On this page
UnderstandWhat it is, what people ask, how far this page goes
Natural organic and biogenic materials · Organic or biogenic material · Natural identity; treatment status unknown
Freshwater Natural Pearl
Also known asFreshwater pearl (conditional name) · Scottish pearls (annotation only, never as the product name)
A pearl formed naturally in a freshwater mollusc without human intervention; GB/T 16552-2017 requires keeping the word "natural". Also known as Freshwater 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.
What this page can answer
This page covers
- How Freshwater Natural Pearl forms and what gives its colourFormation setting, process and timescale, each finding graded and sourced
- How to identify Freshwater Natural PearlIdentification points from the research literature; how far lab testing can go
- Treatments and enhancements of Freshwater Natural PearlThe enhancements and treatments the GB/T and JJA/AGL tables list
- Caring for and wearing Freshwater Natural PearlCleaning, heat, chemicals and light, as the cited sources give them
- Hardness, density and refractive index of Freshwater Natural PearlEach value with its source and check date
- Freshwater Natural Pearl in English, Chinese and Japanese; national standard namesNames in four languages, the GB/T standard name and the suggested listing name; and: Has any of GIA, FTC, CIBJO or Gem-A put a name for it on record here?
- Listing and disclosing Freshwater Natural PearlThe listing name to use; what must be disclosed before sale
- Standard clauses that define Freshwater Natural PearlWhich 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
A natural freshwater pearl forms inside a freshwater mollusc—such as the Unio mussel of North American rivers and lakes—around a microscopic irritant, entirely without human intervention. It shares the general natural-pearl mechanism: mantle epithelium envelops the irritant to form a pearl sac, which secretes nacre (aragonite plus organic matrix) in layers. The distinction from freshwater cultured pearls is human intervention: culturing implants pieces of mantle tissue to induce pearl sacs, whereas a natural freshwater pearl relies on the mollusc alone. American freshwater pearls derive their distinctive shapes and colours from the Unio in which they grow.
Scope: Applies to explaining natural pearls produced by freshwater molluscs and formed without human intervention; does not apply to freshwater cultured pearls or imitation pearls.
Sources GIA Pearl Description · GIA Pearl Description (Chinese edition) · G&G Fall 1984 +1
Where it forms
Freshwater environments, namely rivers and lakes; North American natural freshwater pearls have the Unio mussel as their source.
Sources GIA Pearl Description · GIA Pearl Description (Chinese edition) · G&G Fall 1984
In the body or mantle tissue of freshwater molluscs.
Sources GIA Pearl Description · GIA Pearl Description (Chinese edition) · G&G Fall 1984
How it forms, step by step
An irritant lodges in the body or mantle tissue of the freshwater mollusc.
Sources GIA Pearl Description · GIA Pearl Description (Chinese edition) · G&G Fall 1984
Mantle epithelium proliferates and envelops the irritant, forming a natural pearl sac.
Sources GIA Pearl Description · GIA Pearl Description (Chinese edition) · G&G Fall 1984
The pearl sac continuously secretes nacre (aragonite plus organic matrix), which builds up in layers.
Sources GIA Pearl Description · GIA Pearl Description (Chinese edition) · G&G Fall 1984
The nacre thickens into a natural freshwater pearl whose shape and colour reflect the host mussel (e.g., Unio).
Sources GIA Pearl Description · GIA Pearl Description (Chinese edition) · G&G Fall 1984
Link to appearance
The shape and colour of a natural freshwater pearl depend on the host mussel (e.g., Unio), giving a distinctive, non-standardised appearance.
Sources GIA Pearl Description · GIA Pearl Description (Chinese edition) · CIBJO Pearl Book 2024
Timescale
The available authoritative sources give no growth duration or absolute age for natural freshwater pearls.
Sources GIA Pearl Description · GIA Pearl Description (Chinese edition) · G&G Fall 1984
Related base materials
- Natural pearl: subtype-by-environment | A subtype of natural pearl classified by growth environment; the host is a freshwater mollusc (such as Unio mussels)
Supporting findings
Within certain mollusks, natural pearls develop either in the body or in the mantle tissue. As a rule a microscopic irritant is the point around which they grow, and no human intervention whatever is involved.
