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Natural organic and biogenic materials · Organic or biogenic material · Cultured formation; treatments recorded separately

Akoya Cultured Pearl

Also known asAkoya pearl (not to be used as a name) · Japanese pearl (conditional name)

Cultured pearls from the Pinctada fucata martensii pearl oyster, with a classic white tone; all commercial Akoya pearls are cultured. Also known as Japanese pearl. 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

Care and wear

What this page can answer

This page covers

What we cannot conclude

  • Whether one particular bead is natural, treated or synthetic — only a laboratory report can settle that.
  • Geographic origin, unless an origin report accompanies the item.
  • Price, rarity or investment value: this wiki covers naming and disclosure only.

Material research: formation, causes and history

What authoritative sources say about how this material forms, what causes its colour and optical effects, where its name comes from and how people have used it. Each statement carries an evidence grade and its sources; it describes the material in general, not any specific piece.

How it forms

Layers, outside to centre:

  1. nacre
  2. bead nucleus
Schematic cross-section of Akoya Cultured Pearl, outside to centre: nacre, bead nucleus
Akoya Cultured PearlSchematic, not to scaleDrawn from the construction recorded under “Material research” on this page; assembly method not drawn (source: GIA Pearl Description · GIA Pearl Description (Chinese edition) · G&G Fall 2021 +1)If you reuse this image, please credit LumaLark Wiki and link to this pageLicense: CC BY 4.0

Akoya cultured pearls are bead cultured pearls grown in the Akoya pearl oyster, Pinctada fucata martensii. In Western markets they rank as the best-known sea-grown cultured pearl, traditionally white or cream and especially used for single-strand necklaces, and are produced in both Japan and China. Cultivation follows the general saltwater bead-culture process: a technician implants mantle tissue (saibo) together with a bead into the host, the epithelium forms a cultured pearl sac, and nacre is deposited. Note that no source dedicated to Akoya pearl formation is available here; the mechanism is given from the general saltwater bead-culture process, and mollusc-specific nacre thickness, growth duration and colour causes are not provided by the available sources.

Scope: Applies to explaining the host mollusc species, main producing areas and classic colours of Akoya cultured pearls; the pearl-forming mechanism is given according to the general procedure for beaded saltwater culturing, as sources specific to the Akoya oyster are lacking.

Sources GIA Pearl Description · GIA Pearl Description (Chinese edition) · G&G Fall 2021 +1

Where it forms

Marine farms; the host is the Akoya pearl oyster Pinctada fucata (martensii).

Sources GIA Pearl Description · GIA Pearl Description (Chinese edition) · G&G Fall 2021 +1

Japan and China are the main producing countries.

Sources GIA Pearl Description · GIA Pearl Description (Chinese edition) · G&G Fall 2021 +1

In the host mollusc's gonad, within a cultured pearl sac formed by implanted mantle epithelium.

Sources GIA Pearl Description · GIA Pearl Description (Chinese edition) · G&G Fall 2021 +1

How it forms, step by step

  1. Mantle tissue (saibo) is taken from a donor and a bead nucleus is prepared.

    Sources GIA Pearl Description · GIA Pearl Description (Chinese edition) · G&G Fall 2021 +1

  2. The bead and mantle tissue are implanted into the Akoya host oyster.

    Sources GIA Pearl Description · GIA Pearl Description (Chinese edition) · G&G Fall 2021 +1

  3. The mantle epithelium forms a cultured pearl sac and deposits nacre onto the bead.

    Sources GIA Pearl Description · GIA Pearl Description (Chinese edition) · G&G Fall 2021 +1

  4. The classically white or cream Akoya cultured pearl forms (mechanism from the general saltwater bead-culture process; no Akoya-specific source).

    Sources GIA Pearl Description · GIA Pearl Description (Chinese edition) · G&G Fall 2021 +1

Link to appearance

Akoya cultured pearls are classically white or cream and are widely used for single-strand necklaces; the colour description comes from the GIA encyclopedia, which gives no causal mechanism.

Sources CIBJO Pearl Book 2024 · G&G Fall 2021 · GIA Pearl Description (Chinese edition) +1

Timescale

The available sources give no nacre-thickness or growth-duration data for Akoya cultured pearls.

Sources GIA Pearl Description

Related base materials

  • Cultured pearl: cultured-pearl-type-by-mollusc | Cultured pearl category defined by the host mollusc (the Akoya pearl oyster, Pinctada fucata martensii)

Supporting findings

Akoya cultured pearls are produced in Japan as well as China.

