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Natural inorganic gem materials · Trade name: colour / appearance variety · Natural identity; treatment status unknown
Onyx (banded chalcedony)
Also known asOnyx
Chalcedony with straight, parallel black and white bands; CIBJO Gemmological Laboratories Book 2024 §7.2.1.160 narrows the term to this meaning, and the black goods it lists are all dyed. 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.
Questions people ask about Onyx (banded chalcedony)
Every sentence below is followed by the registered fact it rests on; answers add no new facts and promise no outcome.
Q1Is black onyx dyed?
Onyx, especially black onyx, is commonly dyed to get a uniform dark colour, so black should not be assumed natural and should be treated as a treated material when it is identified.G&G Fall 2013 · G&G Summer 2020 +1Colour and banding alone do not reveal whether the colour is natural or produced by dyeing or heating; that takes instrumental examination.G&G Summer 2014 · CIBJO Gemstone Book 2022
Q2What exactly is onyx?
Onyx is a banded chalcedony, a kind of agate, with parallel bands.G&G Fall 2013CIBJO describes it as straight, parallel black and white layers.CIBJO Gemmological Laboratories Book 2024
Q3How can you tell if onyx is real?
Onyx is translucent chalcedony with parallel black-and-white or coloured bands, and its black may be natural or introduced by dyeing.G&G Fall 2013 · G&G Summer 2020 +1Appearance cannot settle whether a piece is natural or treated; a trustworthy identification needs instrumental examination.G&G Summer 2014 · CIBJO Gemstone Book 2022Whether one particular bead is natural, treated or synthetic — only a laboratory report can settle that.What this page can answer
Q4What creates the bands in onyx?
The number, width and pattern of the bands depend on silica concentration, temperature, pressure and the timing of fluid influxes, while iron, titanium and manganese affect only their colour.G&G Fall 2013Red-brown and red bands are coloured by iron compounds such as hematite.G&G Fall 2013
Q5How does onyx form?
It forms in voids and gas cavities in volcanic rock and in fissures in sedimentary rock, which silica-rich fluids fill again and again.G&G Fall 2013The fluids deposit silica layer by layer from the rim toward the centre as fibrous microcrystalline quartz, building up the bands.G&G Fall 2013
Q6What does onyx symbolize, and does it have protective or healing powers?
There is no scientific evidence that onyx 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 is recorded is its long use in ornament: museum collections hold banded chalcedony beads from Middle Kingdom Egypt around 1981–1640 B.C. and Roman-period necklace beads and cameos.The Met 15.3.81 · The Met 64.64 +4
Sources cited in these answers ASA/CAP guidance (UK)
What this page can answer
This page covers
- How Onyx (banded chalcedony) forms and what gives its colourFormation setting, process and timescale; where its colour and optical effects come from, each finding graded and sourced
- How to identify Onyx (banded chalcedony)Identification points from the research literature; how far lab testing can go
- Treatments and enhancements of Onyx (banded chalcedony)The enhancements and treatments the GB/T and JJA/AGL tables list
- Hardness, density and refractive index of Onyx (banded chalcedony)Each value with its source and check date
- Onyx (banded chalcedony) in English, Chinese and Japanese; national standard namesNames in four languages, the GB/T standard name and the suggested listing name; and: Which of GIA, FTC, CIBJO and Gem-A have a name for it on record, and do those agree?
- Name origin and history of Onyx (banded chalcedony)How people have used it, with museum objects
- Listing and disclosing Onyx (banded chalcedony)The listing name to use; what must be disclosed before sale
- Standard clauses that define Onyx (banded chalcedony)Which clause defines it, each cross-checked
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
Onyx is a form of banded chalcedony (agate) characterised by roughly parallel black-and-white or coloured bands, and its genesis follows agate: voids in the rock are filled cyclically from the rim toward the centre by silica-rich fluids, the silica precipitating layer by layer as fibrous microcrystalline quartz (chalcedony) to form the bands. The number, width and pattern of the bands depend on the silica concentration in the fluids as well as temperature, pressure and the timing of fluid influxes; Fe, Ti and Mn and Fe compounds affect only the colour of the bands, with red-brown bands coloured by hematite. At the final stage coloured idiomorphic quartz may grow in the void centre. Commercially, onyx (especially black) is often dyed to obtain a uniform dark colour and must be treated as a treated material.
