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Natural inorganic gem materials · Rock / mineral aggregate · Natural identity; treatment status unknown

Chalcedony

A general term for microcrystalline (cryptocrystalline) quartz aggregates, listed as a basic name in GB/T 16552-2017 Table A.2; dyeing is extremely common. 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 Chalcedony

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

Q1How does chalcedony form?

Silica-rich fluids slowly fill voids or fissures in rock from the rim toward the centre in cycles, depositing chalcedony layer by layer.G&G Fall 2013 · G&G Spring 1982The fluids enter those voids or fissures through microfissures or infiltration canals.G&G Fall 2013 · G&G Spring 1982 +1The number, width and pattern of the layers depend on silica concentration, temperature, pressure and the timing of fluid influxes, while iron, titanium and manganese affect only the colour.G&G Fall 2013 · G&G Spring 1982 +1Besides volcanic cavities, chalcedony also occurs in fissures and pores of sedimentary rocks.G&G Fall 2013 · G&G Spring 1982 +1

Q2What gives chalcedony its colour?

Its colour can be natural, caused by trace colouring elements; for example chromium and nickel produce a bluish green.G&G Winter 2015It ranges from colourless to blue, green, red and brown, sometimes with bands or inclusions, and its colour may be natural or introduced by dyeing.G&G Winter 2015 · G&G Summer 2020 +1Common colours are greyish white, yellow, red, green, blue and purple.GB/T 34098—2017

Q3How can you tell whether chalcedony is genuine?

Not by colour or banding: these do not reveal whether the hue is natural or produced by dyeing or heating, and a trustworthy identification calls for instrumental examination at a qualified gem laboratory.G&G Summer 2014 · CIBJO Gemstone Book 2022Chalcedony has a refractive index of about 1.53–1.54 and a specific gravity of about 2.48–2.65.G&G Summer 2020 · G&G Spring 2020 +1Polished surfaces commonly show a vitreous lustre, and fracture surfaces a greasy or waxy lustre.GB/T 34098—2017Whether one particular bead is natural, treated or synthetic — only a laboratory report can settle that.What this page can answer

Q4Is chalcedony often dyed or heated?

Yes: chalcedony, including blue chalcedony, is commonly dyed to produce or enhance colour.G&G Summer 2020 · G&G Spring 2020Heating is also used to improve its colour, and it is hard to detect.GB/T 16553—2017In dyed chalcedony, magnification shows the colour unevenly distributed, mostly concentrated in fissures, between grains or in surface hollows.GB/T 16553—2017Chalcedony dyed blue or green needs special care, as some fades in light or heat.AGTA Gemstone Information Manual, 17th ed.Whether one particular bead is natural, treated or synthetic — only a laboratory report can settle that.What this page can answer

Q5What is chalcedony, and is it a kind of quartz?

Yes: chalcedony is the cryptocrystalline, or microcrystalline, variety of silica, made mainly of fibrous microcrystalline quartz and also containing other silica forms such as moganite.G&G Fall 2013 · G&G Spring 2020It is a dense, massive cryptocrystalline aggregate, and it can also form spherulitic, radial or finely fibrous aggregates.GB/T 16553—2017

Q6How should you clean chalcedony?

CIBJO's retailer guide says chalcedony can go in an ultrasonic cleaner if it is clear and free of fissures that could weaken it.CIBJO Retailers' Reference Guide (2021)Another source rates ultrasonic and steam cleaning as calling for caution.Gems & Gemology 1987 (Martin)Take special care not to expose it to temperature extremes.CIBJO Retailers' Reference Guide (2021)

Q7Is chalcedony durable enough for everyday jewellery?

Yes: CIBJO's retailer guide calls chalcedony very durable overall, though it should be kept from temperature extremes.CIBJO Retailers' Reference Guide (2021)Prong and bezel settings are rated relatively safe, channel calls for extreme caution, and flush and pavé are best avoided.Gems & Gemology 1987 (Martin)Heat may change its colour.Gems & Gemology 1987 (Martin)

Q8What makes good-quality chalcedony?

