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Natural organic and biogenic materials · Organic or biogenic material · Natural identity; treatment status unknown

Jet

Also known asBlack amber (not to be used as a name) · Gagat

A dense organic material formed from lignitized wood, listed as "Jet" in GB/T Annex A Table A.3; it is not amber. This page compares how the major standards and institutions name it, what must be disclosed when selling it, whether it can be worn every day, how it is treated and identified, and which source each conclusion comes from.

Price, rarity and origin are outside the scope of this wiki.

Edited by RalphReviewed by JuneLast updated 2026-10-12Who maintains this page

FAQCare and wear

Questions people ask about Jet

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

Q1What is jet, and is it a stone?

Jet is a hard variety of lignite coal: coniferous wood buried in sediments is altered over geological time, by coalification, into jet.GIA Reading List: Whitby JetIt is an organic material, not a mineral species, and its name comes from the Latin gagates, after the town of Gagae.GIA Reading List: Whitby JetIts main element is carbon, and it may contain hydrogen and oxygen.GB/T 16553—2017

Q2How can you tell real jet from imitations?

Jet can resemble other dark materials, and appearance cannot establish its identity or treatment; that takes an accredited laboratory.CIBJO Gemstone Book 2022Jet becomes electrically charged when rubbed.GB/T 16553—2017Its streak is brown.GB/T 16553—2017Whether one particular bead is natural, treated or synthetic — only a laboratory report can settle that.What this page can answer

Q3Is jet jewellery fragile?

CIBJO notes that its low hardness makes it scratch easily and that it can fracture or be brittle, so it should be worn with care.CIBJO Gemstone Book 2022Prong, bezel and channel settings call for caution, and flush and pavé are best avoided.Gems & Gemology 1987 (Martin)

Q4How should jet be cleaned and cared for?

Ultrasonic and steam cleaners should be avoided.Gems & Gemology 1987 (Martin)Keep it away from heat, because it burns easily, and from acids, which dull the surface.Gems & Gemology 1987 (Martin)Display-case heat, sunlight and artificial light are rated relatively safe.Gems & Gemology 1987 (Martin)

Q5Where is jet found?

Jet occurs as irregular, horizontal coal-like seams in certain layered sedimentary rocks, mainly shales, as on the Whitby coast of England.GIA Reading List: Whitby Jet

Q6What does jet symbolize, and does it have protective or healing powers?

There is no scientific evidence that jet 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 as adornment: at least 5000 years, popular with the Romans, and widely worn as mourning jewellery in the Victorian period after 1861.GIA Reading List: Whitby JetThe V&A holds a Spanish figa amulet of 1800–1900, a fist carved in jet and mounted in silver, which its catalogue calls an old charm against the evil eye.Cultural records

Q7What makes good-quality jet?

For Whitby jet, hard jet is prized for jewellery and ornaments; soft jet was also used when demand was high, and Victorian soft-jet beads are now developing networks of surface cracks that eventually break them apart.Whitby Museum

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

The geological term "jet" denotes a hard form of lignite coal that comes from coniferous wood: wood of that kind, once buried in sediments, is coalified over geologic time and becomes jet. It is an organic substance — lustrous and opaque, black or dark gray — that can be carved, or worked on a small lathe, and takes a high polish. Jet is found occasionally as irregular horizontal seams resembling coal within particular layered sedimentary rocks, chiefly shales, as around Whitby on the English coast; it is organic material, not a mineral species.

Scope: Applies to the identity of jet as a natural organic material (hard lignite) and to an overview of its coal-forming origin; does not address specific deposits or worked pieces.

Sources GIA Reading List: Whitby Jet

Where it forms

Coal-like seams, irregular and horizontal, within layered sedimentary rocks, chiefly shales — for example on the Whitby coast of England.

Sources GIA Reading List: Whitby Jet

How it forms, step by step

  1. Sediments bury wood of coniferous trees.

    Sources GIA Reading List: Whitby Jet

  2. Over geologic time, alteration (coalification) converts the wood into hard lignite.

    Sources GIA Reading List: Whitby Jet

  3. Within layered sedimentary rocks, mostly shales, it appears as coal-like seams that are irregular and horizontal.

    Sources GIA Reading List: Whitby Jet

  4. What results is an organic material — lustrous and opaque, black or dark gray — employed for carving and for turning.

    Sources GIA Reading List: Whitby Jet

Link to appearance

Jet is lustrous, opaque, and black or dark gray; being uniformly coloured and taking a high polish makes it suitable for jewellery and carving.