Evidence grade A

Scope: Origin overview; no specific regions or production statistics.

Sources GIA Pearl Description · GIA Pearl Description (Chinese edition)

The formation mechanism of Akoya cultured pearls follows the general saltwater bead-culture process (implanting a bead and mantle tissue); lacking an Akoya-specific source, this is inferred by analogy and carries lower evidence strength.

Evidence grade C

Scope: No Akoya-specific source; the mechanism is inferred from the general saltwater culture process of other Pinctada species.

Sources G&G Fall 2021 · G&G Spring 2013

Recorded localities

This is an organic material; its localities are the harvest or culture areas (waters or species ranges) recorded by authoritative sources.

Locality sketch mapLand outlines only; the map does not depict any national or regional boundary. Dots mark approximate positions. Base map: Natural Earth (public domain).

Asia

  • JapanOrganic harvest or culture area
    Sources CIBJO Pearl Book 2024 · GIA Pearl Description
  • ChinaOrganic harvest or culture area
    Sources CIBJO Pearl Book 2024 · GIA Pearl Description

Oceania

These are localities recorded by authoritative sources, not an origin finding for any individual piece. The CIBJO Gemstone Book (2022, §4.2.3) says a place of origin names where a gem was mined or harvested, is a matter of opinion, does not imply a level of quality, and that cutting, processing or exporting centres must not be used to imply origin. See how far testing can go on this page, the origin determination guide and the overview of recorded localities.

How it is identified

Akoya cultured pearls are often treated to enhance appearance, and they can resemble natural pearls, other cultured pearls, and imitations, so the eye cannot tell whether they are cultured or treated. Determination relies on laboratory testing such as real-time X-radiography, real-time microradiography for nacre thickness, UV-visible reflectance spectroscopy, X-ray fluorescence, and computed micro-tomography (μCT). Pearl category and any detectable treatment must be judged by an accredited laboratory, and this entry provides no self-test threshold.

Evidence grade A

Scope: Appearance is insufficient to decide cultured or treated status; determination requires testing by an accredited laboratory, and this entry gives no self-test threshold.

Sources GIA: How GIA Identifies Pearls · CIBJO Pearl Book 2024

Other research findings

The Akoya pearl oyster — Pinctada fucata (martensii) — serves as host for Akoya cultured pearls.

Evidence grade A

Scope: The mollusc's scientific name is supported by GIA sources; there is no Akoya-specific formation source.

Sources CIBJO Pearl Book 2024 · G&G Fall 2021 · GIA Pearl Description (Chinese edition) +1

Akoya cultured pearls are the most familiar saltwater cultured pearl in Western markets, classically white or cream, widely used for single-strand necklaces.

Evidence grade A

Scope: Market/appearance description, not a formation or composition claim.

Sources GIA Pearl Description · GIA Pearl Description (Chinese edition)

Pearl quality is usually assessed through lustre, nacre thickness, surface, shape, colour and matching (GIA summarises the pearl value factors as seven: size, shape, colour, nacre, lustre, surface and matching). Akoya cultured pearls are known for a sharp, bright mirror-like lustre and have relatively thin nacre, so nacre thickness and durability draw particular attention in evaluation. The market generally prizes a bright interference-colour lustre, a clean surface, a round shape, and close matching of size and colour (often with pink, gold or green overtones) within a strand. Category and any treatment must be determined by an accredited laboratory through testing.

Evidence grade A

Scope: This describes the pearl quality characteristics the market generally prizes; it is not a grade for any specific specimen and is neither price nor investment advice; pearl category (natural or cultured) and any treatment must be determined by an accredited laboratory on the specific specimen.

Sources GIA: How GIA Identifies Pearls · CIBJO Pearl Book 2024

Limits of this research

  • Research status: Formation, occurrence or other material-specific findings found in authoritative sources
  • No Akoya-specific formation source: the mechanism is inferred from the general saltwater bead-culture process and marked C.
  • No nacre-thickness, growth-duration or colour-cause data for Akoya pearls; none borrowed from other molluscs.
  • The white/cream description comes from the GIA encyclopedia, which gives no causal mechanism.
  • CIBJO Pearl Book 2024 (5.6) defines an Akoya cultured pearl only as a beaded cultured pearl produced in Pinctada fucata (martensii); it does not cover the formation mechanism.