CIBJO's reference guide for retailers, which records what collectors favour rather than a grading standard, says unusual banding or landscape-like scenes are particularly prized in chalcedony, as are agates with striking dendritic inclusions.CIBJO Retailers' Reference Guide (2021)Slabs of iris agate and fire agate with strong iridescent colours are also collected.CIBJO Retailers' Reference Guide (2021)

Q9Does chalcedony have healing powers?

There is no scientific evidence that chalcedony 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)

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

Chalcedony is the cryptocrystalline/microcrystalline variety of silica (quartz), composed mainly of fibrous microcrystalline low-α quartz and commonly intergrown with the monoclinic silica phase moganite. It occurs in various volcanic and sedimentary rocks. The prevailing formation model is that voids (vesicles, geodes) or fissures in the host rock are filled cyclically from the rim toward the centre by silica-rich fluids, the silica precipitating as successive layers of fibrous microcrystalline quartz; the shape and width of the zones depend on the silica concentration in the fluids as well as temperature, pressure and the timing of fluid influxes. Impurities such as Fe, Ti and Mn affect only the colour. At the final stage, idiomorphic quartz of different colours may grow in the void centre, and later hydrothermal or hypogenic conditions may incorporate solid inclusions (hematite, goethite, Cu sulfides, calcite). For Sidi Rahal chalcedonic agate specifically, crystallization was induced by Fe3+-rich fluids and lasted millions of years in stages.

Scope: Used to explain the origin of chalcedony (microcrystalline quartz) by silica-rich fluids filling cavities/fractures, and the influence of impurity elements on colour; the colouring mechanism of specific colour varieties must be determined case by case.

Sources G&G Fall 2013 · G&G Spring 1982 · G&G Spring 2020 +2

Where it forms

Voids and vesicles in volcanic rock (geodes, vugs), where silica-rich fluids enter through microfissures or infiltration canals and fill them cyclically.

Sources G&G Fall 2013 · G&G Spring 1982 · G&G Spring 2020

Fissures and pores in sedimentary and other host rocks; chalcedony also occurs in sedimentary rocks.

Sources G&G Fall 2013 · G&G Spring 1982 · G&G Spring 2020

Later hydrothermal and hypogenic settings, where Fe, Cu and Ti phases and other solid inclusions are added after the host rock formed.

Sources G&G Fall 2013 · G&G Spring 2020

How it forms, step by step

  1. Silica-rich fluids penetrate voids or fissures in the rock through microfissures or infiltration canals.

    Sources G&G Fall 2013 · G&G Spring 1982 · G&G Spring 2020

  2. Fluids circulate from the rim toward the centre, precipitating silica as successive layers of fibrous microcrystalline quartz (chalcedony).

    Sources G&G Fall 2013 · G&G Spring 1982 · G&G Spring 2020

  3. The number, width and pattern of the zones depend on silica concentration, temperature, pressure and timing of fluid influxes, while Fe, Ti and Mn affect only the colour.

    Sources G&G Fall 2013 · G&G Spring 1982 · G&G Winter 2015

  4. Later hydrothermal or hypogenic conditions incorporate solid inclusions such as hematite, goethite, Cu sulfides and calcite, and idiomorphic quartz may grow in the centre.

    Sources G&G Fall 2013 · G&G Spring 2020 · G&G Spring 1982

Link to appearance

Waxy lustre and translucency; colours range from colourless to blue, green, red and brown, sometimes with bands or inclusions; colour may be natural (trace elements) or introduced by dyeing.

Sources G&G Winter 2015 · G&G Summer 2020 · G&G Spring 2020

Timescale

Sidi Rahal agate (chalcedonic) crystallization lasted millions of years and proceeded in stages; the moganite-to-low-quartz transformation generally occurs over tens of millions of years and can serve as a relative age indicator.

Sources G&G Fall 2013 · G&G Spring 2020 · G&G Summer 2020 +1

Related base materials

  • Quartz / Silica (SiO2): mineral-group | Chalcedony is the cryptocrystalline/fibrous microcrystalline variety of quartz

Supporting findings

Chalcedony forms as silica-rich fluids slowly fill voids or fissures from the rim toward the centre in cycles, precipitating layer by layer; zone morphology depends on silica concentration, temperature, pressure and the timing of fluid influxes.

