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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
Opaque Amber
Also known asbutterscotch amber (conditional name) · mila
A Chinese trade name for opaque Amber; GB/T lists it as a sub-name under Amber, and it is not the same as Baltic amber. Also known as butterscotch 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.
What this page can answer
This page covers
- How Opaque Amber forms and what gives its colourFormation setting, process and timescale, each finding graded and sourced
- How to identify Opaque AmberHow far lab testing can go
- Treatments and enhancements of Opaque AmberThe enhancements and treatments the GB/T and JJA/AGL tables list
- Caring for and wearing Opaque AmberCleaning, heat, chemicals and light, as the cited sources give them
- Hardness, density and refractive index of Opaque AmberEach value with its source and check date
- Opaque Amber 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?
- Name origin and history of Opaque AmberHow people have used it
- Listing and disclosing Opaque AmberThe 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
Mila is a Chinese-market colour/transparency trade name for opaque to semi-opaque amber. Its material body is amber, and its formation is inherited from amber: resin secreted by ancient trees tens of millions of years ago hardened and fossilised through burial, volatilisation and polymerisation. Numerous gas-bubble inclusions trapped in the resin give the material a cloudy, opaque look. Mila is not an independent mineral species and is not a synonym for Baltic amber; it describes transparency and appearance only and cannot establish origin, naturalness or treatment.
Scope: Covers the inherited origin and identity boundaries of the trade name for opaque/translucent amber; does not apply to origin, naturalness or treatment assessments of specific samples.
Sources GIA Amber Description
Where it forms
The environment of resin-producing trees in ancient forests; the resin is buried in sediments, in place or after transport, and fossilises.
Sources GIA Amber Description
How it forms, step by step
Ancient trees (commonly conifers) secrete resin.
Sources GIA Amber Description
The resin is buried and, over geological time, volatilises, polymerises and fossilises into amber.
Sources GIA Amber Description
Abundant gas bubbles and inclusions trapped in the resin make the amber cloudy and opaque, the appearance basis for what the trade calls mila.
Sources GIA Amber Description
“Mila” is only a colour/transparency label; it does not change the fact that the parent material is amber.
Sources GIA Amber Description
Link to appearance
The cloudy, opaque look mainly reflects scattering by abundant gas bubbles trapped in the resin; colours range toward yellow to orange, with reddish material interspersed. Appearance cannot be used to infer origin or treatment.
Sources GIA Amber Description
Timescale
GIA states amber formed tens of millions of years ago and must be over one million years old; younger resin is called copal.
Sources GIA Amber Description
Related base materials
- Amber: Parent material (mila is a colour/transparency trade category of amber)
Supporting findings
Amber is a resin-derived organic gem, formed when sap from ancient trees hardened and fossilised tens of millions of years ago.
Evidence grade BScope: Describes the biogenic formation of amber as parent material; mila inherits it as a transparency category.
Sources GIA Amber Description
Amber has a stated age threshold: it must be over one million years old, while younger resin of the same kind is called copal.
Evidence grade BScope: Applies to the amber/copal age boundary; gives no specimen-specific age.
Sources GIA Amber Description
Recorded localities
This is an organic material; its localities are the harvest or culture areas (waters or species ranges) recorded by authoritative sources.
Asia
- MyanmarSource only mentions reddish amber from Myanmar
Sources GIA Amber Description
Europe
- Baltic coast (Germany, Poland, Russia)Still an important source of amber
Sources GIA Amber Description
North America
- Dominican RepublicSource only gives the origin of one lizard-inclusion specimen
Sources GIA Gem Encyclopedia
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
Amber is called the 'gold of the North', its warm lustre used in beads, carvings, pendants, cabochons and items such as cups, bowls and snuff boxes.
Evidence grade BScope: Historical-cultural use; not geological formation or specimen identification.
Sources GIA Amber Description
Other research findings
Mila is a Chinese-market colour/transparency trade category for opaque/semi-opaque amber whose parent material is amber; it is not an independent mineral species nor a synonym for Baltic amber.
Evidence grade CScope: Naming/identity judgement; the cited sources give no authoritative definition of the term 'mila', so it has no standardised name.
Sources GIA Amber Description
Abundant gas-bubble inclusions give amber a cloudy appearance, which is the material basis for the opaque look of amber sold as mila.
Evidence grade BScope: Explains only the bubble-driven cloudiness mechanism; does not show any specimen to be natural or untreated.
