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Natural organic and biogenic materials · Organic or biogenic material · Natural identity; treatment status unknown
Horny Coral
One of the two types of coral distinguished when identifying coral under GB/T 16553: made almost entirely of organic matter, it does not react to hydrochloric acid (calcareous coral fizzes in it). 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 Horny Coral forms and what gives its colourFormation setting, process and timescale, each finding graded and sourced
- How to identify Horny CoralIdentification points from the research literature
- Hardness, density and refractive index of Horny CoralEach value with its source and check date
- Horny Coral 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 Horny CoralThe listing name to use; what must be disclosed before sale
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
Horny coral is a class of coral defined by skeletal composition: the skeleton is almost entirely organic matter, as opposed to the calcium-carbonate-dominated 'calcareous coral'. The documented non-calcareous (horny) example is black coral: composed of protein and chitin, very dark brown to black, quite flexible, spiny and tree-like, of the order Antipatharia (subclass Hexacorallia). Because of its non-calcareous skeleton, horny coral has a much lower specific gravity than calcareous coral. It is a biogenic material; after harvesting and working it can be used as ornament/adornment, and the specific species and any treatment require identification. Black coral (the entire order Antipatharia, including the genus Antipathes) is listed in CITES Appendix II. GB/T 16553 is a nomenclature/identification standard whose full text is unavailable, and no clause numbers are relied on for the formation content.
Scope: Applies to explaining the composition, biogenic origin and known examples (black coral) of horny coral as a class of corals 'with a predominantly organic skeleton', and its CITES listing; not applicable to determining the specific species, locality, treatment or value from the name.
Sources CIBJO Coral Blue Book 2024 · CIBJO Coral Information Sheet
Where it forms
Marine setting: corals are marine invertebrates forming non-calcareous (horny/protein-chitin) skeletons.
Sources CIBJO Coral Information Sheet
Deep, current-swept settings: black coral (Antipatharia) occurs in strong-current environments, at great depths.
Sources CIBJO Coral Information Sheet
How it forms, step by step
Coral polyps (a colony, e.g. black coral) grow.
Sources CIBJO Coral Blue Book 2024 · CIBJO Coral Information Sheet
They form a non-calcareous skeleton composed of protein and chitin.
Sources CIBJO Coral Blue Book 2024 · CIBJO Coral Information Sheet
After harvesting and working it can be used as ornament/adornment; bleaching can yield a golden colour (to be disclosed).
Sources CIBJO Coral Blue Book 2024 · CIBJO Coral Information Sheet
Link to appearance
It appears as a very dark brown to black, flexible, spiny, tree-like skeleton; but appearance cannot substitute for identifying the species and the calcareous/non-calcareous category.
Sources CIBJO Coral Blue Book 2024 · CIBJO Coral Information Sheet
Timescale
The cited sources give no absolute age or growth duration for horny coral.
Sources CIBJO Coral Blue Book 2024 · CIBJO Coral Information Sheet
Related base materials
- Coral: A class of coral defined by skeletal composition (non-calcareous/horny skeleton); a classification name, not a mineral species
Supporting findings
Horny coral is a biogenic material forming a non-calcareous skeleton; its specific gravity is much lower than that of calcareous coral (black coral SG≈1.34).
Evidence grade AScope: A biogenic-process statement; a given sample's specific gravity and species require measurement.
Sources CIBJO Coral Information Sheet
Recorded localities
This is an organic material; its localities are the harvest or culture areas (waters or species ranges) recorded by authoritative sources.
Seas and coasts
- Worldwide seas (black coral)Black coral (Antipatharia) occurs almost worldwide
Sources CIBJO Coral Blue Book 2024
- Caribbean SeaBlack coral
Sources CIBJO Coral Blue Book 2024
- Waters off Hawaii, United StatesBlack coral; golden coral (Kulamanamana haumeaae)
Sources CIBJO Coral Blue Book 2024
- Oceania watersBlack coral
Sources CIBJO Coral Blue Book 2024
- Waters off Alaska, United StatesGolden coral (Primnoidae)
Sources CIBJO Coral Blue Book 2024
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 the origin determination guide and the overview of recorded localities.