Evidence grade A

Scope: Describes vug/fissure-filling formation; vein-type and replacement modes are not covered by the cited sources.

Sources G&G Fall 2013 · G&G Spring 1982

Causes of colour and optical effects

Chalcedony colour can be natural, caused by trace colouring elements, for example a bluish green colour produced by chromium and nickel.

Evidence grade A

Scope: Concerns the studied bluish green chalcedony; colouring elements of other varieties require separate testing.

Sources G&G Winter 2015

How it is identified

For chalcedony, colour and banding by themselves do not reveal whether the hue is natural or produced by dyeing or heating, so visual appearance cannot settle naturalness or treatment; a trustworthy identification and any treatment ruling call for instrumental examination at a qualified gem laboratory, and this entry is no basis for self-testing.

Evidence grade A

Scope: Appearance cannot replace identification; naturalness, dyeing or heat treatment must be determined at a qualified gem laboratory, and this entry is not a self-testing basis.

Sources G&G Summer 2014 · CIBJO Gemstone Book 2022

Other research findings

Chalcedony is the cryptocrystalline/microcrystalline variety of silica (quartz), composed mainly of fibrous microcrystalline low-α quartz and also containing other silica polymorphs such as moganite.

Evidence grade A

Scope: Defines chalcedony's mineral make-up; naming of colour/pattern trade varieties is separate.

Sources G&G Fall 2013 · G&G Spring 2020

Chalcedony has a refractive index of about 1.53–1.54 and specific gravity of about 2.48–2.65; Raman spectroscopy shows it consists of quartz (about 463 cm–1) and moganite (about 501 cm–1).

Evidence grade A

Scope: Measured ranges from GIA laboratory samples; individual specimens may differ slightly.

Sources G&G Summer 2020 · G&G Spring 2020 · G&G Winter 2015

Chalcedony (including blue chalcedony) is commonly dyed to produce or enhance colour, and dyeing must be distinguished from natural colour during identification.

Evidence grade A

Scope: The cited sources document blue dyeing; other dyes and colours need separate verification.

Sources G&G Summer 2020 · G&G Spring 2020

In chalcedony, unusual banding or landscape scenes are particularly prized, as are agates with dramatic dendritic inclusions; slabs of iris agate and fire agate showing strong iridescent colours are also collected.

Evidence grade B

Scope: What collectors favour, as described in a trade association's reference guide; not a grading standard and not a statement about the value of any piece.

Sources CIBJO Retailers' Reference Guide (2021)

Limits of this research

  • Research status: Formation, occurrence or other material-specific findings found in authoritative sources
  • The core source addresses banded chalcedony (agate) and a few blue chalcedony samples; not all chalcedony modes of occurrence and colour varieties are covered.
  • The colouring elements of specific chalcedony varieties (red, brown, green, etc.) must be tested case by case and cannot be generalized from the parent-material model.

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
Chalcedony

GB/T 16552—2017 Table A.2 “Chalcedony(Agate/Jasper)” · CIBJO Gemmological Laboratories Book 2024 §7.2.1.45 “Chalcedony”

Construction or treatment status

Natural identity; treatment status unknown

Treatments recorded for this material: Dyed, Heated / Heat-treated, 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

Chalcedony is often subjected to dyeing. Under GB/T 16552-2017, dyeing counts as an optimization, so the plain gem name may be used (§5.4.2.1 a). Do not assume it is unenhanced.

What this means for you

Before buying, check the recommended listing name "Chalcedony" 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)2 sources compared

Chalcedony — care (cleaning): It can go in an ultrasonic cleaner if it is clear and free of fissures that could weaken it.

CIBJO Retailers' Reference Guide (2021)

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

Chalcedony — care (cleaning): ultrasonic and steamer: use caution.

Gems & Gemology 1987 (Martin)

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

Chalcedony — care (heat): very durable overall, but take special care not to expose it to temperature extremes.

CIBJO Retailers' Reference Guide (2021)

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

Chalcedony — care (light): may fade or revert to its original colour in strong light; do not wear or leave it in strong light for extended periods.

CIBJO Gemstone Book 2022

CIBJO Gemstone Book §6.2:special-care code f

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

Chalcedony — care (special care): dyed blue or green: special care (SC); some fade in light or heat.