Scope: Used to explain the cavity-filling origin of onyx as banded chalcedony and the elemental sources of colour in its bands, with an identification note that black onyx is commonly dyed.
Sources G&G Fall 2013 · G&G Summer 2020 · G&G Spring 2020
- Agates from Morocco: Gemological Characteristics and Proposed Origin (Gems & Gemology, Fall 2013, Vol. 49, No. 3)
- Quench-Crackled Dyed Blue Chalcedony Resembling Larimar (Gems & Gemology, Summer 2020, Vol. 56, No. 2, Lab Notes)
- Dyed Chalcedony Imitation of Chrysocolla-in-Chalcedony (Gems & Gemology, Spring 2020, Vol. 56, No. 1)
Where it forms
Voids and vesicles in volcanic rock (geodes, vugs) and fissures in sedimentary rocks, where silica-rich fluids fill them cyclically to form banded chalcedony.
Sources G&G Fall 2013
Fluid settings bearing Fe and other impurity elements, which govern the colour of the individual bands.
Sources G&G Fall 2013
How it forms, step by step
Silica-rich fluids penetrate voids in the rock through microfissures or infiltration canals.
Fluids circulate from the rim toward the centre, precipitating silica layer by layer as fibrous microcrystalline quartz (chalcedony) to form parallel/concentric bands.
Band number, width and pattern depend on silica concentration, temperature, pressure and timing of influxes, while Fe, Ti, Mn and Fe compounds determine colour.
Commercially, onyx (especially black) is often dyed for a uniform dark colour and must be treated as treated material during identification.
Sources G&G Fall 2013 · G&G Summer 2020 · G&G Spring 2020
- Agates from Morocco: Gemological Characteristics and Proposed Origin (Gems & Gemology, Fall 2013, Vol. 49, No. 3)
- Quench-Crackled Dyed Blue Chalcedony Resembling Larimar (Gems & Gemology, Summer 2020, Vol. 56, No. 2, Lab Notes)
- Dyed Chalcedony Imitation of Chrysocolla-in-Chalcedony (Gems & Gemology, Spring 2020, Vol. 56, No. 1)
Link to appearance
Translucent chalcedony with parallel black-and-white or coloured bands; bands form through pulsed silica-rich filling and impurity-element colouration, and black may be natural or introduced by dyeing.
Sources G&G Fall 2013 · G&G Summer 2020 · G&G Spring 2020
- Agates from Morocco: Gemological Characteristics and Proposed Origin (Gems & Gemology, Fall 2013, Vol. 49, No. 3)
- Quench-Crackled Dyed Blue Chalcedony Resembling Larimar (Gems & Gemology, Summer 2020, Vol. 56, No. 2, Lab Notes)
- Dyed Chalcedony Imitation of Chrysocolla-in-Chalcedony (Gems & Gemology, Spring 2020, Vol. 56, No. 1)
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
Related base materials
- Agate: banded form | Onyx is a type of banded chalcedony (agate) with parallel colour bands
- Chalcedony: mineral-base | Composed of microcrystalline quartz (chalcedony)
Supporting findings
Onyx is a form of banded chalcedony (agate) with parallel bands; its genesis is the void-filling mechanism of banded chalcedony.
Evidence grade AScope: The morphological distinction between parallel and concentric bands is a gemmological/classical naming convention not defined in the cited source.
The number, width and pattern of the bands depend on silica concentration plus temperature, pressure and the timing of fluid influxes; Fe, Ti and Mn affect only the colour of the bands.
Evidence grade AScope: The prevailing hypothesis for banded chalcedony; the precise banding mechanism is still debated.
Causes of colour and optical effects
Red-brown/red bands are coloured by Fe compounds such as hematite.
Evidence grade AScope: Concerns the Fe-bearing red bands; colourless/grey-white bands follow other mechanisms.
Human use and museum objects
Collection evidence shows the banded chalcedony parent material (onyx/agate) used as beadwork by Middle Kingdom Egypt around 1981-1640 B.C. (Met 15.3.81) and later as necklace beads and cameos in the Roman period (Met 95.16.13, 2021.40.72). This evidence pertains to the chalcedony/agate parent material and does not establish onyx as an independent material.
