On this page
UnderstandWhat it is, what people ask, how far this page goes
Natural inorganic gem materials · Mineral / gemstone variety · Natural identity; treatment status unknown
Hydrophane Opal
A highly porous opal that can absorb liquids and change in appearance. It can take up dye, sugar solution or resin, and any treatment must be disclosed. 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 Hydrophane Opal forms and what gives its colourFormation setting, process and timescale; where its colour and optical effects come from, each finding graded and sourced
- How to identify Hydrophane OpalIdentification points from the research literature; how far lab testing can go
- Treatments and enhancements of Hydrophane OpalThe enhancements and treatments the GB/T and JJA/AGL tables list
- Caring for and wearing Hydrophane OpalCleaning, heat, chemicals and light, as the cited sources give them
- Hardness, density and refractive index of Hydrophane OpalEach value with its source and check date
- Hydrophane Opal 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 Hydrophane OpalThe listing name to use; what must be disclosed before sale; how lab reports word it
- Standard clauses that define Hydrophane OpalWhich 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
Hydrophane opal is opal of high porosity that takes up liquids and changes appearance as a result; the substance remains opal. In a GIA study of Ethiopian hydrophane opal, slices gained weight noticeably and became more transparent while soaked in water, with specific gravity of about 1.93 ±0.03; because porosity is uneven, the uptake varied through each piece, amounting to roughly 5–13% weight change in water, and about a week was needed for the original weight and appearance to return. Such high porosity also permits filling with oil or Opticon: oil raised transparency yet destroyed play-of-color, whereas Opticon raised transparency while keeping play-of-color; the source notes that the process may be combined with other treatments—for instance dyeing or a sugar-acid treatment—in order to raise the material's durability and transparency. A purple opal said to come from a new deposit proved, on gemological and spectroscopic evidence, to be artificially coloured—in fact dyed hydrophane opal from Wollo Province, Ethiopia.
Scope: Used to describe natural opal of high porosity whose weight and appearance change after absorbing liquid and which can take filling/dyeing treatment; hydrophane opal is a property/variety of opal, not a separate mineral.
Sources G&G Spring 2016 · G&G Winter 2011
Where it forms
Volcanic or volcaniclastic host rock (e.g. Wollo, Ethiopia): highly porous opal forms in such host environments.
Sources G&G Spring 2016
How it forms, step by step
The opal has non-uniform porosity, which provides the physical basis for its water-absorbing ability.
Sources G&G Spring 2016
When immersed in water, water enters the pores; the material shows obvious weight gain and improved transparency, and its appearance changes.
Sources G&G Spring 2016
After removal from water, it takes about one week to restore the original weight and appearance.
Sources G&G Spring 2016
The high porosity allows the hydrophane opal to be filled with oil or Opticon, and can be combined with dyeing or sugar-acid treatment (artificial treatments).
Sources G&G Spring 2016
Link to appearance
When dry it appears whitish/cloudy to brownish and semitransparent to translucent; after absorbing water it gains weight, becomes more transparent and its color deepens or changes, reverting over about a week.
Sources G&G Spring 2016
Timescale
The sources give the duration of water uptake and recovery (transparency improved after about 20–30 minutes of immersion; about one week to restore), but no geologic age or absolute timescale for the formation of hydrophane opal.
Sources G&G Spring 2016
Related base materials
- Opal (hydrated amorphous silica): variety-of | Hydrophane opal is a highly porous opal that can absorb water and change in appearance; the material itself is still opal
Recorded localities
Authoritative sources list the localities below; the list is not exhaustive.
Africa
- Wegel Tena, Wollo, Ethiopia
Sources Gems & Gemology Summer 2010 · G&G Winter 2011
Europe
- Červenica-Dubník, SlovakiaListed among varieties sorted at the site, not as its main product.
Sources G&G Winter 2023
North America
- Virgin Valley, Nevada, United States
Sources Mindat: Opal
- Opal Butte, Oregon, United States
Sources Mindat: Opal
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.
Causes of colour and optical effects
Hydrophane opal produces play-of-color through the same mechanism as precious opal—an ordered array of nanoscale silica spheres acting as a diffraction grating—but is distinguished by high, non-uniform porosity: in the dry state it looks whitish, cloudy, and less transparent, while absorbed water fills the pores, transparency rises, and the look changes as water content rises and falls.
Evidence grade AScope: The mechanism addresses the diffraction origin of hydrophane opal's play-of-color and the porosity-related changes in its appearance; it does not establish locality, natural origin, or treatment of any particular stone.