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

Chalcedony — care (setting): prong and bezel: relatively safe; channel: use extreme caution; flush and pavé: avoid.

Gems & Gemology 1987 (Martin)

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

Chalcedony — care (repair): pickle pot, polishing and thermal shock: use caution; jeweller's torch: avoid; note: heat may change the colour.

Gems & Gemology 1987 (Martin)

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

Chalcedony — 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 advice for Chalcedony is split by source and treatment state. CIBJOCIBJO states that for Chalcedony in any treatment state, ultrasonic cleaning can be used if the stone is clear and free of fissures that could weaken it; it is very durable to heat overall, but take special care not to expose it to temperature extremes. CIBJO also states that dyed Chalcedony, limited to other colours and to names with a colour prefix, may fade or revert to its original colour in strong light, so do not wear or leave it in strong light for extended periods. LightThe entries from Martin, Gemstone Durability: Design to Display, cover untreated Chalcedony: ultrasonic and steam cleaning need caution; prong and bezel settings are relatively safe, channel setting needs extreme caution, and tension and pavé settings should be avoided; the pickle pot, polishing and thermal shock need caution, and the jeweller's torch should be avoided; heat, sunlight and artificial light in the display case are relatively safe. AGTAAGTA states that Chalcedony dyed blue or green needs special care (marked SC), as some may fade with exposure to light or heat.

This table scrolls sideways on narrow screens.

QuestionMatching entries
Can it go in an ultrasonic or steam cleaner?It can go in an ultrasonic cleaner if it is clear and free of fissures that could weaken it; ultrasonic and steamer: use caution
Heat and thermal shockvery durable overall, but take special care not to expose it to temperature extremes; pickle pot, polishing and thermal shock: use caution; jeweller's torch: avoid; note: heat may change the colour
Light and displayother colours, sold under a colour prefix: may fade or revert to its original colour in strong light; do not wear or leave it in strong light for extended periods; heat in the display case, sunlight and artificial light: relatively safe
Wearing limits (knocks, settings)prong and bezel: relatively safe; channel: use extreme caution; flush and pavé: avoid

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)

Treatments and identification leads

Registered treatmentsThe treatments registered for Chalcedony are heat treatment, dyeing and filling. Heat treatment has status treated, dyeing has status colour treated, and filling has status treated. Values not givenStability and market prevalence for heat treatment, dyeing and filling are all recorded as "—", meaning the cited source gives no value, not "none". Identification cluesAs identification leads: heat treatment improves colour by heating and is difficult to detect; dyed material shows uneven colour distribution under magnification, with dye often concentrated in fissures, between grains or in surface pits; for filling, under magnification the lustre of filled areas differs from that of the host and gas bubbles are present inside, filled areas often fluoresce differently from the host under long-wave and short-wave UV, infrared spectroscopy can show the characteristic absorption bands of the filler, and luminescence imaging instruments such as UV fluorescence viewers can show how the filler is distributed.

This table scrolls sideways on narrow screens.

TreatmentMarket frequency (CIBJO)Stability (CIBJO)GB/T 16552 categoryJJA/AGL listingIdentification leads
heatingStatus: treated——Optimization—See identification leads
dyeingStatus: colour treated——Optimization—See 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): Heated / Heat-treated · Dyed · Filled / Fracture-filled

“—” means the cited source gives no value for that item, not “none”. Source: 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

VerifyNames, standards, technical facts, clauses and sources

Names

Besides Chalcedony, the name register records "Chalcedony", for which no restriction on use as a name is recorded.

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)
ChalcedonyEnglishmarket namematched automaticallyno restriction recordededitorial ruling (no clause cited)

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

Authority wording

GIA, FTC, CIBJO, Gem-A
Chalcedony (on record for CIBJO (CIBJO Gemmological Laboratories Book 2024 §7.2.1.45); 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
カルセドニー／玉髄
Chinese formal name
玉髓 (GB/T 16552—2017 Table A.2, row “Chalcedony(Agate/Jasper)”)
Mineralogical name
Microcrystalline quartz

