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UnderstandWhat it is, what people ask, how far this page goes
Natural inorganic gem materials · Trade name: colour / appearance variety · Natural identity; treatment status unknown
Perthite
A name for the striped intergrowth structure inside potassium feldspar, not a separate mineral species; names such as "green perthite" are common on the market. 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 Perthite forms and what gives its colourFormation setting, process and timescale; where its colour and optical effects come from, each finding graded and sourced
- Treatments and enhancements of PerthiteThe enhancements and treatments the GB/T and JJA/AGL tables list
- Hardness, density and refractive index of PerthiteEach value with its source and check date
- Perthite 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 PerthiteThe 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
Perthite is not a mineral species but a texture/intergrowth: a potassium feldspar host (orthoclase, microcline, etc.) containing oriented lamellae of sodium-rich feldspar (albite) that exsolved from the solid solution, the two forming a layered intergrowth. Its mechanism is solid-state exsolution: a homogeneous alkali feldspar solid solution becomes unstable on slow cooling and unmixes into two or more separated phases; because the exsolved phases have similar crystal structures, the intergrowth is commonly lamellar, sometimes periodic or quasiperiodic, i.e. exsolution lamellae. When these lamellae are submicron and nonperiodic the texture is cryptoperthite, the structure that produces moonstone’s ‘moonlight’ glow — white light interfering at the alternating lamellar interfaces to give structural colour.
Scope: Covers the exsolution-intergrowth nature of perthite/cryptoperthite and its connection with the optical effect of moonstone; does not apply to feldspars that appear layered only because of twinning or inclusions.
Sources G&G Summer 2025 · G&G Winter 2017
Where it forms
Alkali feldspars in slowly cooled igneous rocks (plutonic rocks, pegmatites) where the solid solution can exsolve.
Sources G&G Summer 2025
Potassium feldspars recrystallised or slowly cooled in metamorphic rocks may also develop exsolution-lamellae intergrowths.
Sources G&G Summer 2025
How it forms, step by step
At high temperature the albite and orthoclase components coexist as a homogeneous solid solution in one crystal.
On slow cooling the solid solution becomes unstable and unmixes into two or more separated phases (exsolution).
Because the exsolved phases have similar structures, the product is commonly lamellar, sometimes periodic or quasiperiodic — the exsolution lamellae that give the perthite texture.
When the lamellae are submicron and nonperiodic the texture is cryptoperthite, and white light interfering at the alternating lamellae produces moonstone’s adularescence.
Link to appearance
Coarse exsolution lamellae are visible as oriented albite bands within the potassic host (perthite), while submicron nonperiodic lamellae (cryptoperthite) manifest as the blue adularescence of moonstone.
Sources G&G Summer 2025
Timescale
The sources give no absolute age or duration for the perthite exsolution texture, only that it forms on slow cooling.
Sources G&G Summer 2025 · G&G Winter 2017
Related base materials
- Alkali feldspar: Perthite is a replacement/exsolution intergrowth texture of alkali feldspar (potassium feldspar host plus exsolved albite), not a separate mineral
Supporting findings
Perthite’s layered intergrowth forms by solid-state exsolution: a homogeneous solid solution unmixes on cooling into two or more phases, and when the phases have similar structures the product is commonly lamellar, sometimes periodic or quasiperiodic exsolution lamellae.
Evidence grade AScope: The general definition of exsolution; it is driven by temperature/pressure change (some authors also include change in oxidation state).
The albite lamellae exsolved from a potassic feldspar matrix can be crosscut by later iron oxide films (e.g. magnetite/hematite), showing the exsolution texture predates the iron precipitation.
Evidence grade AScope: Illustrated by Australian rainbow lattice sunstone (plagioclase lamellae exsolved from orthoclase); other localities may be similar.
Recorded localities
Authoritative sources list the localities below; the list is not exhaustive.
Seas and coasts
- Worldwideperthite is an exsolution intergrowth that occurs widely in alkali feldspars
Sources Handbook of Mineralogy · Smith College lecture notes
These are localities recorded by authoritative sources, not an origin finding for any individual piece. The CIBJO Gemstone Book (2022, §4.2.3) says a place of origin names where a gem was mined or harvested, is a matter of opinion, does not imply a level of quality, and that cutting, processing or exporting centres must not be used to imply origin. See the origin determination guide and the overview of recorded localities.
Causes of colour and optical effects
Cryptoperthite — an alkali feldspar with nonperiodic submicron intergrown albite–orthoclase textures — is the structure that can produce moonstone’s desaturated iridescence and be strictly called ‘moonstone’.
Evidence grade AScope: Applies to alkali feldspars with cryptoperthite texture; coarse perthite generally shows no such iridescence.