Evidence grade AScope: General definition of natural pearls; used here to frame natural freshwater pearls without a freshwater-specific mechanism.
Sources GIA Pearl Description · GIA Pearl Description (Chinese edition)
The Unio mussel is the source of American natural freshwater pearls, and it is obtained from the rivers and lakes of the American continent.
Evidence grade BScope: Single historical article (1984) summary covering American freshwater pearls; not representative of all localities.
Sources G&G Fall 1984
Recorded localities
This is an organic material; its localities are the harvest or culture areas (waters or species ranges) recorded by authoritative sources.
Africa
- EgyptCIBJO: ancient times
Sources CIBJO Pearl Book 2024
- CIBJO Blue Book — Pearl Book (Pearl Commission 2024-1)
Asia
- Bangladesh
Sources CIBJO Pearl Book 2024
- CIBJO Blue Book — Pearl Book (Pearl Commission 2024-1)
Europe
- United Kingdomprinted as Great Britain; CIBJO: historical (freshwater pearl mussel)
Sources CIBJO Pearl Book 2024
- CIBJO Blue Book — Pearl Book (Pearl Commission 2024-1)
- Scotland, United KingdomCIBJO: historical (freshwater pearl mussel)
Sources CIBJO Pearl Book 2024
- CIBJO Blue Book — Pearl Book (Pearl Commission 2024-1)
- AustriaCIBJO: historical (freshwater pearl mussel)
Sources CIBJO Pearl Book 2024
- CIBJO Blue Book — Pearl Book (Pearl Commission 2024-1)
- Czechiaprinted as Czechoslovakia; CIBJO: historical (freshwater pearl mussel)
Sources CIBJO Pearl Book 2024
- CIBJO Blue Book — Pearl Book (Pearl Commission 2024-1)
- DenmarkCIBJO: historical (freshwater pearl mussel)
Sources CIBJO Pearl Book 2024
- CIBJO Blue Book — Pearl Book (Pearl Commission 2024-1)
- FranceCIBJO: historical (freshwater pearl mussel)
Sources CIBJO Pearl Book 2024
- CIBJO Blue Book — Pearl Book (Pearl Commission 2024-1)
- GermanyCIBJO: historical (freshwater pearl mussel)
Sources CIBJO Pearl Book 2024
- CIBJO Blue Book — Pearl Book (Pearl Commission 2024-1)
- NorwayCIBJO: historical (freshwater pearl mussel)
Sources CIBJO Pearl Book 2024
- CIBJO Blue Book — Pearl Book (Pearl Commission 2024-1)
- RussiaCIBJO: historical (freshwater pearl mussel)
Sources CIBJO Pearl Book 2024
- CIBJO Blue Book — Pearl Book (Pearl Commission 2024-1)
North America
- United StatesCIBJO lists several U.S. mussels; G&G (1984) says the U.S. industry still produces
Sources CIBJO Pearl Book 2024 · G&G Fall 1984
- CIBJO Blue Book — Pearl Book (Pearl Commission 2024-1)
- Freshwater Pearls of North America (Gems & Gemology, Fall 1984, Vol. 20, No. 3)
- Ohio River system, United Stateshistorical (CIBJO: Historic/Historical)
Sources CIBJO Pearl Book 2024
- CIBJO Blue Book — Pearl Book (Pearl Commission 2024-1)
- Notch Brook, New Jersey, United States1857 "rediscovery" that began the U.S. pearl fisheries
Sources G&G Fall 1984
- Little Miami River, Ohio, United States
Sources G&G Fall 1984
- Pecatonica and other rivers, Wisconsin, United States
Sources G&G Fall 1984
- White River, Arkansas, United States
Sources G&G Fall 1984
- Clinch River, Tennessee, United States
Sources G&G Fall 1984
- Lower Mississippi River, United StatesG&G: early finds, minor in scope
Sources G&G Fall 1984
- Newfoundland, Canada
Sources CIBJO Pearl Book 2024
- CIBJO Blue Book — Pearl Book (Pearl Commission 2024-1)
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
A natural freshwater pearl is not reliably separable from cultured or imitation pearls by sight. A laboratory uses routine gemological tests along with UV-Vis reflectance spectroscopy, X-ray fluorescence and real-time X-radiography, measuring nacre thickness as needed, to assess natural freshwater origin; the call must come from an accredited body.