Four-language names

简体中文
玉髓
繁體中文
玉髓
English
Chalcedony
日本語
カルセドニー／玉髄

National and regional formal names

Germany (RAL)
Chalcedon
European Union
Chalcedony

GB/T 34098 trade names

GB/T 34098-2017 Table A.1 lists these trade names in one cell shared by chalcedony and quartzite jade, agate, jasper; the original does not say which name goes with which: 东陵石 Dongling Shi, 黄龙玉 Huanglong Yu, 南红 Nanhong, 密玉 Mi Yu, 阿拉善玉 Alashan Yu, 通天玉 Tongtian Yu, 台山玉 Taishan Yu, 大别山玉 Dabieshan Yu, 贺州玉 Hezhou Yu, 鸡血玉 Jixue Yu, 金丝玉 Jinsi Yu, 南红玛瑙 Nanhong Manao, and others.

The full table and naming rule are on the Quartzose Jade page.

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

Classification

Origin
Natural materials
Material domain
Natural inorganic gem materials
Browsing family
Quartz and chalcedony materials
Identity tier
Rock / mineral aggregate
Mineral chemical class
Silicates
Construction or treatment status
Natural identity; treatment status unknown

Treatments listed by standards

GB/T Table B.1In the “Chalcedony (Agate/Jasper)” row of GB/T 16552—2017 Annex B, Table B.1, the effect of heating on Chalcedony is to improve or change colour, in the optimization category; filling improves or changes durability and appearance, with its category given by grade; dyeing improves or changes colour, in the optimization category. JJA/AGL designationsThe 2025 revision of the Japanese JJA/AGL Definitions and Nomenclature of Gemstones and Ornamental Materials, in its list of main gemstone designations, places Chalcedony under the species quartz, with colour recorded as other colours (even), and records a no-treatment category; colouring (including dyeing) counts as dyeing. See alsoThe notes to Table B.1 and the definition of each grade are on the Gem treatments page.

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

Table B.1, row “Chalcedony (Agate/Jasper)” (p.16):

This table scrolls sideways on narrow screens.

MethodEffectCategory
HeatingImproves or changes colourOptimization
FillingImproves or changes durability and appearanceGraded — see §5.4.1, Table 1
DyeingImproves or changes colourOptimization

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

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Gem nameSpeciesColourListed in the tableNotes
[colour] ChalcedonyQuartzother colours (uniform)an untreated tier is listed; colouring (JJA category 7, includes dyeing) (Dyed)

JJA/AGL definitions and nomenclature (2025 revision), table of principal gem names, p.11

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

What it is and how it's identified

The material facts for Chalcedony are registered for chalcedony itself; refractive index and hardness carry additional site notes, and the lustre data carry an untreated condition. The composition of Chalcedony is quartz, SiO2, which may contain Fe, Al, Mg, Ca, Na, K, Mn, Ni, Cr and other elements; CIBJO also records the phase as quartz. Its structure is a cryptocrystalline quartz aggregate, compact and fine-textured, fibrous or granular; its crystalline state is a cryptocrystalline aggregate, compact and massive, and may also form spherulitic, radiating or microfibrous aggregates. Mohs hardness 5–7, cleavage none, density 2.5–2.77 g/cm³; the site note on hardness explains that hardness alone is not enough to judge durability. Optical character anisotropic aggregate; refractive index 1.535–1.539, where the site note explains that the clause has finer sub-ranges and the overall value is registered; birefringence not measurable on an aggregate. When untreated, polished surfaces usually show vitreous lustre and fracture surfaces usually show greasy or waxy lustre; the UV-visible spectrum is not diagnostic, and there are infrared absorption bands characteristic of quartz 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

Chalcedony — composition (chemistry): quartz:SiO2, elements such as Fe,Al,Mg,Ca,Na,K,Mn,Ni and Cr may be contained.

GB/T 16553—2017

Does this standard apply
applies to this entry
Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.2.5 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Chalcedony — composition (phase): quartz

CIBJO Gemmological Laboratories Book 2024

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

Structure

Chalcedony — structure (overall): dense, fine-textured cryptocrystalline quartz aggregate whose structure is fibrous or granular.