Sources GIA Reading List: Whitby Jet

Timescale

Coalification occurs "over geologic time" (no specific figure given).

Sources GIA Reading List: Whitby Jet

Related base materials

  • Lignite (brown coal): Jet is a hard lignite derived from the carbonisation of coniferous wood

Supporting findings

The geological term "jet" denotes a hard variety of lignite coal. Over geologic time, coniferous wood buried in sediments undergoes alteration — coalification — and jet is what results.

Evidence grade A

Scope: Applies to jet's coalification origin; not a specific locality.

Sources GIA Reading List: Whitby Jet

Now and then jet occurs in the form of coal-like seams — irregular and horizontal — within particular layered sedimentary rocks, chiefly shales; the Whitby coast is one example.

Evidence grade A

Scope: Describes its occurrence; Whitby is the best-known but not the only source.

Sources GIA Reading List: Whitby Jet

Recorded localities

Authoritative sources list the localities below; the list is not exhaustive.

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

Europe

Seas and coasts

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.

Human use and museum objects

Jet has been used for personal adornment for at least 5000 years, became popular with the Romans, and was widely used in mourning jewellery in the Victorian period (after 1861).

Evidence grade A

Scope: Concerns human-use history; not geological formation.

Sources GIA Reading List: Whitby Jet

In these collections the earliest datable jet beadwork comes from Iran, broadly the 8th-13th century (Met 40.170.405, 38.40.90, 48.101.250, some recorded only as "probably jet"); from the 19th-20th century jet appears mainly in European and American personal ornament and mourning jewellery (e.g. Met 2009.300.5744, 2009.300.1594, C.I.65.28.2).

Evidence grade A

Scope: Applies to collection objects recorded as jet, or "probably jet", from Iran, Europe and America; other black organic materials are not covered.

Sources The Met 40.170.405 · The Met 38.40.90 · The Met 48.101.250 +2

The Metropolitan Museum of Art holds a number of objects worked in jet. The earliest group comes from Iran, broadly the 8th-13th century: acc. 40.170.405 (bead, 9th-10th century, material recorded as Jet), acc. 38.40.90 (button or bead, 10th-11th century, "Stone, probably jet") and acc. 48.101.250 (fragments of a bead, 8th-13th century, Jet). Some Iranian beads are recorded only as "probably jet", so the identification is not certain in every case. Jet was thereafter used mainly for personal ornament and mourning jewellery in Europe and America: a necklace of 1900-1910 (acc. 2009.300.5744, jet and crystal), a choker of 1900-1915 (acc. 2009.300.1594), and jet beading on a French evening dress of 1940-43 (acc. C.I.65.28.2). Together these show the use of jet for beadwork and ornament in West Asia and, later, in the modern West.

Sources The Met 40.170.405 · The Met 38.40.90 · The Met 48.101.250 +3

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

600800100012001400160018002000Met 48.101.2508th–13th centuryMet 40.170.4059th–10th centuryMet 38.40.9010th–11th centuryMet 2009.300.57441900–1910Met 2009.300.15941900–1915Met C.I.65.28.21940–43
Dates of museum objectsDates from the museums' open-access records (CC0); each bar spans the whole period named in the record, with qualifiers such as “early” or “possibly” kept in the label rather than turned into a narrower range; an arrow marks a record that reads “before” or “after” a yearSource: The Met / Cleveland Museum of Art open-access records

Cultural records for this material: Evil eye.

How it is identified

Black organic materials such as jet may resemble other dark substances, and appearance cannot establish their identity or treatment status. Identification requires an accredited laboratory to test composition and internal features with instruments; for suspected treatment, trade guidance calls for prudent disclosure rather than a conclusion drawn from appearance.

Evidence grade A

Scope: Jet identification and treatment judgement require an accredited laboratory; uncertainty should be disclosed prudently.