Filling treatments alter the optics of hydrophane opal: an oil fill raises transparency but destroys play-of-color, whereas an Opticon fill raises transparency while keeping it, indicating that the flashes depend on the grating of silica spheres remaining intact; such treatment is hard to see by eye or under the microscope yet detectable instrumentally.
Evidence grade AScope: The conclusion comes from laboratory treatment experiments on samples; whether a stone has been filled must be confirmed by a gem laboratory, and it does not establish locality or natural origin of any particular sample.
Sources G&G Spring 2016
How it is identified
Because hydrophane opal is porous and absorbs water, its look changes with its moisture state, making the eye especially unreliable. Deciding whether a specimen is natural, treated or imitation/composite material calls for laboratory measurement of gemological properties and composition. The conclusion should be issued by a qualified gem laboratory and cannot be decided from appearance.
Evidence grade AScope: Applies where natural, treated and imitation opal must be distinguished; no self-administered criteria are given.
Other research findings
Hydrophane opal gains weight and transparency when it absorbs water; its water-absorbing ability comes from non-uniform porosity, amounts to about 5% to 13% weight change in water, and takes about one week to restore.
Evidence grade AScope: Data are from experiments on slices cut from one ~4 cm piece of Ethiopian hydrophane opal; values may differ for other material.
Sources G&G Spring 2016
Hydrophane opal may be filled with oil or with Opticon. With oil, transparency improves but play-of-color is lost; with Opticon, transparency improves and play-of-color survives, and the treatment can be paired with others such as dyeing or a sugar-acid treatment.
Evidence grade AScope: These are laboratory treatment-experiment results on samples; whether a given stone is treated must be confirmed by a gem laboratory.
Sources G&G Spring 2016
Purple opal seen in the market was shown by gemological and spectroscopic evidence to be artificially colored—actually dyed hydrophane opal from Ethiopia's Wollo Province.
Evidence grade AScope: Concerns that batch of purple opal reportedly from a new Mexican deposit; does not apply to all purple opal or all hydrophane opal.
Sources G&G Winter 2011
The water-absorbing ability of hydrophane opal is not uniform through a piece, resulting from its non-uniform porosity.
Evidence grade AScope: An observation from comparing slice-by-slice measurements within one piece of rough.
Sources G&G Spring 2016
Limits of this research
- Research status: Formation, occurrence or other material-specific findings found in authoritative sources
- Hydrophane is a property/variety of opal; the material is opal, not an independent mineral.
- Values such as 5%–13% weight gain and SG 1.93±0.03 come from experiments on one piece of Ethiopian hydrophane opal and cannot be generalized to all hydrophane opal.
- The sources give no geologic age or absolute timescale for the formation of hydrophane opal.
- Whether a treatment (oil/Opticon/dyeing/sugar-acid) has been applied must be confirmed by a gem laboratory.
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
- Hydrophane Opal (treatments must be disclosed)
IMA Mineral List 2026-07 “Opal” · CIBJO Gemmological Laboratories Book 2024 §7.2.1.112 “Hydrophane”
Construction or treatment status
Natural identity; treatment status unknown
Treatments recorded for this material: Filled / Fracture-filled (via parent material), Dyed (via parent material), Coated (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
Hydrophane Opal is Porous opal that can absorb liquids and change appearance; use "Hydrophane Opal (treatments must be disclosed)" for listings, and disclose any known treatments.
Evidence
- CIBJO · 7.2.1.112
What this means for you
Before buying, check the recommended listing name "Hydrophane Opal (treatments must be disclosed)" 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.
The item-by-item care advice that the GIA Care and Cleaning Guide gives for the whole class, and so for Hydrophane Opal, is set out in full under care on the Opal entry.
Care
Hydrophane Opal — care (chemicals): Treatments with dye, oil, resin, wax or plastic are not permanent; keep it away from all solvents (including dish-washing liquids), chemicals and heat.
CIBJO Gemstone Book 2022
CIBJO Gemstone Book §6.2:special-care code k
- Treatment state
- treated
Source & check 2026-09-26
- Source
- CIBJO Blue Book — Official Gemstone Book (Coloured Stone Commission 2022) (CIBJO): §8 Annex C, Hydrophane, p.64; §6.2 k (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Hydrophane Opal — care (special care): impregnated with colourless plastic: special care (SC); avoid heat.
AGTA Gemstone Information Manual, 17th ed.