Sources GIA Amber Description
Limits of this research
- Research status: Formation, occurrence or other material-specific findings found in authoritative sources
- None of the cited sources gives an authoritative definition of the Chinese trade term 'mila'; the identity judgement rests on authoritative facts about the parent material amber.
- Whether a specimen was heat- or oxidation-treated is not covered; the name cannot evidence naturalness or origin.
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
- Opaque Amber (Chinese trade name: Mila)
GB/T 16552—2017 Table A.3 “Amber”
Construction or treatment status
Natural identity; treatment status unknown
Treatments recorded for this material: Heated / Heat-treated (via parent material), Filled / Fracture-filled (via parent material), Coated (via parent material), Irradiated (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
"Opaque Amber (Chinese trade name: mila)" is a market name rather than a mineral species name; before using it, verify: Trade name rather than a mineralogical species name.
Evidence
- GB/T · Table A.3, row 琥珀 (Amber)
What this means for you
Before buying, check the recommended listing name "Opaque Amber (Chinese trade name: Mila)" 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
- Trade name rather than a mineralogical species name.
- Suggested listing name
- Opaque Amber (Chinese trade name: Mila)
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.
The item-by-item care advice that the GIA Care and Cleaning Guide gives for the whole class, and so for Opaque Amber, is set out in full under care on the Amber entry.
Care
Each row's “Source & check” expands to the full source; the date beside it is the fact check date.
Treatments and identification leads
One row per treatment, with three standards side by side: how often it occurs and how stable it is (CIBJO), its category in GB/T 16552—2017 Table B.1 (this site's paraphrase) and how the JJA/AGL 2025 table lists it. Each CIBJO value links to its entry under “Testing and market”, where the wording and source are given in full.
This table scrolls sideways on narrow screens.
| Treatment | Market frequency (CIBJO) | Stability (CIBJO) | GB/T 16552 category | JJA/AGL listing | Identification leads |
|---|---|---|---|---|---|
| Heating | — | — | Optimization | — | — |
| Filling | — | — | Graded — see §5.4.1, Table 1 | — | — |
| Coating | — | — | Graded — see §5.4.1, Table 1 | — | — |
| Irradiation | — | — | Treatment | — | — |
| Colour change by heating under pressure | — | — | Treatment | — | — |
| Dyeing | — | — | Treatment | — | — |
“—” means the cited source gives no value for that item, not “none”. Source: GB/T 16552—2017 Table B.1 (row for Amber)
Whether a treatment has to show in the name differs between the two rule sets (this site’s paraphrase):
- GB/T 16552—2017: a method classed as treatment has to be stated in the name itself — the method put before the name, or added in brackets after it; a method classed as optimization does not need to appear in the name, though one marked “Optimization (annotation required)” still has to be noted in the quality documents. Source: §5.4.2.1 a), b); §5.4.2.2 a)
- CIBJO Gemstone Book 2022: no longer splits treatments into ones that need specific disclosure and ones that need only general disclosure: every treatment is to be disclosed, and the seller tells the buyer which treatment was used and what special care it calls for. Source: §4.2.5 Note 2, §4.2.5.1, pp.14–15
What this table covers
What this page can give
- Registered treatments, their stability and how often they occur (see the table above)
- Identification leads for each treatment, for use when sending a stone for testing
VerifyNames, standards, technical facts, clauses and sources
Names
Besides Opaque Amber, the name register records "butterscotch amber" and "mila", for which no restriction on use as a name is recorded.
Standard and listing namesThe Chinese formal name for Opaque Amber is mila, from GB/T 16552—2017 Table A.3; the suggested listing name is “Opaque Amber (Chinese trade name: mila)”. Trade and mineralogical namesTrade names and synonyms are mila (pinyin, Chinese trade name) and butterscotch amber; butterscotch amber refers only to a particular colour, is not equivalent to mila and is matched only once the conditions are confirmed. Mineralogically, mila is a Chinese trade category of colour and transparency, not a separate mineral and not a synonym of Baltic amber. Institution usageAmong authority wordings, the FTC and CIBJO source texts have no wording for Opaque Amber (checked), and the wordings of 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. In the qualifier taken from the entry's own English name, the English names shown for GIA, Gem-A, FTC and CIBJO are all followed by “Chinese trade name mila”. Names in four languagesThe four-language names are given in Simplified Chinese, Traditional Chinese, English (Opaque Amber, Chinese trade name mila) and Japanese (opaque amber, with the Chinese market name mila in kanji and katakana). The entry's own Japanese name is likewise opaque amber, and the Japanese GSJ wording for it is not yet verified by this site.