Sources CIBJO Gemstone Book 2022

Other research findings

A lustrous and opaque substance, jet is organic and black or dark gray; in organic terms it is a lignite.

Evidence grade A

Scope: Describes its compositional category and appearance; not a specific sample.

Sources GIA Reading List: Whitby Jet

Jet is an organic material, not a mineral species; the name derives from the Latin gagates, from the town of Gagae.

Evidence grade A

Scope: Defines it as organic and gives the name origin; not genesis.

Sources GIA Reading List: Whitby Jet

Whitby jet occurs in hard and soft varieties, among others. Hard jet is prized for jewellery and ornaments; soft jet was also used in times of high demand, and Victorian soft-jet beads are now developing networks of surface cracks that eventually break them apart.

Evidence grade B

Scope: Covers Whitby jet as described by a local museum; not a grading standard, not a statement about the value of any piece, and not a rule for jet from other localities.

Sources Whitby Museum

Limits of this research

  • Research status: Formation, occurrence or other material-specific findings found in authoritative sources
  • The source is a GIA historical reading list; its genetic conclusion is cited from early literature (e.g. Seward 1901) and is used as stated.
  • The source gives no specific numerical age for coalification, only a "geologic time" scale.

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
Jet

GB/T 16552—2017 Table A.3 “Jet” · CIBJO Gemmological Laboratories Book 2024 §7.2.2.8 “Jet”

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

Not amber; it must be distinguished from plastic, glass and other imitations.

Evidence

  • GB/T · Table A.3, row 煤精 (Jet)

What this means for you

Before buying, check the recommended listing name "Jet" and any disclosed treatments on this page, and ask the seller for a grading report if in doubt.

Known uncertainty

Last reviewed
2026-09-01

Care and wear

Normal care for every gemstone (CIBJO Gemstone Book §6.1), in brief:

  • Handle it gently.
  • Store pieces apart when not worn, so they cannot scratch each other.
  • Clean with warm soapy water and a soft brush.
  • Use ultrasonic cleaners only with caution.

The §6.1 wording and the full list of §6.2 special-care letters cited on this page are on the general gem care page.

Care

care (cleaning)2 sources compared

Jet — care (cleaning): Some stones are susceptible to damage from ultrasonic cleaning. Do not expose them to ultrasonic cleaning.

CIBJO Gemstone Book 2022

CIBJO Gemstone Book §6.2:special-care code j

Treatment state
any treatment state
Source & check 2026-09-25
Source
Fact checked on
2026-09-25

Jet — care (cleaning): ultrasonic and steamer: avoid.

Gems & Gemology 1987 (Martin)

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

Jet — care (wear): low hardness, so it scratches easily; wear with care; cleaves or fractures easily or is brittle (e.g. rubbed facet edges); wear with care.

CIBJO Gemstone Book 2022

CIBJO Gemstone Book §6.2:special-care code a, special-care code b

Treatment state
any treatment state
Source & check 2026-09-25
Source
Fact checked on
2026-09-25

Jet — care (setting): prong, bezel and channel: use caution; flush and pavé: avoid.

Gems & Gemology 1987 (Martin)

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

Jet — care (repair): jeweller's torch, pickle pot, polishing and thermal shock: avoid; note: avoid heat, as it burns easily; acids dull the surface.

Gems & Gemology 1987 (Martin)

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

Jet — care (display): heat in the display case, sunlight and artificial light: relatively safe.

Gems & Gemology 1987 (Martin)

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

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

Common care questions and matching entries

CleaningCare of Jet: the CIBJO Blue Book — Official Gemstone Book states that, regardless of treatment status, it should not be cleaned ultrasonically; Martin's Gemstone Durability: Design to Display states that untreated Jet should avoid ultrasonic and steam cleaning. WearOn wear, the CIBJO Blue Book — Official Gemstone Book states, regardless of treatment status, that Jet is soft, scratches easily and is prone to breaking, so wear it with care. SettingOn setting, Martin's Gemstone Durability: Design to Display states for untreated Jet that prong, bezel and channel settings need caution, and tension and pavé settings should be avoided. Heat and repairOn heat and repair, Martin's Gemstone Durability: Design to Display states for untreated Jet that the torch, polishing and thermal shock should all be avoided, adding that heat should be avoided as it burns very easily; on chemicals, the same source states for untreated Jet that post-soldering pickle should be avoided, as acid dulls the surface. Light and displayOn light and display, the same source states for untreated Jet that heat, daylight and artificial light in a display case are relatively safe.

