raman spectra show characteristic peaks of the film. The status of coating is treated, and the cited GB/T 16553—2017 can be followed only as a reference for the Glass entry and does not directly govern it.

How far testing can go

Glass that has undergone coating can be identified by the following features: Under magnification the surface luster is abnormal and the film can be seen peeling off in places; refractive index readings may be abnormal; infrared and Raman spectra show characteristic peaks of the film.

GB/T 16553—2017

Treatment state
treated
Does this standard apply
can be followed as a reference only
Treatment
coating
Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.4.20 (coating) (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.

Clause-level definitions

The clause-level definition of Glass is in GB/T 16552-2017 Annex A, under the term Glass, defined as Man-made glass. The cross-check result is that it is listed directly in GB/T, and no identically titled standalone entry was found in CIBJO.

This table scrolls sideways on narrow screens.

TermClauseDefinitionCross-check
GlassGB/T 16552-2017 Annex AMan-made glassListed directly by GB/T; CIBJO carries no standalone entry under the same name.

Evidence and sources

Authority basis and clause sources

GB/T 16552—2017
Listed Table A.5 “Glass” · Source
CIBJO Gemstone Book 2022
Naming rule 5.40 · 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.

This table scrolls sideways on narrow screens.

PageContentStatus
Browsing familyMan-made glass productsLive
Treatments recorded for this materialFilled / Fracture-filledLive
Related articlesTo be added (placeholder)Planned

Who maintains this page

The material facts in the Glass 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
Ralph
Reviewer
June
How facts are checked
Each fact is matched to the clause it cites; facts checked between 2026-09-21 and 2026-10-06
Last revised
2026-10-12
Purpose
Lets buyers and sellers check naming, disclosure and material facts clause by clause.

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