How it is identified
The appearance of horny-coral can be imitated, so appearance alone cannot confirm it. Imitation coral lacks the chemical composition, physical properties or structure of natural coral; identification requires laboratory methods — examining internal features such as the different polished lustre of filled fissures at 10× magnification, together with instrumental testing of chemistry and structure — while dyed, filled, impregnated and coated treatments must be detected and disclosed at sale. Limitations: some treatments and imitations are visible only under magnification or instrumentation, and the conclusion must be issued by an accredited gemological laboratory through testing rather than inferred from appearance.
Evidence grade AScope: Identification and separation points; testing must be performed by an accredited gemological laboratory, and no self-test thresholds are given.
Sources CIBJO Coral Blue Book 2024 · CIBJO Gemstone Book 2022
Other research findings
Horny coral is a class of coral defined by skeletal composition (the skeleton is almost entirely organic matter), as opposed to the calcium-carbonate-dominated calcareous coral; it is a material-classification name, not a mineral species.
Evidence grade BScope: A classification/identity-boundary judgement; the full text of GB/T 16553 could not be obtained, so the conclusion that depends on it could not be checked against the standard and no clause of it is cited.
Sources CIBJO Coral Information Sheet · CIBJO Coral Blue Book 2024
The documented non-calcareous (horny) coral example is black coral, composed of protein and chitin and belonging to the order Antipatharia.
Evidence grade AScope: Composition of black coral (the non-calcareous example); does not infer the species of all horny corals.
Sources CIBJO Coral Blue Book 2024
Black coral (the entire order Antipatharia, including the genus Antipathes) is listed in CITES Appendix II; trade legality depends on species and permits.
Evidence grade AScope: Species-related CITES level; CITES levels are current status, updated at CoPs, and 'protected' is not a blanket trade ban.
Sources CIBJO Coral Information Sheet · CIBJO Coral Blue Book 2024
The CITES Appendices valid from 5 March 2026 list the whole order of black corals (Antipatharia spp.), the documented example of horny coral, in Appendix II. A listing covers the whole animal, live or dead, and its parts and derivatives fall in the same Appendix.
Evidence grade AScope: States only what is printed in the CITES Appendices for black corals (Antipatharia); other horny corals depend on their own listings. National law, exemptions and permits are not covered. Not legal advice.
Sources CITES Appendices (2026)
Limits of this research
- Research status: Formation, occurrence or other material-specific findings found in authoritative sources
- Horny coral is a material-classification name (skeleton almost entirely organic), not a mineral species; the documented example is black coral (Antipatharia).
- The full text of GB/T 16553 could not be obtained, so no clause of it is cited and the conclusion that depends on it could not be checked against the standard.
- CITES Appendix II (Antipatharia); 'protected' is not a blanket trade ban—legality depends on species and permits.
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
- Horny coral (state the variety and any treatments)
GB/T 16553—2017 §5.3.4.3
Construction or treatment status
Natural identity; treatment status unknown
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
Horny Coral's material identity has open questions that are not fully settled; this site lists it as "Horny coral (state the variety and any treatments)" pending further verification.
Evidence
- GB/T · §5.3.4.3
What this means for you
Before buying, check the recommended listing name "Horny coral (state the variety and any treatments)" 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
- 2026-09-26
Care and wear
No care facts are recorded for this entry itself. Its parent material has care records: see Coral.
VerifyNames, standards, technical facts, clauses and sources
Names
Recommended listing nameThe Chinese formal name for Horny Coral is given in GB/T 16553—2017, which describes it mineralogically as coral made almost entirely of organic matter. The suggested listing name is Horny Coral (stating variety and treatment). Names in four languagesThe names are given in Simplified Chinese, Traditional Chinese, English (Horny Coral) and Japanese (a kanji and katakana name, pending check); the Japanese GSJ wording for this name is not yet verified by this site, and the Japanese name is the entry's own. Institution usageAmong authority wordings, the FTC and CIBJO source texts have no wording for Horny Coral (checked), and bodies without a recorded wording show the entry's own English name, Horny Coral, which does not represent their position; GIA and Gem-A have not been checked.