Evidence grade AScope: Determining natural freshwater origin falls under laboratory testing and must be concluded by an accredited body.
Sources GIA: How GIA Identifies Pearls
Other research findings
Natural freshwater pearls are distinguished from freshwater cultured pearls by human intervention—culturing implants mantle tissue.
Evidence grade AScope: Conceptual natural-vs-cultured boundary; not a per-sample identification.
Sources GIA Pearl Description · GIA Pearl Description (Chinese edition)
American freshwater pearls derive their distinctive shapes and colours from the Unio in which they grow.
Evidence grade BScope: From a single historical source on American freshwater pearls; scope limited to that provenance.
Sources G&G Fall 1984
By CIBJO's definition, a freshwater natural pearl arises from a bivalve mollusc whose habitat is freshwater.
Evidence grade AScope: The naming definition (clause 5.78); defines the freshwater category of natural pearls by its bivalve host.
Sources CIBJO Pearl Book 2024
Natural freshwater pearls are described by lustre, surface, shape, colour and matching. A natural pearl has no bead and is nacre throughout, so the 'nacre thickness' measure does not apply; assessment emphasises lustre, surface, shape and consistency of matching. The emphasis differs from that for freshwater cultured pearls, and telling them apart requires laboratory testing. Imitation pearls are not subject to pearl quality assessment.
Evidence grade AScope: Quality factors describe which characteristics the market generally prizes; they are not a grade for any specific specimen and are neither price nor investment advice. Pearl quality assessment must be issued by an accredited laboratory for a specific specimen.
Sources CIBJO Pearl Book 2024 · GIA: How GIA Identifies Pearls
Limits of this research
- Research status: Formation, occurrence or other material-specific findings found in authoritative sources
- No source specifically dedicated to natural freshwater pearl formation was available before; the CIBJO Pearl Book 2024 clause 5.78 now provides the naming definition, while formation detail still relies on the general natural-pearl definition plus a 1984 historical article.
- No growth duration or age data.
- Only the 1984 article's abstract was available, without the full formation discussion.
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
- Freshwater Natural Pearl (confirmed by report)
GB/T 16552—2017 Table A.3 “Freshwater Natural Pearl” · CIBJO Pearl Book 2024 §5.78
Construction or treatment status
Natural identity; treatment status unknown
Treatments recorded for this material: Bleached (via parent material), Dyed (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
"Freshwater Natural Pearl" is a market name rather than a mineral species name; before using it, verify: Laboratory identification required before the name is used.
Evidence
- GB/T · Table A.3, row 天然淡水珍珠 (Freshwater Natural Pearl)
What this means for you
Before buying, check the recommended listing name "Freshwater Natural Pearl (confirmed by report)" and any disclosed treatments on this page, and ask the seller for a grading report if in doubt.
Known uncertainty
- This entry's exact material identity is not fully settled.
- See “Disclosure and cautions” above
- Last reviewed
- 2026-09-01
Trade-name ruling
- Laboratory identification required before the name is used.
- Suggested listing name
- Freshwater Natural Pearl (confirmed by report)
Care and wear
The normal and special care that applies to all natural and cultured pearls, and so to Freshwater Natural 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
Freshwater Natural 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
- dyeing
Source & check 2026-09-26
- Source
- CIBJO Blue Book — Pearl Book (Pearl Commission 2024-1) (CIBJO): §8.1 Annex C, Freshwater Pearl, p.51; §7.2, §7.2.2 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Each row's “Source & check” expands to the full source; the date beside it is the fact check date.
Common care questions and matching entries
The general and specific care for all natural and cultured pearls also applies to Freshwater Natural Pearl; the CIBJO Pearl Book (Pearl Book 2024-1) states that this advice should be treated as standard for all pearls and passed on to the buyer, and it is listed in full in the care part of the Pearl entry. Light and displayOn light and display, the CIBJO Pearl Book (Pearl Book 2024-1) states that Freshwater Natural Pearl may fade or revert to its original colour and should not be left for long periods in strong natural light, strong artificial light or strong display lighting; this applies to treated freshwater natural pearls, and only those that have been dyed.