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
Akoya Cultured Pearl

16 CFR Part 23 §23.20(b), §23.26(a)

Construction or treatment status

Cultured formation; treatments recorded separately

Treatments recorded for this material: Bleached (via parent material), Dyed (via parent material), Irradiated (via parent material)

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

Akoya Cultured Pearl is Cultured pearl from the Pinctada fucata martensii oyster; classic white pearl; use "Akoya Cultured Pearl" for listings, and disclose any known treatments.

Evidence

What this means for you

Before buying, check the recommended listing name "Akoya Cultured Pearl" 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

The normal and special care that applies to all natural and cultured pearls, and so to Akoya Cultured Pearl (CIBJO Pearl Book §7.1, §7.2; the source says this advice counts as normal across the whole range and should be passed on to the buyer), is set out in full under care on the Pearl entry.

Care

Akoya Cultured Pearl — care (light): may fade or revert to its original colour, so it should not be left for long periods in strong natural or artificial light or under strong display lighting.

CIBJO Pearl Book 2024

Treatment state
treated
Only after these treatments
coating, dyeing
Source & check 2026-09-26
Source
  • CIBJO Blue Book — Pearl Book (Pearl Commission 2024-1) (CIBJO): §8.2 Annex C, Akoya Cultured Pearl, p.54; §7.2, §7.2.2 (locator checked 2026-09-26)
Fact checked on
2026-09-26

Akoya Cultured Pearl — care (wear): breaks easily, so it is not meant for everyday wear and should not be worn during heavy work.

CIBJO Pearl Book 2024

Treatment state
treated
Only after these treatments
filling
Source & check 2026-09-26
Source
  • CIBJO Blue Book — Pearl Book (Pearl Commission 2024-1) (CIBJO): §8.2 Annex C, Akoya Cultured Pearl, p.54; §7.2, §7.2.1 (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.

Common care questions and matching entries

WearCare and wear for Akoya Cultured Pearl can be registered against the Pearl Book of the CIBJO Blue Book (Pearl Commission 2024-1). LightTreated Akoya cultured pearls, and only those that are coated or dyed, may fade or revert to their original colour and should not be left for long periods in strong natural light, strong artificial light or strong display lighting. WearTreated Akoya cultured pearls, and only those that are filled, break easily, are not meant for everyday wear and should not be worn during heavy physical work. The general and specific care advice in the CIBJO Pearl Book should be treated as standard for all pearls and passed on to the buyer; it is listed in full in the care part of the Pearl entry.

This table scrolls sideways on narrow screens.

QuestionMatching entries
Light and displaymay fade or revert to its original colour, so it should not be left for long periods in strong natural or artificial light or under strong display lighting
Wearing limits (knocks, settings)breaks easily, so it is not meant for everyday wear and should not be worn during heavy work

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.

treated (Only after these treatments: coating, dyeing)

treated (Only after these treatments: filling)

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
Bleaching——Optimization——
Dyeing——Treatment——
Irradiation——Treatment——

“—” means the cited source gives no value for that item, not “none”. Source: GB/T 16552—2017 Table B.1 (row for Cultured Pearl)

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

For Akoya Cultured Pearl, "Japanese pearl" is recorded with no restriction on use as a name, while "Akoya pearl" must not be used as a name (CIBJO Pearl Book 2024 §4.4.1.1.2; CIBJO Pearl Book 2024 §5.6; 16 CFR Part 23 §23.26(a)); 4 further names in non-Latin scripts are listed in the name register below (3 with no restriction recorded on use as a name, 1 that may appear only as an annotation, never as the product name).

Standard and listing namesThe GB/T 16552—2017 naming counterpart for Akoya Cultured Pearl is “Saltwater Cultured Pearl” (Table A.3, row “Saltwater cultured pearl (seawater pearl)”); this name itself is not in the standard. The suggested listing name is Akoya Cultured Pearl. Names in four languagesThe four-language names are given in Simplified Chinese, Traditional Chinese, English (Akoya Cultured Pearl) and Japanese, the Japanese being the GSJ (Japan) formal name. Institution usageAmong authority wordings, CIBJO lists Akoya Cultured Pearl, with a qualifying note separated from the title name (CIBJO Pearl Book); the FTC text on file has no wording for this name (checked), and GIA and Gem-A have not been checked; bodies without a recorded wording show the entry's own English name, which does not represent their position. National standard namesGermany (RAL) writes Akoya-Zuchtperle and the EU writes Akoya Cultured Pearl. Trade and mineralogical namesTrade names and synonyms also include Akoya pearl, Japanese pearl, a mixed Latin-Chinese form of the Akoya cultured pearl name, and the Chinese trade name for “Tennyo” pearl. Candidate search termsOf these, Akoya pearl is not an acceptable name, Japanese pearl is only a candidate search term, and the Tennyo pearl name may only be added as a note, never as the main product name, because “Tennyo” is a quality title given by a testing laboratory, not a type of material.