Evidence grade AScope: Applies to collection objects labelled onyx/sardonyx, whose material belongs to the chalcedony (agate) parent; other chalcedony varieties are not covered, nor does it establish onyx as an independent material.
Sources The Met 15.3.81 · The Met 64.64 · The Met 95.16.13 +3
- The Metropolitan Museum of Art — Round bead (15.3.81)
- The Metropolitan Museum of Art — Eye bead (?) (64.64)
- The Metropolitan Museum of Art — Gold, emerald, carnelian, banded onyx, and garnet necklace (95.16.13)
- The Metropolitan Museum of Art — Sardonyx cameo (2021.40.72)
- The Metropolitan Museum of Art — Sardonyx cameo (41.160.430)
- The Metropolitan Museum of Art — Bead (34.107.111)
Onyx is a banded variety of chalcedony (agate), not an independent material; the collection evidence cited here under museum labels 'onyx' and 'sardonyx' therefore belongs to the parent chalcedony/agate material. The earliest instance is a Middle Kingdom Egyptian round bead (Met 15.3.81, ca. 1981-1640 B.C., Memphite Region, labelled onyx) and a Neo-Babylonian 'eye bead' (Met 64.64, ca. 7th century BCE, Mesopotamia, labelled onyx). The Roman period adds a gold necklace with banded onyx (95.16.13, 1st century CE) and numerous sardonyx cameos (e.g. 2021.40.72, ca. 1st century CE; 41.160.430, 1st century BCE-3rd century CE, Roman), carved through the banded colour layers. Sasanian Iran also yields beads labelled sardonyx or carnelian (34.107.111, ca. 3rd-7th century CE). All this evidence pertains to the chalcedony/agate parent material.
Sources The Met 15.3.81 · The Met 64.64 · The Met 95.16.13 +3
- The Metropolitan Museum of Art — Round bead (15.3.81)
- The Metropolitan Museum of Art — Eye bead (?) (64.64)
- The Metropolitan Museum of Art — Gold, emerald, carnelian, banded onyx, and garnet necklace (95.16.13)
- The Metropolitan Museum of Art — Sardonyx cameo (2021.40.72)
- The Metropolitan Museum of Art — Sardonyx cameo (41.160.430)
- The Metropolitan Museum of Art — Bead (34.107.111)
Scope: A museum object evidences only the existence and date of that artefact itself; it does not establish widespread ancient use of the material, nor does it attest the origin, naturalness, or treatment of any modern specimen.
Objects cited
- The Met 15.3.81Onyx
- The Met 64.64Onyx
- The Met 95.16.13Gold, emerald, carnelian, banded onyx, with central cabochon garnet
- The Met 2021.40.72Sardonyx
- The Met 41.160.430Sardonyx
- The Met 34.107.111Sardonyx or carnelian
How it is identified
For onyx, 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 AScope: 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
Onyx (especially black) is commonly dyed to obtain a uniform dark colour; black must not be assumed natural and should be identified as a treated material.
Evidence grade BScope: Sources document many dyes for chalcedony and blue-dyeing examples; black onyx dyeing is trade practice but is not directly documented in the cited sources.
Sources G&G Fall 2013 · G&G Summer 2020 · G&G Spring 2020
- Agates from Morocco: Gemological Characteristics and Proposed Origin (Gems & Gemology, Fall 2013, Vol. 49, No. 3)
- Quench-Crackled Dyed Blue Chalcedony Resembling Larimar (Gems & Gemology, Summer 2020, Vol. 56, No. 2, Lab Notes)
- Dyed Chalcedony Imitation of Chrysocolla-in-Chalcedony (Gems & Gemology, Spring 2020, Vol. 56, No. 1)
Limits of this research
- Research status: Formation, occurrence or other material-specific findings found in authoritative sources
- The authoritative source discusses banded chalcedony collectively as 'agate' and does not define the 'parallel bands' description specific to onyx.
- Black onyx dyeing is not directly documented in the cited sources and remains a treatment claim requiring further evidence.