Name register
Every name recorded for this entry, with how it is classified, whether it may be matched to this entry automatically, whether it may be used as a product name, and the clause it rests on.
This table scrolls sideways on narrow screens.
| Name | Type | Matching | Use as a name | Basis |
|---|---|---|---|---|
| no restriction recorded (2) | ||||
| butterscotch amberEnglish | market name | matched only once the condition is confirmed | no restriction recorded | editorial ruling (no clause cited) |
| milaEnglish | transliteration | matched automatically | no restriction recorded | editorial ruling (no clause cited); Note: Pinyin / Chinese trade name. |
How each authority words this name: see Names › Authority wording.
- GSJ (Japan) formal name
- 不透明琥珀（中国市場名「蜜蝋／ミーラー」） (not yet checked for this body — the entry's own Japanese name is shown)
- Chinese formal name
- 蜜蜡 (GB/T 16552—2017 Table A.3)
- Mineralogical name
- Opaque amber; a Chinese colour/transparency trade category, not a separate mineral or a synonym for Baltic amber
- Trade names and synonyms
- mila (transliteration) · butterscotch amber (market name; conditional name)
Four-language names
- 简体中文
- 蜜蜡
- 繁體中文
- 蜜蠟
- English
- Opaque Amber (Chinese trade name: mila)
- 日本語
- 不透明琥珀（中国市場名「蜜蝋／ミーラー」）
Qualifiers stripped from the headline name
See also: Misleading and prohibited trade names · Supplementary name index
Classification
- Origin
- Natural materials
- Material domain
- Natural organic and biogenic materials
- Browsing family
- Amber and natural resin 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
The treatment classification for Opaque Amber is applied by this site from the Amber row of GB/T 16552—2017 Annex B, Table B.1; the standard's table registers amber and has no separate entry for Opaque Amber. On that basis, heating is listed as optimization; filling and coating are classed by graded definitions, explained on this site's Gem treatments page; and irradiation, colour change by heating under pressure, and dyeing are all listed as treatment. The full effect column for each treatment is on the Amber entry, and the notes to Table B.1 and the graded definitions are on the Gem treatments page.
GB/T 16552-2017, Annex B, Table B.1
Under the “Amber” row of Table B.1: Heating Optimization; Filling Graded — see §5.4.1, Table 1; Coating Graded — see §5.4.1, Table 1; Irradiation Treatment; Colour change by heating under pressure Treatment; Dyeing Treatment. The full row, with the effect column, is on the Amber 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
Opaque Amber is amber whose transparency ranges from translucent to opaque. Mohs hardness is 2–2.5; this site notes that the cited clause covers the whole amber species, Opaque Amber being only one variety within it. Also given for amber (the whole class): the structure (overall) is amorphous, there is no cleavage, density is 0.96–1.1 g/cm³ (this site notes that the range is derived from the clause value of 1.08 with a tolerance of +0.02/−0.12), and it becomes electrically charged when rubbed. The optical items are likewise given for amber (the whole class): the optic character is isotropic, with strain often causing anomalous extinction and interference colours in amber; refractive index is 1.54, which this site notes is a reading commonly obtained by the spot method, a typical value rather than an absolute limit, and the clause has further sub-grades, with the overall value registered; there is no birefringence; when untreated, there is no pleochroism and the lustre is resinous.
Registered material facts
Each row carries its own source and check date and can be cited on its own; “—” means the cited source gives no value, not “none”.
Chemical composition, long-wave UV luminescence, short-wave UV luminescence, UV-visible spectrum, infrared spectrum, magnification: these whole-class features are given in the cited clause for amber (whole class), so they are not repeated on the Opaque Amber page; see the material facts on the Amber entry.
Items below that name the class they cover give the cited clause’s value for that whole class, not a measurement of Opaque Amber (how to read class-level values).