- Treatment state
- treated
- Only after these treatments
- impregnation
Source & check 2026-09-26
- Source
- AGTA Gemstone Information Manual, 17th edition (August 2026) (AGTA): p.XII, Gemstone Information Chart, Opal Hydrophane I, CARE REQUIRED / SPECIAL ADVICE (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Hydrophane Opal — care (special care): dyed: special care (SC); keep away from fluids and oils.
AGTA Gemstone Information Manual, 17th ed.
- Treatment state
- treated
- Only after these treatments
- dyeing
Source & check 2026-09-26
- Source
- AGTA Gemstone Information Manual, 17th edition (August 2026) (AGTA): p.XII, Gemstone Information Chart, Opal Hydrophane D, CARE REQUIRED / SPECIAL ADVICE (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Hydrophane Opal — care (special care): impregnated with colourless oil, wax or resin to hide crazing: special care (SC).
AGTA Gemstone Information Manual, 17th ed.
- Treatment state
- treated
- Only after these treatments
- fissure filling with oil, fissure filling with resin
Source & check 2026-09-26
- Source
- AGTA Gemstone Information Manual, 17th edition (August 2026) (AGTA): p.XII, Gemstone Information Chart, Opal Hydrophane O, CARE REQUIRED / SPECIAL ADVICE (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
Care conclusions for Hydrophane Opal are given separately by treatment state and by the treatment concerned. CIBJOThe CIBJO Blue Book — Official Gemstone Book (Coloured Stone Commission 2022) states that for treated Hydrophane Opal the effects of dyeing, oiling, resin impregnation, waxing and plastic impregnation are not permanent, and it should be kept away from all solvents (including detergents of every kind), chemicals and heat. Special careThe 17th edition of the AGTA Gemstone Information Manual sets out special care requirements item by item for treated Hydrophane Opal; the cases needing special care (marked SC) are: impregnated only, that is, impregnated with colourless plastic, to be kept away from heat; dyed only, to be kept away from liquids and oils; and fracture-filled with oil or resin only, that is, impregnated with colourless oil, wax or resin to hide crazing. General careGeneral care for all gems, and the full table of CIBJO Gemstone Book special care letters, are in the general care part of the materials index page; the GIA care and cleaning guide is given for the whole class and so also applies to Hydrophane Opal, with each recommendation listed in full in the care part of the Opal entry.
This table scrolls sideways on narrow screens.
| Question | Matching entries |
|---|---|
| Contact with acids, alkalis and household chemicals | Treatments with dye, oil, resin, wax or plastic are not permanent; keep it away from all solvents (including dish-washing liquids), chemicals and heat |
Care entries by treatment state
The same entries grouped by the treatment state each applies to; each links to its full wording and source. Letters are CIBJO special-care codes, explained on the gemstone care page.
treated
treated (Only after these treatments: impregnation)
treated (Only after these treatments: dyeing)
treated (Only after these treatments: fissure filling with oil, fissure filling with resin)
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 |
|---|---|---|---|---|---|
| Filling | — | — | Graded — see §5.4.1, Table 1 | — | — |
| Dyeing | — | — | Treatment | — | — |
| Coating | — | — | Treatment | — | — |
“—” means the cited source gives no value for that item, not “none”. Source: GB/T 16552—2017 Table B.1 (row for Opal)
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
Hydrophane Opal — how lab reports word it (definition used on reports): On reports, hydrophane is opal that absorbs enough liquid to change its look and possibly its weight; since most opal is somewhat porous, the word is kept for markedly porous opal.
LMHC Information Sheet #13
Definition in the information sheet (original wording): opal that will absorb liquids to the point of affecting the appearance
- Case
- when the variety name may be used
Source & check 2026-09-26
- Source
- LMHC Information Sheet #13, Version 3, May 2025 (LMHC): p.1, “Definition” (Information Sheet #13) (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Hydrophane Opal — how lab reports word it (identification line): an optional line in the further-information part of the report (the sheet marks all wording in parentheses as optional).
LMHC Information Sheet #13
Wording on the report: may be called hydrophane opal in the trade
- Case
- when the variety name may be used
Source & check 2026-09-29
- Source
- LMHC Information Sheet #13, Version 3, May 2025 (LMHC): p.1, “Report wording” (Information Sheet #13) (locator checked 2026-09-26)
- Fact checked on
- 2026-09-29
Hydrophane Opal — how lab reports word it (durability note): a warning that it can soak up liquids, changing weight and appearance, so liquids should be avoided in wear and cleaning.