GB/T 34098—2017

Does this standard apply
applies to this entry
Source & check 2026-09-17
Source
  • GB/T 34098—2017 Quartzose jade — Classification and nomenclature (GB/T): §5.2 (locator checked 2026-09-17)
Fact checked on
2026-09-17

Chalcedony — structure (crystalline state): a cryptocrystalline aggregate, dense and massive in habit; it may also form spherulitic, radial or finely fibrous aggregates.

GB/T 16553—2017

Does this standard apply
applies to this entry
Source & check 2026-09-22
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.2.5 (locator checked 2026-09-22)
Fact checked on
2026-09-22
GB/T 34098—2017 and GB/T 16553—2017

complementary, no conflict

Both entries describe chalcedony as a cryptocrystalline aggregate, from different angles.

GB/T 34098-2017 §5.2 describes its structure (fibrous structure and granular structure), while the crystalline-state field of GB/T 16553-2017 describes the form of the aggregate (dense and massive; it may also be spherulitic, radial or finely fibrous). The two complement each other and do not conflict.

Durability

Chalcedony — Mohs hardness: 5–7

GB/T 16553—2017

123456789105–7References (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): §5.2.5 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Chalcedony — 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): §5.2.5 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Physical properties

Chalcedony — density: 2.5–2.77 g/cm³

GB/T 16553—2017

0.51.52.53.54.55.56.57.52.5–2.77
Specific gravitySource: 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): §5.2.5 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Optical

Optical effects on record: iridescencechatoyancyrepresentative example: cause in Tiger’s Eye (schematic)

Chalcedony — optic character: anisotropic aggregate

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

Chalcedony — refractive index: 1.535–1.539

GB/T 16553—2017

1.31.72.12.52.93.31.535–1.539
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): §5.2.5 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Chalcedony — birefringence: not measurable on an aggregate

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

Chalcedony — pleochroism: not measurable on an aggregate

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

Chalcedony — fluorescence (overall): generally none; sometimes weak to strong, yellow-green.

GB/T 16553—2017

UV fluorescencesometimes: yellow-greenweak–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): §5.2.5 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Chalcedony — spectrum (UV-visible): non-characteristic

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

Chalcedony — spectrum (infrared): Mid-IR absorption follows the pattern typical of quartz

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

Chalcedony — 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): §5.2.5 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Chalcedony — 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): §5.2.5 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Chalcedony — magnification: cryptocrystalline structure, fibre-like texture, conchoidal fracture on the outer surface; agate: banding, ring-like zoning or concentric layering, tiny quartz crystals occasionally seen in the gaps between bands or inside cavities; jasper: packed with mineral impurities, so of granular structure and only semi-translucent to opaque.

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

body colour2 sources compared

Chalcedony — body colour: a variety of colours and textures.

CIBJO Gemmological Laboratories Book 2024

Treatment state
untreated
Qualification

Chapter 7 of the CIBJO Gemmological Laboratories Book sums up the colour of Chalcedony as “a variety of colours”, as it does for Opal and Plastic.

General note
colour alone is not identity
Source & check 2026-09-26
Source
Fact checked on
2026-09-26

Chalcedony — 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 Chalcedony 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): §5.2.5 (locator checked 2026-09-26)
Fact checked on
2026-09-26

How the sources relate

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

consistent

Both sum up the colour of chalcedony as varied (GB/T 16553—2017 says all colours); the CIBJO Gemmological Laboratories Book adds that its textures vary too.

Chalcedony — common colours: greyish white, yellow, red, green, blue, purple and similar colours.

GB/T 34098—2017

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

Among the quartzose jade varieties in GB/T 34098—2017, Quartzite Jade, Agate, Jasper and other varieties also name white or a whitish colour among their common colours; the standard separates these varieties by crystallinity and by whether they show silica-replacement pseudomorphs.

General note
colour alone is not identity
Source & check 2026-09-26
Source
  • GB/T 34098—2017 Quartzose jade — Classification and nomenclature (GB/T): §5.2 (locator checked 2026-09-26)
Fact checked on
2026-09-26
CIBJO definitions
chatoyancy

Quality factors

Chalcedony — quality factor (lustre): Polished surfaces commonly show a vitreous luster. Fracture surfaces commonly show a greasy or waxy luster.