This table scrolls sideways on narrow screens.

QuestionMatching entries
Can it go in an ultrasonic or steam cleaner?care (cleaning); ultrasonic and steamer: avoid
Heat and thermal shockjeweller's torch, pickle pot, polishing and thermal shock: avoid; note: avoid heat, as it burns easily; acids dull the surface
Light and displayheat in the display case, sunlight and artificial light: relatively safe
Wearing limits (knocks, settings)low hardness, so it scratches easily; wear with care; cleaves or fractures easily or is brittle (e.g. rubbed facet edges); wear with care; prong, bezel and channel: use caution; flush and pavé: avoid

Care entries by treatment state

The same entries grouped by the treatment state each applies to; each links to its full wording and source. Letters are CIBJO special-care codes, explained on the gemstone care page.

any treatment state

untreated

VerifyNames, standards, technical facts, clauses and sources

Names

For Jet, "Gagat" is recorded with no restriction on use as a name, while "Black amber" must not be used as a name (16 CFR Part 23 §23.1); 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 namesThe GB/T 16552—2017 formal name for Jet is set out in Table A.3, and the suggested listing name is Jet. Names in four languagesThe four-language names cover Simplified Chinese, Traditional Chinese, English (Jet) and Japanese; the GSJ (Japan) wording for the entry's own Japanese name is not yet verified by this site. Institution usageOn authority wording, the CIBJO Gemmological Laboratories Book 2024 has Jet on record; the FTC text on file has no wording for this name (checked); GIA and Gem-A are unchecked, and the entry's English name shown for bodies without a record does not represent their position. Trade and mineralogical namesThe mineralogical name is Jet, a compact organic material formed from lignitised wood. Sub-names and unacceptable namesBlack amber is a market name, a misnomer that may not be used as a name and serves only as a search term. Candidate search termsLignite is a synonym, used only as a candidate search term, based on the GB/T 16552 revision consultation draft (2023, not in force); Gagat is an older name, from the CIBJO Gemstone Book 2022.

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 (2)
GagatEnglishhistorical namematched automaticallyno restriction recordedCIBJO Gemstone Book 2022 Annex 8 “Gagat”
褐煤Simplified Chinesesynonymsearch candidate onlyno restriction recordedGB/T 16552 revision draft for comment (2023, not in force) Table A.3; GB/T 16552—2017 Table A.3 “Jet”; Note: Draft standard for comment, not in force.
not to be used as a name (1)
Black amberEnglishmarket namematched automaticallynot to be used as a name16 CFR Part 23 §23.1; Note: Misnomer; kept for search only.

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

Authority wording

GIA, FTC, CIBJO, Gem-A
Jet (on record for CIBJO (CIBJO Gemmological Laboratories Book 2024); 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
ジェット／黒玉 (not yet checked for this body — the entry's own Japanese name is shown)
Chinese formal name
煤精 (GB/T 16552—2017 Table A.3)
Mineralogical name
Jet: compact organic material derived from lignitic wood
Trade names and synonyms
Gagat (historical name)Not to be used as a name: Black amber (market name)

Four-language names

简体中文
煤精
繁體中文
煤精
English
Jet
日本語
ジェット／黒玉

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

Classification

Origin
Natural materials
Material domain
Natural organic and biogenic materials
Browsing family
Plant-derived 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

The main element in the composition of Jet is C, and it may contain H and O; its structure is amorphous. Mohs hardness is 2–4, cleavage none, birefringence none, optic character isotropic, and it is opaque; in the infrared spectrum, vibrations of organic functional groups produce characteristic absorption bands in the mid-infrared region. Density 1.3–1.34 g/cm³ is derived from the cited clause value 1.32 with tolerance ±0.02. Refractive index 1.64–1.68 is derived from the cited clause value 1.66 with tolerance ±0.02; the clause value of 1.66 is the reading commonly obtained by the spot method, a typical value rather than an absolute limit. When untreated, Jet burns and smells of coal smoke after contact with a hot needle or burning; pleochroism none, fluorescence none; magnification shows conchoidal fracture on the outer surface and banded structure, sometimes with wood grain; lustre is waxy, resinous to vitreous; GB/T 16553—2017 gives the body colour as black or brownish black and CIBJO records black, the two complementing rather than contradicting each other.