Other research findings
Perthite is not a mineral species but a layered intergrowth (texture) of a potassium feldspar host with exsolved sodium-rich (albite) lamellae.
Evidence grade AScope: A texture name, not a species; its constituents are the potassic and sodic feldspar phases.
Limits of this research
- Research status: Formation, occurrence or other material-specific findings found in authoritative sources
- The authority text does not define or describe perthite as a separate entry; this record generalises from its account of solid-state exsolution and moonstone structure.
- No absolute age or duration for the exsolution texture is given.
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
- Perthite
GB/T 16552—2017 5.1.1 b)
Construction or treatment status
Natural identity; treatment status unknown
Treatments recorded for this material: Filled / Fracture-filled (via parent material), Coated (via parent material), Diffusion-treated (via parent material), Irradiated (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
"Perthite" is a market name rather than a mineral species name; before using it, verify: Industry-wide term that does not denote a single species.
What this means for you
Before buying, check the recommended listing name "Perthite" 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
- Industry-wide term that does not denote a single species.
- Suggested listing name
- Perthite
Care and wear
No care facts are recorded for this entry itself. Its parent material has care records: see Feldspar.
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 | — | — |
| Coating | — | — | Treatment | — | — |
| Diffusion | — | — | Treatment | — | — |
| Irradiation | — | — | Treatment | — | — |
“—” means the cited source gives no value for that item, not “none”. Source: GB/T 16552—2017 Table B.1 (row for Feldspar)
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
VerifyNames, standards, technical facts, clauses and sources
Names
Besides Perthite, the name register records "Perthite", for which no restriction on use as a name is recorded.
Standard and listing namesPerthite is not listed in the GB/T 16552—2017 text, and its GB/T naming counterpart is Feldspar (GB/T 16552—2017 Table A.1); the mineralogical name describes an intergrowth texture in potassium feldspar, not a separate mineral species, and the trade name or synonym is Perthite. The suggested listing name is Perthite, and the market often uses names such as “green perthite”. Names in four languagesThe names are given in Simplified Chinese, Traditional Chinese, English (Perthite) and Japanese (a transliteration). Institution usageAmong authority wordings, the FTC and CIBJO source texts have no wording for this name (checked), and GIA and Gem-A have not been checked; bodies without a recorded wording show Perthite's own English name, Perthite, which does not represent their position. Japanese namesThe Japanese GSJ formal wording is not yet verified by this site, and Perthite's own Japanese name is a transliteration.
Name register
Every name recorded for this entry, with how it is classified, whether it may be matched to this entry automatically, whether it may be used as a product name, and the clause it rests on.
This table scrolls sideways on narrow screens.
| Name | Type | Matching | Use as a name | Basis |
|---|---|---|---|---|
| no restriction recorded (1) | ||||
| PerthiteEnglish | synonym | matched automatically | no restriction recorded | editorial ruling (no clause cited) |
How each authority words this name: see Names › Authority wording.
- GSJ (Japan) formal name
- パーサイト (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)
- 长石 (GB/T 16552—2017 Table A.1)
- Mineralogical name
- Intergrowth texture of potassium feldspars, not a mineral species
Four-language names
- 简体中文
- 条纹长石
- 繁體中文
- 條紋長石
- English
- Perthite
- 日本語
- パーサイト
See also: Misleading and prohibited trade names · Supplementary name index
Classification
- Origin
- Natural materials
- Material domain
- Natural inorganic gem materials
- Browsing family
- Feldspar materials
- Identity tier
- Trade name: colour / appearance variety
- Mineral chemical class
- Silicates
- Construction or treatment status
- Natural identity; treatment status unknown
Treatments listed by standards
For Perthite, this site applies the Feldspar row of GB/T 16552—2017 Annex B, Table B.1: filling is handled by the grades set out in the standard, and coating, diffusion and irradiation are all classed as treatment. The notes to Table B.1 and the definitions of each grade are on this site's Gem treatments page, and the Feldspar row with the effect column is on the Feldspar entry.
GB/T 16552-2017, Annex B, Table B.1
Under the “Feldspar” row of Table B.1: Filling Graded — see §5.4.1, Table 1; Coating Treatment; Diffusion Treatment; Irradiation Treatment. The full row, with the effect column, is on the Feldspar 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
Apart from chemical composition, fluorescence, UV-visible spectrum, infrared spectrum and magnification, which are in the material facts of the Feldspar entry, all material facts for Perthite are taken from the cited GB/T 16553—2017 clauses for feldspar (the whole mineral group), not measured on Perthite separately. For feldspar (the whole mineral group), the structure is crystalline, with a tabular or short prismatic crystal habit and common Carlsbad, polysynthetic and cross-hatched twinning; as for crystal system, moonstone and amazonite are monoclinic or triclinic, while sunstone and labradorite are triclinic; Mohs hardness is 6–6.5, with two directions of perfect cleavage. For feldspar (the whole mineral group), density 2.55–2.75 g/cm³, refractive index 1.508–1.572 and birefringence 0.005–0.01 are all registered as the overall values of the clause sub-grades; the optic character is anisotropic, biaxial positive or negative; when untreated, there is usually no pleochroism and the lustre is vitreous; iridescence, the cat's-eye effect, asterism and aventurescence can all be seen.