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 (4)
Japanese pearlEnglishmarket namesearch candidate onlyno restriction recordededitorial ruling (no clause cited); Note: Related high-risk name “Pearl”.
Akoya养殖珍珠Simplified Chinesemarket namematched automaticallyno restriction recordededitorial ruling (no clause cited)
马氏珠母贝产有核珍珠Simplified Chinesenarrower name (variety or subtype)matched automaticallyno restriction recordedGB/T 18781—2023 A; GB/T 18781—2023 3.2.1
马氏珠母贝海水珍珠Simplified Chinesenarrower name (variety or subtype)matched automaticallyno restriction recordedGB/T 18781—2023 3.2.1
annotation only, never as the product name (1)
天女珍珠Simplified Chinesemarket namematched only once the condition is confirmedannotation only, never as the product nameCIBJO Pearl Book 2024 4.4.1.1.2; GB/T 16552—2017 5.1.2.3 b); GB/T 16552—2017 5.1.1 c); Note: Related high-risk name “Australian white, Tennyo, Aurora, Baroque”: “Tennyo” is a laboratory quality designation, not a material; the material is still Akoya cultured pearl.
not to be used as a name (1)
Akoya pearlEnglishmarket namematched automaticallynot to be used as a nameCIBJO Pearl Book 2024 4.4.1.1.2; CIBJO Pearl Book 2024 §5.6; 16 CFR Part 23 §23.26(a); Note: Related high-risk name “Pearl”.

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

Authority wording

GIA, FTC, CIBJO, Gem-A
Akoya Cultured Pearl (on record for CIBJO; 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
アコヤ養殖真珠
GB/T naming counterpart (this name is not in the standard)
海水养殖珍珠 (GB/T 16552—2017 Table A.3, row “Saltwater Cultured Pearl”)
Mineralogical name
Cultured pearl from the Pinctada fucata martensii oyster; classic white pearl
Trade names and synonyms
Japanese pearl (market name; conditional name)Not to be used as a name: Akoya pearl (market name)

Four-language names

简体中文
阿古屋养殖珍珠
繁體中文
阿古屋養殖珍珠
English
Akoya Cultured Pearl
日本語
アコヤ養殖真珠

National and regional formal names

Germany (RAL)
Akoya-Zuchtperle
European Union
Akoya Cultured Pearl

Qualifiers stripped from the headline name

  • CIBJO: (CIBJO Pearl Book)

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

Classification

Origin
Natural materials
Material domain
Natural organic and biogenic materials
Browsing family
Pearl and molluscan shell materials
Identity tier
Organic or biogenic material
Mineral chemical class
Not applicable
Construction or treatment status
Cultured formation; treatments recorded separately

Treatments listed by standards

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

Under the “Cultured Pearl (Pearl)” row of Table B.1: Bleaching Optimization; Dyeing Treatment; Irradiation Treatment. The full row, with the effect column, is on the Cultured Pearl 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.

What it is and how it's identified

Akoya Cultured Pearl is a beaded cultured pearl produced in the Akoya pearl oyster Pinctada fucata (also known as martensii); this is a CIBJO trade definition from an institutional handbook, not a national standard. All other values are taken at the level of the class named in the cited clause, not measured separately. For cultured pearls (the whole class): the inorganic part of the structure is a radially arranged aggregate, with aragonite orthorhombic and calcite trigonal, and the organic part is amorphous; Mohs hardness is 2.5–4; cleavage is usually not seen in the aggregate; the optic character is that of an aggregate and birefringence cannot be measured on the aggregate; when untreated, the lustre is pearly, and it effervesces on contact with acid. The density of 2.72–2.78 g/cm³ is taken for saltwater cultured pearls (the whole class); the refractive index of 1.53–1.68 is taken for cultured pearls (the whole class) and is a spot-method reading, a typical value rather than an absolute limit; the clause has further sub-grades, and the overall value is used.

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”.