- GSJ (Japan) formal name
- 角質サンゴ（待核） (not yet checked for this body — the entry's own Japanese name is shown)
- Chinese formal name
- 角质珊瑚 (GB/T 16553—2017 §5.3.4.3)
- Mineralogical name
- Horny coral: coral made almost entirely of organic matter (GB/T 16553 §5.3.4.3)
Four-language names
- 简体中文
- 角质珊瑚
- 繁體中文
- 角質珊瑚
- English
- Horny Coral
- 日本語
- 角質サンゴ（待核）
See also: Misleading and prohibited trade names · Supplementary name index
Classification
- Origin
- Natural materials
- Material domain
- Natural organic and biogenic materials
- Browsing family
- Coral materials
- Identity tier
- Organic or biogenic material
- Mineral chemical class
- Not applicable
- Construction or treatment status
- Natural identity; treatment status unknown
What it is and how it's identified
Horny Coral is registered from GB/T 16553—2017 with a Mohs hardness of 2–3, and the general note states that hardness alone is not enough to judge durability; density is 1.3–2.12 g/cm³, the cited clause giving 1.35 with a tolerance of +0.77/−0.05, and the registered limits are derived from the clause value and tolerance; refractive index is 1.55–1.58, the cited clause reading coming from what is typically obtained by the spot method, a typical value rather than an absolute limit, with a clause value of 1.56–1.57 and a tolerance of ±0.01 from which the registered limits are derived. The body colour of untreated Horny Coral is black, golden yellow or yellowish brown; the qualification notes that the colours the cited clause lists for calcareous coral also include yellow, so Horny Coral and calcareous coral must be distinguished by composition, and the same clause states that Horny Coral does not react with hydrochloric acid whereas calcareous coral effervesces.
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”.
Durability
Horny Coral — Mohs hardness: 2–3
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
- General note
- hardness only, not durability
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.3.4 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Physical properties
Horny Coral — density: 1.3–2.12 g/cm³
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- Qualification
The clause we cite gives 1.35, with a stated tolerance of +0.77 / -0.05. The range shown here is worked out from that.
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.3.4 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Optical
Horny Coral — refractive index: 1.55–1.58
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- Qualification
The clause we cite gives this as a value commonly read by the spot (distant-vision) method. It is a common value, not an absolute limit. The clause we cite gives 1.56–1.57, with a stated tolerance of ±0.01. The range shown here is worked out from that.
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.3.4 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Horny Coral — body colour: black, golden yellow or yellowish brown
GB/T 16553—2017
- Treatment state
- untreated
- Does this standard apply
- applies to this entry
- Qualification
The clause we cite also lists yellow for calcareous coral, and the two classes are told apart by composition: the same clause says horny coral does not react with hydrochloric acid while calcareous coral effervesces.
- General note
- colour alone is not identity
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.3.4 (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): 1.565 / 1.71; Closest values: 1Mammoth Ivory 1.53 / 1.75, 2Ivory 1.535 / 1.85, 3Coral 1.57 / 2, 4Plastic 1.58 / 1.3, 5Turtle Shell 1.545 / 1.31
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
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.
- AQSIQ / SAC (China). GB/T 16553—2017 Gems — Testing.
- SAMR / SAC (China). GB/T 16552—2017 Gems — Nomenclature.
- CIBJO – The World Jewellery Confederation. The Coral Book (Blue Book), 2024.
- eCFR (United States). 16 CFR Part 23 — Guides for the Jewelry, Precious Metals, and Pewter Industries.
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 Coral on this site: 12 entries listed by this site's parent-entry links; synthetic, treated and similar entries carry their recorded state after the name; this page (Horny Coral) is marked.
This table scrolls sideways on narrow screens.
| Page | Content | Status |
|---|---|---|
| Browsing family | Coral materials | Live |
| Related articles | To be added (placeholder) | Planned |
Who maintains this page
The material facts in the Horny Coral 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.