LMHC Information Sheet #13
Wording on the report: this gemstone may absorb liquids and as a result its weight and appearance may change
- Case
- all cases
Source & check 2026-09-26
- Source
- LMHC Information Sheet #13, Version 3, May 2025 (LMHC): p.1, “Report wording”, further information (Information Sheet #13) (locator checked 2026-09-28)
- Fact checked on
- 2026-09-26
Hydrophane Opal — how lab reports word it (suggested testing): One test is a water drop on the surface: if it soaks in within seconds, the opal counts as hydrophane. A soak-and-weigh test also exists but can crack the stone.
LMHC Information Sheet #13
Rule in the information sheet (original wording): If absorbed in few seconds, then considered hydrophane opal.
- Case
- all cases
Source & check 2026-09-26
- Source
- LMHC Information Sheet #13, Version 3, May 2025 (LMHC): p.1, “Suggested Testing Procedure” (Information Sheet #13) (locator checked 2026-09-28)
- Fact checked on
- 2026-09-26
VerifyNames, standards, technical facts, clauses and sources
Names
Names in four languagesHydrophane Opal has Simplified and Traditional Chinese names, the English name Hydrophane Opal and a Japanese name. Standard and listing namesThe Chinese standard naming counterpart is opal (GB/T 16552—2017 Table A.2), and the name Hydrophane Opal is not listed in the original. The suggested listing name is Hydrophane Opal (treatment disclosed). Institution usageOn authority wording, among GIA, FTC, CIBJO and Gem-A, the FTC and CIBJO texts on file have no wording for the name Hydrophane Opal (checked), and GIA and Gem-A wording is unchecked; bodies without a recorded wording show the entry's own English name, which does not represent their position. Japanese namesAs for Japan's GSJ, its wording for this name is not yet verified by this site, and the entry's own Japanese name is shown.
- GSJ (Japan) formal name
- ハイドロフェンオパール (not yet checked for this body — the entry's own Japanese name is shown)
- GB/T naming counterpart (this name is not in the standard)
- 欧泊 (GB/T 16552—2017 Table A.2)
- Mineralogical name
- Porous opal that can absorb liquids and change appearance
Four-language names
- 简体中文
- 吸水欧泊
- 繁體中文
- 吸水歐泊
- English
- Hydrophane Opal
- 日本語
- ハイドロフェンオパール
See also: Misleading and prohibited trade names · Supplementary name index
Classification
- Origin
- Natural materials
- Material domain
- Natural inorganic gem materials
- Browsing family
- Opal and natural amorphous silica materials
- Identity tier
- Mineral / gemstone variety
- Mineral chemical class
- Not applicable
- Construction or treatment status
- Natural identity; treatment status unknown
Treatments listed by standards
For Hydrophane Opal in GB/T 16552—2017 Annex B, Table B.1, this site applies the "Opal" row: filling is graded, dyeing is a treatment and coating is a treatment. 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 “Opal” row of Table B.1: Filling Graded — see §5.4.1, Table 1; Dyeing Treatment; Coating Treatment. The full row, with the effect column, is on the Opal 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, luminescence, UV-visible spectrum, infrared spectrum and magnification of Hydrophane Opal are registered for opal (the whole class) on the Opal entry. For opal (the whole class), the structure is amorphous, cleavage none, birefringence none, optic character isotropic, with fire opal often showing anomalous extinction, and among optical effects play of colour is visible and chatoyancy visible but rare. For opal (the whole class), density is 1.25–2.23 g/cm³, derived from the clause value of 2.15 with tolerances of +0.08 and −0.90; refractive index is 1.37–1.47, derived from the clause value of 1.450 with tolerances of +0.020 and −0.080, and, as this site's general notes explain, the clause has finer sub-ranges and the overall value is taken. Untreated, for opal (the whole class), pleochroism is none and lustre vitreous to resinous. The GIA Gem Encyclopedia registers a Mohs hardness of 5–6.5; this site's qualifying note says the cited source covers the whole species, of which Hydrophane Opal 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”.
Chemical composition, luminescence, UV-visible spectrum, infrared spectrum, magnification: these whole-class features are given in the cited clause for opal (whole class), so they are not repeated on the Hydrophane Opal page; see the material facts on the Opal entry.
Items below that name the class they cover give the cited clause’s value for that whole class, not a measurement of Hydrophane Opal (how to read class-level values).