Definition
Opaque Amber: amber ranging from translucent to opaque
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): §5.3.5 Additional notes (locator checked 2026-09-28)
- Fact checked on
- 2026-09-21
Structure
Opaque Amber — structure (overall): amorphous (not crystalline)
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- amber (whole class)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.3.5 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Durability
Opaque Amber — Mohs hardness: 2–2.5
GIA Gem Encyclopedia
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))
- 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 — Amber (Gemological Institute of America): Section “FACTS”, “Mohs Hardness” (locator checked 2026-09-28)
- Fact checked on
- 2026-09-20
Opaque Amber — cleavage: none
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- amber (whole class)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.3.5 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
stability2 sources compared
Opaque Amber — stability: low hardness, so it scratches easily; chips and cracks easily; dissolves on contact with solvents such as nail varnish remover, so keep it away from all solvents and other strong chemicals; no ultrasonic cleaning; pieces with superficial colour or surface layers are not suitable for re-cutting or re-polishing.
CIBJO Gemstone Book 2022
CIBJO Gemstone Book §6.2:special-care code a, special-care code b, special-care code i, special-care code j, special-care code m
- Treatment state
- untreated
- Qualification
The row we cite covers amber as a whole, and this entry is one of its varieties. The row states a property that holds for every piece alike — whether it dissolves, whether it cracks. That kind of property carries over to this entry. A numeric range such as hardness would not.
Source & check 2026-09-25
- Source
- CIBJO Blue Book — Official Gemstone Book (Coloured Stone Commission 2022) (CIBJO): §8 Annex C, Amber, p.32; §6.2 a, b, i, j, m (locator checked 2026-09-21)
- Fact checked on
- 2026-09-25
Opaque Amber — stability: may melt on contact with a hot needle, giving off an aromatic smell.
GB/T 16553—2017
- Treatment state
- untreated
- Does this standard apply
- applies to this entry
- What this covers
- amber (whole class)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.3.5 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Physical properties
Opaque Amber — density: 0.96–1.1 g/cm³
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- amber (whole class)
- Qualification
The clause we cite gives 1.08, with a stated tolerance of +0.02 / -0.12. The range shown here is worked out from that.
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.3.5 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Opaque Amber — triboelectricity: may become electrically charged when rubbed
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- amber (whole class)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.3.5 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Optical
Opaque Amber — optic character: isotropic, but stress often gives anomalous extinction along with interference colours.
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- amber (whole class)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.3.5 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Opaque Amber — refractive index: 1.54
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- amber (whole class)
- 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.
- General note
- the clause has finer ranges
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.3.5 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Opaque Amber — birefringence: none
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- amber (whole class)
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.3.5 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Opaque Amber — pleochroism: none
GB/T 16553—2017
- Treatment state
- untreated
- Does this standard apply
- applies to this entry
- What this covers
- amber (whole class)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.3.5 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Quality factors
Opaque Amber — quality factor (lustre): resinous
GB/T 16553—2017
- Treatment state
- untreated
- Does this standard apply
- applies to this entry
- What this covers
- amber (whole class)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.3.5 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Each row's “Source & check” expands to the full source; the date beside it is the fact check date.
This material (RI / SG midpoints): 1.54 / 1.03; Closest values: 1Turtle Shell 1.545 / 1.31, 2Plastic 1.58 / 1.3, 3Jet 1.66 / 1.32, 4Black Coral 1.565 / 1.71, 5Mammoth Ivory 1.53 / 1.75
Show the full chart (330 registered materials)
Outside the full chart's range, drawn as triangles at the edge (RI / SG midpoints): Hematite 3.045/5.12, Synthetic Rutile 2.76/4.26, Rutile 2.753/4.23, Synthetic Moissanite 2.67/3.22
Testing and market
The CIBJO laboratory protocol covers Opaque Amber under “Amber” (§6.2.1): see identification on the Amber entry; the required tests are listed on the CIBJO laboratory protocol table for Amber.
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
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.
- GIA – Gemological Institute of America (United States). Gem Encyclopedia: Amber Description.
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 Amber on this site: 10 entries listed by this site's parent-entry links; synthetic, treated and similar entries carry their recorded state after the name; this page (Opaque Amber) is marked.
This table scrolls sideways on narrow screens.
| Page | Content | Status |
|---|---|---|
| Browsing family | Amber and natural resin materials | Live |
| Treatments recorded for this material | Heated / Heat-treated (via parent material), Filled / Fracture-filled (via parent material), Coated (via parent material), Irradiated (via parent material), Dyed (via parent material) | Live |
| Related articles | To be added (placeholder) | Planned |
Who maintains this page
The material facts in the Opaque Amber 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.