Luminescence, UV-visible spectrum, infrared spectrum, magnification: these whole-class features are given in the cited clause for cultured pearl (the whole class), so they are not repeated on the Akoya Cultured Pearl page; see the material facts on the Cultured Pearl entry.

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

Definition

Akoya Cultured Pearl: a beaded cultured pearl produced in Pinctada fucata (martensii) (9.54), the Akoya pearl oyster.

CIBJO Pearl Book 2024

Qualification

CIBJO trade definition from an institutional manual, not a national standard.

Source & check 2026-09-25
Source
  • CIBJO Blue Book — Pearl Book (Pearl Commission 2024-1) (CIBJO): §5.6, p.22 (locator checked 2026-09-25)
Fact checked on
2026-09-25

Structure

Akoya Cultured Pearl — structure (overall): inorganic part: aragonite (orthorhombic) and calcite (trigonal) in radiating aggregates; organic part: amorphous.

GB/T 16553—2017

Does this standard apply
applies to this entry
What this covers
cultured pearl (the whole class)
Source & check 2026-09-26
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.3.2 (locator checked 2026-09-26)
Fact checked on
2026-09-26

Durability

Akoya Cultured Pearl — Mohs hardness: 2.5–4

GB/T 16553—2017

123456789102.5–4References (diamond = value, bar = range; below)

Reference points on this site: Talc 1–3, Fluorite 4, Apatite 5–5.5, Orthoclase 6–6.5, Topaz 8, Diamond 10 (Source: GB/T 16553—2017); Gypsum 1.5–2, Calcite 3, Quartz 7 (Source: Handbook of Mineralogy); Corundum 9 (Source: GIA Gem Encyclopedia (care guide))

Mohs hardnessSource: GB/T 16553—2017
Does this standard apply
applies to this entry
What this covers
cultured pearl (the whole class)
Source & check 2026-09-26
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.3.2 (locator checked 2026-09-26)
Fact checked on
2026-09-26

Akoya Cultured Pearl — cleavage: generally not seen on an aggregate

GB/T 16553—2017

Does this standard apply
applies to this entry
What this covers
cultured pearl (the whole class)
Source & check 2026-09-26
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.3.2 (locator checked 2026-09-26)
Fact checked on
2026-09-26

Akoya Cultured Pearl — stability: effervesces in acid

GB/T 16553—2017

Treatment state
untreated
Does this standard apply
applies to this entry
What this covers
cultured pearl (the whole class)
Source & check 2026-09-26
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.3.2 (locator checked 2026-09-26)
Fact checked on
2026-09-26

Physical properties

Akoya Cultured Pearl — density: 2.72–2.78 g/cm³

GB/T 16553—2017

0.51.52.53.54.55.56.57.52.72–2.78
Specific gravitySource: GB/T 16553—2017
Does this standard apply
applies to this entry
What this covers
saltwater cultured pearl (the whole class)
Source & check 2026-09-26
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.3.2 Density · Saltwater cultured pearl (locator checked 2026-09-28)
Fact checked on
2026-09-26

Akoya Cultured Pearl — feel (texture): feels gritty when two surfaces are rubbed together

GB/T 16553—2017

Does this standard apply
applies to this entry
What this covers
cultured pearl (the whole class)
Source & check 2026-09-26
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.3.2 (locator checked 2026-09-26)
Fact checked on
2026-09-26

Optical

Akoya Cultured Pearl — optic character: aggregate

GB/T 16553—2017

Does this standard apply
applies to this entry
What this covers
cultured pearl (the whole class)
Source & check 2026-09-26
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.3.2 (locator checked 2026-09-26)
Fact checked on
2026-09-26

Akoya Cultured Pearl — refractive index: 1.53–1.68

GB/T 16553—2017

1.31.72.12.52.93.31.53–1.68
Refractive indexSource: GB/T 16553—2017
Does this standard apply
applies to this entry
What this covers
cultured pearl (the whole class)
Qualification

The clause we cite gives this as a value read by the spot (distant-vision) method. It is a common value, not an absolute limit.