Methodology
- Origin determination and its limits
- Quality grading and value factors
- How gemmology became a technical discipline
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
- Onyx (banded chalcedony)
GB/T 16552—2017 5.1.1 c) · CIBJO Gemmological Laboratories Book 2024 §7.2.1.160 “Onyx”
Construction or treatment status
Natural identity; treatment status unknown
Treatments recorded for this material: Heated / Heat-treated (via parent material), Filled / Fracture-filled (via parent material), Dyed
Related:Disclosure and cautions
This page cannot answer
Natural? · Origin · Price
A lab report settles these; this wiki covers naming and disclosure.
Related:What this page can answer
Answer at a glance
Onyx (banded chalcedony) is Onyx: straight, parallel black-and-white banded chalcedony; use "Onyx (banded chalcedony)" for listings, and disclose any known treatments.
Evidence
- CIBJO · 7.2.1.160
What this means for you
Before buying, check the recommended listing name "Onyx (banded 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
No care facts are recorded for this entry itself. Its parent material has care records: see Quartz.
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.
| Treatment | Market frequency (CIBJO) | Stability (CIBJO) | GB/T 16552 category | JJA/AGL listing | Identification leads |
|---|---|---|---|---|---|
| Heating | — | — | Optimization | — | — |
| Filling | — | — | Graded — see §5.4.1, Table 1 | — | — |
| Dyeing | — | — | Optimization | — | — |
| colouring (JJA category 7, includes dyeing) | — | — | — | colouring (JJA category 7, includes dyeing) | — |
“—” means the cited source gives no value for that item, not “none”. Source: GB/T 16552—2017 Table B.1 (row for Chalcedony); 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 Onyx (banded chalcedony), the name register records "Onyx", for which no restriction on use as a name is recorded (CIBJO Gemmological Laboratories Book 2024 §7.2.1.160 “Onyx”); one further name in a non-Latin script is listed in the name register below (1 with no restriction recorded on use as a name).
Standard and listing namesOnyx (banded chalcedony) is not listed in the text of GB/T 16552—2017; its GB/T naming counterpart is agate in the chalcedony (agate/jasper) row of Table A.2, and the suggested listing name is Onyx. Names in four languagesNames are given in Simplified Chinese, Traditional Chinese, English (Onyx (banded chalcedony)) and Japanese; the mineralogical description is chalcedony with straight, parallel black and white bands. The GSJ (Japan) wording for this name is not yet verified by this site, and the entry's own Japanese name is shown. Institution usageOn authority wording, CIBJO records Onyx, there is no wording for this name in the FTC text on file (checked), and the wording of GIA and Gem-A is not yet verified by this site; unchecked bodies show the entry's own English name, which does not represent their position. Trade and mineralogical namesIn the name register, Onyx is an English market name that can be aligned automatically. Candidate search termsA Japanese transliteration is only a candidate search term, per the JJA/AGL (Japan) gem name handbook 2025; black agate is listed as a related high-risk name: in English mineralogy Onyx is banded chalcedony, and black material on the market is often dyed agate, which must be disclosed.
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.
| Name | Type | Matching | Use as a name | Basis |
|---|---|---|---|---|
| no restriction recorded (2) | ||||
| OnyxEnglish | market name | matched automatically | no restriction recorded | CIBJO Gemmological Laboratories Book 2024 §7.2.1.160 “Onyx”; Note: Related high-risk name “Black Onyx”: in mineralogy onyx is banded chalcedony; black onyx on the market is usually dyed agate and must be disclosed. |
| オニックスJapanese | transliteration | search candidate only | no restriction recorded | JJA/AGL Gemstone Nomenclature 2025 p.11 |
How each authority words this name: see Names › Authority wording.