This table scrolls sideways on narrow screens.
| Question | Matching entries |
|---|---|
| Light and display | 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 |
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 |
|---|---|---|---|---|---|
| Bleaching | — | — | Optimization | — | — |
| Dyeing | — | — | Treatment | — | — |
“—” means the cited source gives no value for that item, not “none”. Source: GB/T 16552—2017 Table B.1 (row for Natural 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
How lab reports word it
Report wording for Freshwater Natural Pearl is set out under report wording on the Pearl entry.
VerifyNames, standards, technical facts, clauses and sources
Names
For Freshwater Natural Pearl, "Freshwater pearl" is recorded with no restriction on use as a name, while "Scottish pearls" may appear only as an annotation, never as the product name (CIBJO Pearl Book 2024 §5.178 “Scottish pearls”; GB/T 16552—2017 §5.1.2.3 c); GB/T 16552—2017 §5.1.1 c)).
Chinese standard nameThe GB/T 16552—2017 formal name for Freshwater Natural Pearl is natural freshwater pearl (Table A.3). Trade and mineralogical namesA common trade name is Freshwater pearl, of conditional use. Candidate search termsScottish pearls is an older name, kept only as a candidate search term, which may appear only as a note and must not be used as the main product name. Recommended listing nameThe suggested listing name is Freshwater Natural Pearl (confirmed by certificate). Names in four languagesFour-language names are given in Simplified Chinese, Traditional Chinese, English (Freshwater Natural Pearl) and Japanese; the Japanese form is the entry's own, and the wording of Japan's GSJ for this name is not yet verified by this site. Institution usageOn authority wording, the FTC text on file has no wording for this name (checked), and GIA, CIBJO and Gem-A are unchecked; bodies without a recorded wording show the entry's own English name, which does not represent their position. Trade and mineralogical namesThe mineralogical name means a natural pearl formed in a freshwater mollusc.
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 (1) | ||||
| Freshwater pearlEnglish | market name | matched only once the condition is confirmed | no restriction recorded | CIBJO Pearl Book 2024 Annex C §8.1 “Freshwater Pearl”; CIBJO Pearl Book 2024 4.4.1.1.2; GB/T 16552—2017 5.1.2.3 b); GB/T 16552 revision draft for comment (2023, not in force) Table A.3 |
| annotation only, never as the product name (1) | ||||
| Scottish pearlsEnglish | historical name | search candidate only | annotation only, never as the product name | CIBJO Pearl Book 2024 §5.178 “Scottish pearls”; GB/T 16552—2017 5.1.2.3 c); GB/T 16552—2017 5.1.1 c) |
How each authority words this name: see Names › Authority wording.
- GSJ (Japan) formal name
- 天然淡水真珠 (not yet checked for this body — the entry's own Japanese name is shown)
- Chinese formal name
- 天然淡水珍珠 (GB/T 16552—2017 Table A.3)
- Mineralogical name
- Natural pearl formed in a freshwater mollusc
- Trade names and synonyms
- Scottish pearls (historical name; annotation only, never as the product name) · Freshwater pearl (market name; conditional name)
Four-language names
- 简体中文
- 天然淡水珍珠
- 繁體中文
- 天然淡水珍珠
- English
- Freshwater Natural Pearl
- 日本語
- 天然淡水真珠
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
- Natural identity; treatment status unknown
Treatments listed by standards
For Freshwater Natural Pearl, this site applies the "Natural Pearl" row of GB/T 16552—2017 Annex B, Table B.1: bleaching is categorised as an optimization and dyeing as a treatment. The full row with the effect column is on the Natural Pearl page; what Table B.1 is, and how its grades are defined, are on the Gem treatments page.