Registered material facts

Each row carries its own source and check date and can be cited on its own; “—” means the cited source gives no value, not “none”.

Definition

Jet — composition (chemistry): main element:C;H and O may be contained.

GB/T 16553—2017

Does this standard apply
applies to this entry
Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.3.6 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Structure

Jet — structure (overall): amorphous (not crystalline)

GB/T 16553—2017

Does this standard apply
applies to this entry
Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.3.6 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Durability

Jet — Mohs hardness: 2–4

GB/T 16553—2017

123456789102–4References (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
Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.3.6 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Jet — cleavage: none

GB/T 16553—2017

Does this standard apply
applies to this entry
Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.3.6 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Jet — stability: can burn; gives off a sooty smell when touched with a hot needle or after burning.

GB/T 16553—2017

Treatment state
untreated
Does this standard apply
applies to this entry
Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.3.6 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Physical properties

Jet — density: 1.3–1.34 g/cm³

GB/T 16553—2017

0.51.52.53.54.55.56.57.51.3–1.34
Specific gravitySource: GB/T 16553—2017
Does this standard apply
applies to this entry
Qualification

The clause we cite gives 1.32, with a stated tolerance of ±0.02. The range shown here is worked out from that.

Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.3.6 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Jet — streak: The streak is brown

GB/T 16553—2017

Does this standard apply
applies to this entry
Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.3.6 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Jet — triboelectricity: becomes electrically charged when rubbed

GB/T 16553—2017

Does this standard apply
applies to this entry
Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.3.6 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Optical

Jet — optic character: isotropic material

GB/T 16553—2017

Does this standard apply
applies to this entry
Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.3.6 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Jet — refractive index: 1.64–1.68

GB/T 16553—2017

1.31.72.12.52.93.31.64–1.68
Refractive indexSource: 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 1.66, with a stated tolerance of ±0.02. The range shown here is worked out from that.

Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.3.6 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Jet — birefringence: none

GB/T 16553—2017

Does this standard apply
applies to this entry
Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.3.6 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Jet — transparency: opaque.

CIBJO Gemmological Laboratories Book 2024

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

Jet — pleochroism: none

GB/T 16553—2017

Treatment state
untreated
Does this standard apply
applies to this entry
Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.3.6 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Jet — fluorescence (overall): none

GB/T 16553—2017

Treatment state
untreated
Does this standard apply
applies to this entry
Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.3.6 (locator checked 2026-09-21)
Fact checked on
2026-09-21

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

GB/T 16553—2017

Does this standard apply
applies to this entry
Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.3.6 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Jet — spectrum (infrared): Diagnostic mid-IR bands come from vibrating functional groups (radicals) within the organic material.

GB/T 16553—2017

Does this standard apply
applies to this entry
Source & check 2026-09-22
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.3.6 (locator checked 2026-09-22)
Fact checked on
2026-09-22

Jet — magnification: conchoidal fracture on the outer surface, banded structure, sometimes visible wood-grain striations visible on the exterior.

GB/T 16553—2017

Treatment state
untreated
Does this standard apply
applies to this entry
Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.3.6 (locator checked 2026-09-21)
Fact checked on
2026-09-21

body colour2 sources compared

Jet — body colour: black and brownish black

GB/T 16553—2017

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

In chapter 5 of GB/T 16553—2017, the colour entries of Epidote, Cassiterite, Chrysocolla and other variety clauses also name black or a blackish colour.

General note
colour alone is not identity
Source & check 2026-09-26
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.3.6 (locator checked 2026-09-26)
Fact checked on
2026-09-26

Jet — body colour: black.