- GSJ (Japan) formal name
- オニキス／縞瑪瑙 (not yet checked for this body — the entry's own Japanese name is shown)
- GB/T naming counterpart (this name is not in the standard)
- 玛瑙 (GB/T 16552—2017 Table A.2, row “Chalcedony(Agate/Jasper)”)
- Mineralogical name
- Onyx: straight, parallel black-and-white banded chalcedony
- Trade names and synonyms
- Onyx (market name)
Four-language names
- 简体中文
- 缟玛瑙
- 繁體中文
- 縞瑪瑙
- English
- Onyx (banded chalcedony)
- 日本語
- オニキス／縞瑪瑙
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
- Trade name: colour / appearance variety
- Mineral chemical class
- Silicates
- Construction or treatment status
- Natural identity; treatment status unknown
Treatments listed by standards
GB/T Table B.1For Onyx (banded chalcedony), this site applies the “Chalcedony (agate/jasper)” row of GB/T 16552—2017 Annex B, Table B.1; the treatments applied are heating (classed as optimization), filling (classed by grades, each defined on this site's Gem treatments page) and dyeing (classed as optimization). JJA/AGL designationsThe Japanese JJA/AGL 2025 designations list Onyx under the species name quartz, with the colour given as straight black-and-white bands, note that the cited original has no “no treatment” entry, and record colouring (including dyeing) as dyeing. GB/T Table B.1What Table B.1 notes, how the filling grades are defined and how to read the JJA/AGL table are all explained on this site's Gem treatments page, and the full Table B.1 row including the effect column is on the Chalcedony entry.
GB/T 16552-2017, Annex B, Table B.1
Under the “Chalcedony (Agate/Jasper)” row of Table B.1: Heating Optimization; Filling Graded — see §5.4.1, Table 1; Dyeing Optimization. The full row, with the effect column, is on the Chalcedony 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 name | Species | Colour | Listed in the table | Notes |
|---|---|---|---|---|
| Onyx | Quartz | straight black-and-white bands | the source lists no untreated tier; 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
Onyx (banded chalcedony) is composed of quartz (phase), with a body colour of straight, parallel black and white layers, for the untreated state, both from the Onyx definition in the CIBJO Blue Book 2024; this site notes that in Chapter 7 of the CIBJO Blue Book the colour descriptions of entries such as charoite, howlite and opal also mention black or blackish tones. Structure, Mohs hardness, cleavage, density, optic character, refractive index, birefringence and lustre take the values of the cited GB/T 16553—2017 clause for chalcedony (including agate and jasper, the whole class): a cryptocrystalline aggregate, dense and massive, and may also be spherulitic, radial or finely fibrous; Mohs hardness 5–7; cleavage none; density 2.5–2.77 g/cm³; optic character anisotropic aggregate; refractive index 1.535–1.539, and this site notes that the clause has finer ranges, so the overall value is used for Onyx; birefringence not measurable on an aggregate; lustre vitreous to greasy, for the untreated state.
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, luminescence, UV-visible spectrum, infrared spectrum, magnification: these whole-class features are given in the cited clause for chalcedony, including agate and jasper (the whole class), so they are not repeated on the Onyx (banded chalcedony) page; see the material facts on the Chalcedony entry.
Items below that name the class they cover give the cited clause’s value for that whole class, not a measurement of Onyx (banded chalcedony) (how to read class-level values).
Definition
Onyx — composition (phase): quartz
CIBJO Gemmological Laboratories Book 2024
Source & check 2026-09-22
- Source
- Fact checked on
- 2026-09-22
Structure
Onyx — structure (overall): 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
- What this covers
- chalcedony, including agate and jasper (the whole class)
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
Durability
Onyx — Mohs hardness: 5–7
GB/T 16553—2017
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))
- Does this standard apply
- applies to this entry
- What this covers
- chalcedony, including agate and jasper (the whole class)
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
Onyx — cleavage: none
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- chalcedony, including agate and jasper (the whole class)
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
Physical properties
Onyx — density: 2.5–2.77 g/cm³
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- chalcedony, including agate and jasper (the whole class)
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
Optical
Onyx — optic character: anisotropic aggregate
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- chalcedony, including agate and jasper (the whole class)
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
Onyx — refractive index: 1.535–1.539
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- chalcedony, including agate and jasper (the whole class)
- General note
- the clause has finer ranges
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
Onyx — birefringence: not measurable on an aggregate
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- chalcedony, including agate and jasper (the whole class)
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
Onyx — pleochroism: not measurable on an aggregate
GB/T 16553—2017
- Treatment state
- untreated
- Does this standard apply
- applies to this entry
- What this covers
- chalcedony, including agate and jasper (the whole class)
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
Onyx — optical effect (iridescence): seen
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- chalcedony, including agate and jasper (the whole class)
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
Onyx — optical effect (chatoyancy): seen
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- chalcedony, including agate and jasper (the whole class)
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
Onyx — body colour: straight, parallel black and white layers.