GB/T 16552-2017, Annex B, Table B.1
Under the “Natural Pearl” row of Table B.1: Bleaching Optimization; Dyeing Treatment. The full row, with the effect column, is on the Natural 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
The chemical composition and density of Freshwater Natural Pearl are registered for freshwater natural pearl itself, while structure, hardness, cleavage, optic character, refractive index, birefringence and lustre take values for natural pearl (the whole class). Freshwater Natural Pearl is relatively rich in trace elements such as Mn and relatively poor in Sr, S, Na, Mg and others; density 2.66–2.78 g/cm³, and the cited clause adds that values above 2.74 are rare. Also registered for natural pearl as a whole class: the inorganic part is a radially arranged aggregate; Mohs hardness 2.5–4.5; cleavage usually not seen in an aggregate; optic character aggregate; refractive index 1.53–1.68, which the cited clause gives as a spot-method reading, a common value rather than an absolute limit, the clause having finer sub-ranges and the register taking the overall value; birefringence not measurable for an aggregate; untreated, the quality factor is pearly lustre. The GIA Gem Encyclopedia gives a Mohs hardness of 2.5–3; the cited clause covers the whole species, of which Freshwater Natural Pearl is only one variety.
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 natural pearl (the whole class), so they are not repeated on the Freshwater Natural Pearl page; see the material facts on the Natural Pearl entry.
Items below that name the class they cover give the cited clause’s value for that whole class, not a measurement of Freshwater Natural Pearl (how to read class-level values).
Definition
Freshwater Natural Pearl: A natural pearl produced by a bivalve (5.21) mollusc (5.121) living in freshwater (5.76).
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): §5.78, p.30 (locator checked 2026-09-25)
- Fact checked on
- 2026-09-25
Freshwater Natural Pearl — composition (chemistry): relatively rich in trace elements such as Mn, and relatively poor in Sr, S, Na and Mg.
GB/T 16553—2017
- Does this standard apply
- applies to this entry
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.3.1 Chemical composition · Freshwater natural pearl (locator checked 2026-09-28)
- Fact checked on
- 2026-09-26
Structure
Freshwater Natural 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
- natural pearl (the whole class)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.3.1 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Durability
Mohs hardness2 sources compared
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))
Freshwater Natural Pearl — Mohs hardness: 2.5–3
GIA Gem Encyclopedia
- Qualification
The clause we cite covers the whole species. This entry is only one variety of it.
Source & check 2026-09-20
- Source
- GIA Gem Encyclopedia — Pearl (Gemological Institute of America): Section “Facts”, “Mohs Hardness” (locator checked 2026-09-28)
- Fact checked on
- 2026-09-20
Freshwater Natural Pearl — Mohs hardness: 2.5–4.5
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- natural pearl (the whole class)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.3.1 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Freshwater Natural Pearl — cleavage: generally not seen on an aggregate
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- natural pearl (the whole class)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.3.1 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
stability2 sources compared
Freshwater Natural Pearl — stability: In addition to normal care, natural and cultured pearls shall have special care requirements that include instructions that they should not be worn while carrying out heavy work, should be kept away from all solvents and acids and not be subjected to high temperatures as well as ultrasonic cleaning.
CIBJO Pearl Book 2024
- Treatment state
- untreated
Source & check 2026-09-21
- Source
- CIBJO Blue Book — Pearl Book (Pearl Commission 2024-1) (CIBJO): §7 Annex B, 7.2, p.49 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Freshwater Natural Pearl — stability: effervesces in acid; burns and turns brown if overheated.
GB/T 16553—2017
- Treatment state
- untreated
- Does this standard apply
- applies to this entry
- What this covers
- natural pearl (the whole class)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.3.1 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Physical properties
Freshwater Natural Pearl — density: 2.66–2.78 g/cm³
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- Qualification
After this range the clause we cite adds that it seldom exceeds 2.74.
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.3.1 Density · Natural freshwater pearl (locator checked 2026-09-28)
- Fact checked on
- 2026-09-26
Freshwater Natural 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
- natural pearl (the whole class)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.3.1 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Optical
Freshwater Natural Pearl — optic character: aggregate
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- natural pearl (the whole class)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.3.1 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Freshwater Natural Pearl — refractive index: 1.53–1.68
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- natural 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): §5.3.1 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Freshwater Natural Pearl — birefringence: not measurable on an aggregate
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- natural pearl (the whole class)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.3.1 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Freshwater Natural 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
- natural pearl (the whole class)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.3.1 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Quality factors
Freshwater Natural Pearl — quality factor (lustre): pearly
GB/T 16553—2017
- Treatment state
- untreated
- Does this standard apply
- applies to this entry
- What this covers
- natural pearl (the whole class)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.3.1 (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.