GB/T 34098—2017

Treatment state
untreated
Does this standard apply
applies to this entry
Source & check 2026-09-20
Source
  • GB/T 34098—2017 Quartzose jade — Classification and nomenclature (GB/T): §5.2 (locator checked 2026-09-17)
Fact checked on
2026-09-20

Chalcedony — quality factor (lustre range): vitreous to greasy

GB/T 16553—2017

Treatment state
untreated
Does this standard apply
applies to this entry
Source & check 2026-09-26
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.2.5 (locator checked 2026-09-26)
Fact checked on
2026-09-26
GB/T 34098—2017 and GB/T 16553—2017

complementary, no conflict

The two entries complement each other. GB/T 16553-2017 gives the range of lustre (vitreous to greasy). GB/T 34098-2017 §5.2 describes polished and fracture surfaces separately and also lists a waxy lustre. They do not conflict.

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

1.521.531.541.551.561.572.42.52.62.72.8Refractive indexSpecific gravity12345Chalcedony

This material (RI / SG midpoints): 1.537 / 2.63; Closest values: 1Amethyst 1.548 / 2.67, 2Charoite 1.554 / 2.66, 3Changhua Stone 1.56 / 2.6, 4Shoushan Stone 1.56 / 2.7, 5Balin Stone 1.56 / 2.55

Show the full chart (330 registered materials)1.41.51.61.71.81.922.12.22.32.41234567Refractive indexSpecific gravity12345Chalcedony

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

Chalcedony has identification leads for heat treatment, dyeing and filling. In heat-treated chalcedony, heating is used to improve colour and is hard to detect. In dyed chalcedony, magnification shows uneven colour distribution, with the colorant mostly concentrated in fractures, grain boundaries or surface pits. For filled chalcedony, identification leads include gas bubbles in the filling and a lustre in filled areas different from the stone itself; under long-wave and short-wave UV the filled areas often fluoresce differently from the stone; the infrared spectrum shows the characteristic absorption bands of the filler; and luminescence imaging equipment such as a UV fluorescence viewer can show the distribution of the filler. The heat treatment, dyeing and filling leads given in GB/T 16553—2017 serve only as a reference for the chalcedony entry and do not govern it directly. CIBJO's laboratory rules call for particular checks for dyeing, with a note that the spectroscope is used for green varieties and EDXRF chemical analysis for green varieties. The tests CIBJO's laboratory rules require for chalcedony, and what each method means, are shown in the rules table on the laboratory testing page.

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: §6.1.16.

How far testing can go

Chalcedony that has undergone heating can be identified by the following features: Heating improves the colour; hard to detect.

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

Chalcedony that has undergone dyeing can be identified by the following features: Under magnification the colour is unevenly distributed and mostly concentrated in fissures, between grains or in surface hollows.

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

Chalcedony that has undergone filling can be identified by the following features: Under magnification the surface luster of the filled part differs from the host jade and gas bubbles show in the filled area; under long- and short-wave UV the filled part mostly fluoresces differently from the host jade; infrared spectra show characteristic absorption bands of the filler; luminescence imaging (UV fluorescence viewer and similar) shows how the filler is distributed.

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

Chalcedony — what the CIBJO laboratory protocol says to watch for: dye

CIBJO Gemmological Laboratories Book 2024

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

Chalcedony — 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
Spectroscope: Green variety;
EDXRF chemistry: Green variety

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.

Evidence and sources

Authority basis and clause sources

GB/T 16552—2017
Listed Table A.2 “Chalcedony(Agate/Jasper)” · Source
CIBJO Gemmological Laboratories Book 2024
Listed §7.2.1.45 “Chalcedony” · Source
GB/T 34098—2017
Naming rule Table A.1 · 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 Quartz on this site: 74 entries listed by this site's parent-entry links; synthetic, treated and similar entries carry their recorded state after the name; this page (Chalcedony) is marked.

This table scrolls sideways on narrow screens.

PageContentStatus
Browsing familyQuartz and chalcedony materialsLive
Treatments recorded for this materialDyed, Heated / Heat-treated, Filled / Fracture-filledLive
Related articlesTo be added (placeholder)Planned

Who maintains this page

The material facts in the Chalcedony 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. 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 2026-09-17 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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