General note
the clause has finer ranges
Source & check 2026-09-26
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.3.2 (locator checked 2026-09-26)
Fact checked on
2026-09-26

Akoya Cultured Pearl — birefringence: not measurable on an aggregate

GB/T 16553—2017

Does this standard apply
applies to this entry
What this covers
cultured pearl (the whole class)
Source & check 2026-09-26
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.3.2 (locator checked 2026-09-26)
Fact checked on
2026-09-26

Akoya Cultured Pearl — pleochroism: not measurable on an aggregate

GB/T 16553—2017

Treatment state
untreated
Does this standard apply
applies to this entry
What this covers
cultured pearl (the whole class)
Source & check 2026-09-26
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.3.2 (locator checked 2026-09-26)
Fact checked on
2026-09-26

Quality factors

Akoya Cultured Pearl — quality factor (lustre): pearly

GB/T 16553—2017

Treatment state
untreated
Does this standard apply
applies to this entry
What this covers
cultured pearl (the whole class)
Source & check 2026-09-26
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.3.2 (locator checked 2026-09-26)
Fact checked on
2026-09-26

Akoya Cultured Pearl — quality factor (nacre thickness): extra thick (A) ≥0.6 mm; very thick (B) ≥0.5 mm; thick (C) ≥0.4 mm; medium (D) ≥0.3 mm; thin (E) <0.3 mm.

GB/T 18781—2023

A extra thick≥0.6 mmB very thick≥0.5 and <0.6 mmC thick≥0.4 and <0.5 mmD medium≥0.3 and <0.4 mmE thin<0.3 mm
Nacre thickness gradesSource: GB/T 18781—2023
Treatment state
untreated
Does this standard apply
applies to this entry
Measurement condition
GB/T 18781—2023 §6.6: direct measurement (arbitration method), X-ray method or optical coherence tomography; nacre thickness in mm to one decimal place
Nucleation
beaded
Qualification

GB/T 18781—2023 names this scale for beaded cultured pearls from the Pinctada fucata martensii oyster (named by its Chinese species name in the standard); such pearls are graded in millimetres by this table instead of by the PT% ratio of Table 4. Each bound is a lower limit only (≥); the standard gives no upper limits.

Source & check 2026-09-26
Source
  • GB/T 18781—2023 Cultured pearl grading (GB/T): §4.6.2, Annex A (normative) Table A.1, §6.6 (locator checked 2026-09-26)
Fact checked on
2026-09-26

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

1.581.61.622.62.72.82.93Refractive indexSpecific gravity12345Akoya Cultured Pearl

This material (RI / SG midpoints): 1.605 / 2.75; Closest values: 1Larimar 1.62 / 2.82, 2Natural Conch Pearl / Natural Melo Pearl 1.595 / 2.84, 3Aquamarine 1.58 / 2.79, 4Turquoise 1.63 / 2.65, 5Prehnite 1.625 / 2.88

Show the full chart (330 registered materials)1.41.51.61.71.81.922.12.22.32.41234567Refractive indexSpecific gravity12345Akoya Cultured Pearl

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)

Related CIBJO terms

Sango cultured pearl

a trade name for a pink atypical bead cultured pearl produced in Japan within Pinctada fucata that uses a pink coral bead as the substrate for nacre growth.

CIBJO Blue Book — Pearl Book (Pearl Commission 2024-1) (CIBJO): §5.175, p.42

Entries in the source that only point to another clause: Akoya (§5.5, p.22) → §9.3, §9.54

Definitions are quoted verbatim from the cited CIBJO Blue Book; […] marks an excerpt, and the full definition is at the cited clause.

Pearl-producing molluscs (CIBJO Annex D): §9.3 Akoya pearl oyster · §9.4 Akoya complex · §9.9 Australian akoya pearl oyster · §9.54 Pinctada fucata · §9.57 Pinctada martensii

Testing and market

The CIBJO laboratory protocol covers Akoya Cultured Pearl under “Pearl” (§6.2.17): see identification on the Pearl entry; the required tests are listed on the CIBJO laboratory protocol table for Pearl.

How far testing can go

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

16 CFR Part 23
Naming rule §23.20(b) · Source
16 CFR Part 23
Naming rule §23.26(a) · 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 Pearl on this site: 17 entries listed by this site's parent-entry links; synthetic, treated and similar entries carry their recorded state after the name; this page (Akoya Cultured Pearl) is marked.

This table scrolls sideways on narrow screens.

PageContentStatus
Browsing familyPearl and molluscan shell materialsLive
Treatments recorded for this materialBleached (via parent material), Dyed (via parent material), Irradiated (via parent material)Live
Related articlesTo be added (placeholder)Planned

Who maintains this page

The material facts in the Akoya Cultured Pearl 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 2026-09-25 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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