This material (RI / SG midpoints): 1.605 / 2.72; Closest values: 1Giant Clam Shell 1.605 / 2.79, 2Larimar 1.62 / 2.82, 3Natural Conch Pearl / Natural Melo Pearl 1.595 / 2.84, 4Aquamarine 1.58 / 2.79, 5Turquoise 1.63 / 2.65
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
Related CIBJO terms
- Freshwater
a body of water that is non-saline, e.g., rivers, lakes, ponds and marshes.
CIBJO Blue Book — Pearl Book (Pearl Commission 2024-1) (CIBJO): §5.76, p.29
- Scottish pearls
natural freshwater pearls from Margaritifera margaritifera (9.41) in Scotland.
CIBJO Blue Book — Pearl Book (Pearl Commission 2024-1) (CIBJO): §5.178, p.43
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): §9.2 Actinonaias pectorosa · §9.6 Amblema plicata · §9.17 Cumberlandia monodonta · §9.18 Cyclonaias tuberculata · §9.19 Cyrtonaias tampicoensis · §9.20 Ellipsaria lineolata · §9.21 Elliptio crassidens · §9.23 Fusconaia flava · §9.31 Hyriopsis cumingii · §9.35 Lasmigona complanata · §9.36 Ligumia recta · §9.41 Margaritifera margaritifera · §9.42 Megalonaias nervosa · §9.53 Obliquaria reflexaria · §9.65 Potamilus purpuratus · §9.66 Potamilus alatus · §9.67 Proptera purpurata · §9.70 Quadrula metanevra · §9.71 Quadrula nodulata · §9.72 Quadrula pustulosa · §9.73 Quadrula quadrula · §9.75 Reginaia ebenus
Testing and market
The CIBJO laboratory protocol covers Freshwater Natural Pearl under “Pearl” (§6.2.11): 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.
Clause-level definitions
The clause-level definition of Freshwater Natural Pearl is based on GB/T 16552—2017 Annex A, registered under the term Freshwater Natural Pearl and defined as a natural pearl formed inside a freshwater mollusc. The cross-check result is that it is listed directly in GB/T, and no identically titled standalone entry was found in CIBJO.
This table scrolls sideways on narrow screens.
| Term | Clause | Definition | Cross-check |
|---|---|---|---|
| Freshwater Natural Pearl | GB/T 16552-2017 Annex A | Natural pearl formed in a freshwater mollusc | Listed directly by GB/T; CIBJO carries no standalone entry under the same name. |
Evidence and sources
Authority basis and clause sources
Sources
- CIBJO – The World Jewellery Confederation. Gemmological Laboratories Book (Blue Book), Gemmological Commission 2024-1.
- CIBJO – The World Jewellery Confederation. The Gemstone Book (Blue Book), 2022.
- SAMR / SAC (China). GB/T 16552—2017 Gems — Nomenclature.
- CIBJO – The World Jewellery Confederation. The Pearl Book (Blue Book), 2024.
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 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 (Freshwater Natural Pearl) is marked.
- Pearl
Sub-entries (16)
- Abalone Pearl
- Akoya Cultured Pearl
- Baroque Cultured Pearl
- Blister Pearl
- Circled Cultured Pearl
- Cultured Pearl
- Freshwater Cultured Pearl
- Freshwater Natural Pearl
- Keshi Cultured Pearl
- Natural Conch Pearl / Natural Melo Pearl
- Natural Pearl
- Saltwater Cultured Pearl
- Saltwater Natural Pearl
- South Sea Cultured Pearl
- Tahitian Cultured Pearl
- White South Sea Cultured Pearl
This table scrolls sideways on narrow screens.
| Page | Content | Status |
|---|---|---|
| Browsing family | Pearl and molluscan shell materials | Live |
| Treatments recorded for this material | Bleached (via parent material), Dyed (via parent material) | Live |
| Related articles | To be added (placeholder) | Planned |
Who maintains this page
The material facts in the Freshwater Natural 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; 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.