Structure
Hydrophane Opal — structure (overall): amorphous (not crystalline)
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- opal (whole class)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.2.3 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Durability
Hydrophane Opal — Mohs hardness: 5–6.5
GIA Opal
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 — Opal (Gemological Institute of America): Section “FACTS”, “Mohs Hardness” (locator checked 2026-09-28)
- Fact checked on
- 2026-09-20
Hydrophane Opal — cleavage: none
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- opal (whole class)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.2.3 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Hydrophane Opal — stability: chips and cracks easily; porous, so keep it away from coloured liquids; will craze if it loses water, so keep it away from heat and dry air; avoid sudden temperature changes; no ultrasonic cleaning.
CIBJO Gemstone Book 2022
CIBJO Gemstone Book §6.2:special-care code b, special-care code c, special-care code d, special-care code e, special-care code j
- Treatment state
- untreated
Source & check 2026-09-21
- Source
- Fact checked on
- 2026-09-21
Physical properties
Hydrophane Opal — density: 1.25–2.23 g/cm³
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- opal (whole class)
- Qualification
The clause we cite gives 2.15, with a stated tolerance of +0.08 / -0.90. The range shown here is worked out from that.
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.2.3 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Optical
Hydrophane Opal — optic character: isotropic; fire opal commonly shows anomalous extinction.
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- opal (whole class)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.2.3 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Hydrophane Opal — refractive index: 1.37–1.47
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- opal (whole class)
- Qualification
The clause we cite gives 1.450, with a stated tolerance of +0.020 / -0.080. The range shown here is worked out from that.
- General note
- the clause has finer ranges
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.2.3 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Hydrophane Opal — birefringence: none
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- opal (whole class)
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.2.3 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Hydrophane Opal — pleochroism: none
GB/T 16553—2017
- Treatment state
- untreated
- Does this standard apply
- applies to this entry
- What this covers
- opal (whole class)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.2.3 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Hydrophane Opal — optical effect (play of colour): seen
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- opal (whole class)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.2.3 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Hydrophane Opal — optical effect (chatoyancy): seen; rare
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- opal (whole class)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.2.3 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
- CIBJO definitions
- play of colour, chatoyancy
Quality factors
Hydrophane Opal — quality factor (lustre): vitreous to resinous
GB/T 16553—2017
- Treatment state
- untreated
- Does this standard apply
- applies to this entry
- What this covers
- opal (whole class)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.2.3 (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): 1.42 / 1.74; Closest values: 1Synthetic Opal 1.45 / 2.08, 2Mammoth Ivory 1.53 / 1.75, 3Ivory 1.535 / 1.85, 4Hackmanite 1.483 / 2.27, 5Chrysocolla 1.516 / 2.2
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 Hydrophane Opal under “Opal” (§6.1.56): see identification on the Opal entry; the required tests are listed on the CIBJO laboratory protocol table for Opal.
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
Hydrophane Opal has a direct definition in the CIBJO Gemmological Laboratories Book 2024 under the term Hydrophane, listing the mineral species opal and the mineral or gemstone variety hydrophane; the CIBJO wording is quoted in full under Clause-level definitions on this page. The cross-check result is that it is defined directly by CIBJO, and no identically named English entry was found in this edition of the GB/T annex. Another registered term is Hydrophane Opal, based on GB/T 16552—2017 Annex A and defined as a porous opal that can absorb liquids and change in appearance; the cross-check result is that it is listed directly in GB/T, and no identically titled standalone entry was found in CIBJO.
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| Term | Clause | Definition | Cross-check |
|---|---|---|---|
| Hydrophane | 7.2.1.112 | Hydrophane is a variety of opal that will absorb liquids to the point of affecting the appearance and potentially the weight of the gemstone. Most opals have a porous structure to some extent, but when this porosity is considerable the term hydrophane may apply. Such opals could come from any opal locality. Opals from deposits in Ethiopia produce an unusually high percentage of such gemstones | Defined directly by CIBJO; no identically named English entry was found in this edition of the GB/T annex. |
| Hydrophane Opal | GB/T 16552-2017 Annex A | Porous opal that can absorb liquids and change appearance | 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.
- RRUFF Project, in partnership with the IMA – International Mineralogical Association. IMA Mineral List.
- Geological Survey of Japan, AIST (Japan). Museum mineral specimens, browse by classification.
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 Opal 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 (Hydrophane Opal) is marked.
- Opal
Sub-entries (16)
This table scrolls sideways on narrow screens.
| Page | Content | Status |
|---|---|---|
| Browsing family | Opal and natural amorphous silica materials | Live |
| Treatments recorded for this material | Filled / Fracture-filled (via parent material), Dyed (via parent material), Coated (via parent material) | Live |
| Related articles | To be added (placeholder) | Planned |
Who maintains this page
The material facts in the Hydrophane Opal 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.