CIBJO Gemmological Laboratories Book 2024
- Treatment state
- untreated
- Qualification
In chapter 7 of the CIBJO Gemmological Laboratories Book, the colour descriptions of Charoite, Howlite, Opal and other entries also name black or a blackish colour.
- General note
- colour alone is not identity
Source & check 2026-09-26
- Source
- Fact checked on
- 2026-09-26
- CIBJO definitions
- chatoyancy
Quality factors
Onyx — quality factor (lustre): vitreous to greasy
GB/T 16553—2017
- Treatment state
- untreated
- Does this standard apply
- applies to this entry
- What this covers
- chalcedony, including agate and jasper (the whole class)
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
Each row's “Source & check” expands to the full source; the date beside it is the fact check date.
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)
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
Testing and market
The CIBJO laboratory protocol covers Onyx (banded chalcedony) under “Chalcedony” (§6.1.16): see identification on the Chalcedony entry; the required tests are listed on the CIBJO laboratory protocol table for Chalcedony.
How far testing can go
Each row's “Source & check” expands to the full source; the date beside it is the fact check date.
Clause-level definitions
Onyx (banded chalcedony) is defined directly in the CIBJO Gemmological Laboratories Book 2024 under the entry name Onyx, as chalcedony consisting of straight, parallel black and white layers. Cross-check result: defined directly by CIBJO; the same English name was not found directly in the GB/T annex of this edition.
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| Term | Clause | Definition | Cross-check |
|---|---|---|---|
| Onyx | 7.2.1.160 | Chalcedony composed of straight, parallel black and white layers | 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
Sources
Further reading
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 (Onyx (banded chalcedony)) is marked.
- Quartz
Sub-entries (57)
- Agate
Sub-entries (1)
- Amethyst
- Ametrine
- Aventurine Quartz
- Aventurine Quartz / Green Aventurine
- Banded Agate
- Black Agate
- Bloodstone / Heliotrope
- Blue Lace Agate
- Carnelian
- Chalcedony
Sub-entries (2)
- Chrysoprase
- Citrine
- Clear Quartz / Rock Crystal
- Coated Quartz
- Colourless to White Quartz (brand name: Azeztulite)
- Crazy Lace Agate
- Dendritic Agate
- Dyed Agate (Treated: dyed)
- Elestial Quartz / Skeletal Quartz
- Eye Agate
- Flower Agate / Cherry Blossom Agate
- Green Quartz
- High-clarity quartz with golden needle-like inclusions
- Included Quartz
- Jasper
Sub-entries (1)
- Madeira Citrine
- Malachite Agate
- Morion / very dark Smoky Quartz
- Moss Agate
- Moss Chalcedony
- Multi-inclusion Quartz
- Onyx (banded chalcedony)
- Phantom Quartz
- Prase
- Prasiolite / Green Quartz
- Quartz Cat’s-eye
- Quartz claimed to be from the Himalayas
- Quartz Crystal
- Quartz with dark needle-like inclusions
- Quartz with fine fibrous inclusions
- Quartz with flower-like inclusions
- Quartz with golden needle-like inclusions
- Quartz with green needle-like inclusions
- Quartzite Jade
- Quartzose Jade
- Red Agate
- Rock Crystal
- Rose Quartz
- Rutilated Quartz
- Sard
- Sardonyx
- Silicified Asbestos
Sub-entries (2)
- Hawk’s Eye
- Tiger’s Eye
Sub-entries (1)
- Smoky Quartz
- Smoky Quartz (brown variety)
- Strawberry Quartz
- Yellow-green Quartz
- Agate
This table scrolls sideways on narrow screens.
| Page | Content | Status |
|---|---|---|
| Browsing family | Quartz and chalcedony materials | Live |
| Treatments recorded for this material | Heated / Heat-treated (via parent material), Filled / Fracture-filled (via parent material), Dyed | Live |
| Related articles | To be added (placeholder) | Planned |
Who maintains this page
The material facts in the Onyx (banded 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; 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.