CIBJO Gemmological Laboratories Book 2024

Treatment state
untreated
Qualification

In chapter 7 of the CIBJO Gemmological Laboratories Book, the colour descriptions of Magnetite, Melanite, Black Tourmaline 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

How the sources relate

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

complementary, no conflict

Both describe jet as black; GB/T 16553—2017 also lists brownish black.

Quality factors

Jet — quality factor (lustre): waxy, resinous to vitreous

GB/T 16553—2017

Treatment state
untreated
Does this standard apply
applies to this entry
Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.3.6 (locator checked 2026-09-21)
Fact checked on
2026-09-21

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

1.551.61.6511.21.41.61.8Refractive indexSpecific gravity12345Jet

This material (RI / SG midpoints): 1.66 / 1.32; Closest values: 1Plastic 1.58 / 1.3, 2Turtle Shell 1.545 / 1.31, 3Black Coral 1.565 / 1.71, 4Amber 1.54 / 1.03, 5Mammoth Ivory 1.53 / 1.75

Show the full chart (330 registered materials)1.41.51.61.71.81.922.12.22.32.41234567Refractive indexSpecific gravity12345Jet

Outside the full chart's range, drawn as triangles at the edge (RI / SG midpoints): Hematite 3.045/5.12, Synthetic Rutile 2.76/4.26, Rutile 2.753/4.23, Synthetic Moissanite 2.67/3.22

Refractive index × specific gravity (all registered materials)Each dot is one material's registered refractive index and specific gravity (range midpoints, not measurements); gold = this material, dark = the nearest few (picked on this site by distance in RI ÷ 0.02 and SG ÷ 0.1, leaving out near-identical varieties of the same species)Source: each material's registered refractive index and specific gravity facts (GB/T 16553 and others; sources on each entry)

Testing and market

The finding recorded for testing Jet is that no synthetic counterpart of Jet is commercially available, a conclusion that applies irrespective of treatment status. It comes from the CIBJO Blue Book, Official Gemstone Book (Coloured Stone Commission, 2022 edition).

How far testing can go

Jet — synthetic counterpart on the market: No synthetic counterpart of this material is commercially available

CIBJO Gemstone Book 2022

Treatment state
any treatment state
Source & check 2026-09-22
Source
Fact checked on
2026-09-22

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

Clause-level definitions

Jet is recorded as its own entry in the CIBJO Gemmological Laboratories Book 2024 under the entry name Jet, with a direct definition: jet is an opaque black coalified fossil driftwood formed from trees of the Araucariaceae family. The material also appears in GB/T 16552—2017 Annex A Table A.3, and the cross-check result for the two is: defined directly by CIBJO; also present in the GB/T annex.

This table scrolls sideways on narrow screens.

TermClauseDefinitionCross-check
Jet7.2.2.8Jet is an opaque, black coalified fossilized drift wood of trees of the family Araucariaceae. Jet is chemically related to brown coal, or lignite, but Jet is more solid and tough. Distinction criteriaDefined directly by CIBJO; also present in the GB/T annex.

Evidence and sources

Authority basis and clause sources

GB/T 16552—2017
Listed Table A.3 “Jet” · Source
CIBJO Gemmological Laboratories Book 2024
Listed §7.2.2.8 “Jet” · Source

Sources

Further reading

Recorded cultural contexts

Evil eye

The V&A holds a Spanish figa amulet (1800–1900), a fist carved in jet and mounted in silver, which its catalogue entry calls an old charm against the evil eye.

Relation
Historical object material

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Publisher or holderRegionFrom / periodSource and locator
Victoria and Albert MuseumSpain19th centuryVictoria and Albert Museum, London — museum no. M.22-1917: silver-mounted figa (fist) amulet carved in jet, Spain, 1800–1900
museum no. M.22-1917, catalogue entry

Related intention themes

These reviewed links connect this material with LumaLark intention themes. Each label identifies whether the link is a brand interpretation or a historical and cultural record; neither describes an effect or outcome of the 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.

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PageContentStatus
Browsing familyPlant-derived materialsLive
Related articlesTo be added (placeholder)Planned

Who maintains this page

The material facts in the Jet 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.

Facts editor
Ralph
Reviewer
June
How facts are checked
Each fact is matched to the clause it cites; facts checked between 2026-09-21 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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