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 feldspar (the whole mineral group), so they are not repeated on the Perthite page; see the material facts on the Feldspar entry.
Items below that name the class they cover give the cited clause’s value for that whole class, not a measurement of Perthite (how to read class-level values).
Structure
Perthite — structure (overall): crystalline
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- feldspar (the whole mineral group)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.17 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Perthite — structure (crystal system): Moonstone and amazonite belong to the monoclinic or triclinic system; sunstone and labradorite are triclinic.
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- feldspar (the whole mineral group)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.17 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Perthite — structure (crystal habit): Crystals are tabular or stubby prisms; Carlsbad, polysynthetic and gridiron (cross-hatched) twinning are common.
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- feldspar (the whole mineral group)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.17 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Durability
Perthite — Mohs hardness: 6–6.5
GB/T 16553—2017
Reference points on this site: Talc 1–3, Fluorite 4, Apatite 5–5.5, Orthoclase 6–6.5, Topaz 8, Diamond 10 (Source: GB/T 16553—2017); Gypsum 1.5–2, Calcite 3, Quartz 7 (Source: Handbook of Mineralogy); Corundum 9 (Source: GIA Gem Encyclopedia (care guide))
- Does this standard apply
- applies to this entry
- What this covers
- feldspar (the whole mineral group)
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.17 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Perthite — cleavage: two directions of perfect cleavage
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- feldspar (the whole mineral group)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.17 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Physical properties
Perthite — density: 2.55–2.75 g/cm³
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- feldspar (the whole mineral group)
- General note
- the clause has finer ranges
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.17 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Optical
Perthite — optic character: biaxial and anisotropic; optic sign may be either positive or negative.
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- feldspar (the whole mineral group)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.17 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Perthite — refractive index: 1.508–1.572
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- feldspar (the whole mineral group)
- General note
- the clause has finer ranges
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.17 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Perthite — birefringence: 0.005–0.01
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- feldspar (the whole mineral group)
- General note
- the clause has finer ranges
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.17 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Perthite — pleochroism: usually absent
GB/T 16553—2017
- Treatment state
- untreated
- Does this standard apply
- applies to this entry
- What this covers
- feldspar (the whole mineral group)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.17 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Perthite — optical effect (iridescence): seen
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- feldspar (the whole mineral group)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.17 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Perthite — optical effect (chatoyancy): seen
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- feldspar (the whole mineral group)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.17 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Perthite — optical effect (asterism): seen
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- feldspar (the whole mineral group)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.17 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Perthite — optical effect (aventurescence): seen
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- feldspar (the whole mineral group)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.17 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
- CIBJO definitions
- chatoyancy, asterism, aventurescence
Quality factors
Perthite — quality factor (lustre): vitreous
GB/T 16553—2017
- Treatment state
- untreated
- Does this standard apply
- applies to this entry
- What this covers
- feldspar (the whole mineral group)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.17 (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 / 2.65; Closest values: 1Charoite 1.554 / 2.66, 2Changhua Stone 1.56 / 2.6, 3Shoushan Stone 1.56 / 2.7, 4Balin Stone 1.56 / 2.55, 5Bamboo Coral 1.57 / 2.65
Show the full chart (330 registered materials)
Outside the full chart's range, drawn as triangles at the edge (RI / SG midpoints): Hematite 3.045/5.12, Synthetic Rutile 2.76/4.26, Rutile 2.753/4.23, Synthetic Moissanite 2.67/3.22
Evidence and sources
Authority basis and clause sources
Sources
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 Feldspar on this site: 13 entries listed by this site's parent-entry links; synthetic, treated and similar entries carry their recorded state after the name; this page (Perthite) is marked.
This table scrolls sideways on narrow screens.
| Page | Content | Status |
|---|---|---|
| Browsing family | Feldspar materials | Live |
| Treatments recorded for this material | Filled / Fracture-filled (via parent material), Coated (via parent material), Diffusion-treated (via parent material), Irradiated (via parent material) | Live |
| Related articles | To be added (placeholder) | Planned |
Who maintains this page
The material facts in the Perthite 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.