AGTA Enhancement Code B: Bleaching
AGTA Enhancement Code B: Bleaching
The industry-standard disclosure designation for chemical bleaching of gemstones and pearls
Within the American Gem Trade Association's gemstone enhancement disclosure system, Code B designates bleaching — the deliberate application of chemical agents to lighten, even, or entirely remove colour from a gemstone or organic gem material. The code forms part of a standardised disclosure framework that AGTA requires of its members when offering treated stones in commerce, ensuring that buyers, retailers, and laboratories share a common vocabulary for describing what has been done to a gem after it leaves the earth. Code B is among the most frequently encountered enhancement designations in the pearl and jadeite trades, and understanding its scope, chemistry, and market implications is essential for anyone working with those materials professionally.
The AGTA Enhancement Disclosure System
AGTA introduced its lettered enhancement code system to bring transparency and consistency to a trade in which the word "treated" had long been applied inconsistently. Each letter in the system corresponds to a specific category of enhancement: Code H covers heating, Code F fracture filling, Code I impregnation with polymers or resins, Code R irradiation, and so on. Code B — standing for bleaching — sits alongside these as one of the foundational categories. AGTA guidelines require member firms to disclose all known treatments at the point of sale, and the codes provide the shorthand through which that disclosure is communicated on invoices, laboratory reports, and auction catalogues. The system has been widely adopted beyond AGTA's own membership and is referenced by major gemmological laboratories including the Gemological Institute of America when characterising enhancement status on grading reports.
Chemistry and Mechanism
Bleaching in the gemmological context refers to oxidative or reductive chemical processes that break down or dissolve chromophoric compounds — the molecules responsible for undesirable colour — within a gem material. The most commonly employed agent is hydrogen peroxide (H₂O₂), typically used in concentrations ranging from dilute aqueous solutions to more concentrated preparations, sometimes in combination with heat or ultraviolet light to accelerate the reaction. Chlorine-based compounds, including sodium hypochlorite, are also used in certain applications, particularly in the pearl trade.
The mechanism differs depending on the substrate. In organic materials such as nacre, the bleaching agent oxidises pigment molecules — principally porphyrins and carotenoids — that contribute yellowish or brownish tones. In jadeite, bleaching targets iron-oxide staining concentrated in surface-reaching fractures and along grain boundaries, converting or dissolving the ferric compounds responsible for brown or rusty discolouration. The result in both cases is a lighter, more uniformly coloured material that presents more attractively in the marketplace.
Bleaching of Cultured Pearls
Virtually all commercially traded cultured pearls undergo some degree of bleaching as a routine post-harvest processing step. Freshwater cultured pearls in particular are commonly bleached to achieve the bright, uniform white that the mass market expects. Akoya cultured pearls are similarly treated, with bleaching often followed by a mild pinking or overtone-enhancement step. The process is carried out by immersing harvested pearls in hydrogen peroxide solutions, sometimes under controlled light exposure, for periods ranging from hours to several days depending on the desired degree of lightening.
Because bleaching of pearls is so universal, AGTA and the broader trade treat it as an assumed baseline rather than a noteworthy exception — analogous to the way cutting and polishing are not separately disclosed. Nevertheless, Code B remains the correct formal designation when explicit disclosure is required, as on a laboratory report or a high-value auction listing. The treatment is considered permanent and stable under normal wearing conditions; the nacre itself is not structurally compromised by properly conducted bleaching, and the resulting colour is not expected to revert.
Bleaching of Jadeite
It is in the jadeite trade that Code B carries its most consequential implications. Natural jadeite rough frequently contains brown or yellowish staining caused by oxidised iron compounds that have migrated into the stone along fracture networks over geological time. Bleaching — immersion in acid solutions (commonly oxalic acid or dilute hydrochloric acid) rather than hydrogen peroxide alone — dissolves this staining and can dramatically improve the apparent colour and translucency of the material. The resulting stone is cleaner in appearance but is also structurally altered: the dissolution of staining material leaves behind a network of micro-voids and weakened grain boundaries.
Because bleached jadeite in this condition is fragile and prone to surface crazing, it is almost invariably followed by polymer impregnation — AGTA Code I — in which an epoxy resin or similar compound is introduced under vacuum or pressure to fill the voids, restore structural integrity, and improve translucency. The combination of these two treatments produces what the trade designates as B+I jade, or colloquially Type B jade (as distinct from untreated Type A jade and dyed Type C jade). This terminology, while not formally part of the AGTA lettered system, is universally understood in the jadeite trade and is used by laboratories in Hong Kong, mainland China, and internationally.
The distinction between Type A and Type B jadeite is commercially significant. Fine untreated jadeite — particularly the vivid, highly translucent material known as imperial jade — commands prices that can reach hundreds of thousands of dollars per carat for exceptional pieces. Type B material, regardless of its surface appearance, is valued far more modestly, and misrepresentation of treatment status constitutes fraud in most jurisdictions. Major gemmological laboratories including GIA, the Gemmological Association of All China (GAC), and the Hong Kong Jade and Stone Laboratory routinely test for polymer impregnation using Fourier-transform infrared spectroscopy (FTIR), which detects the characteristic absorption bands of organic resins absent from untreated jadeite.
Stability and Durability Considerations
For pearls, Code B bleaching is regarded as stable under normal conditions of wear, storage, and cleaning. Pearls should not be exposed to harsh chemicals or ultrasonic cleaning regardless of treatment status, but bleaching per se does not introduce additional fragility. For jadeite treated with bleaching alone (without subsequent impregnation — a relatively rare commercial scenario), the micro-void network left by acid treatment renders the stone susceptible to cracking and surface deterioration; such material is not considered suitable for jewellery use without further stabilisation. In the B+I combination, the polymer fill provides mechanical support, but the resin is subject to yellowing with age and ultraviolet exposure, and can be damaged by heat, solvents, and ultrasonic cleaning — all of which must be disclosed to purchasers and avoided by jewellers working with the material.
Disclosure Requirements and Trade Practice
AGTA guidelines mandate that member firms disclose Code B treatment — and any combination of codes, such as B+I — at every stage of the commercial chain, from wholesaler to retailer to end consumer. The disclosure must be made in writing on invoices and sales documents. Failure to disclose a known treatment is a violation of AGTA's Code of Ethics and may also constitute a breach of consumer protection legislation in many jurisdictions.
In practice, the disclosure landscape for pearls is complicated by the near-universal nature of bleaching in that trade. Industry consensus, reflected in guidance from AGTA and the International Colored Gemstone Association (ICA), generally holds that routine, universally applied pearl processing steps need not be individually itemised provided that the buyer understands the baseline. For jadeite, however, the commercial stakes are high enough that explicit disclosure of B+I status is non-negotiable in reputable trade, and laboratory certification from a recognised testing house is considered essential for any significant transaction.
Identification
Gemmological identification of Code B bleaching varies by material. In pearls, bleaching is difficult to detect definitively by standard gemmological testing; the treatment leaves no reliable spectroscopic signature, and its universal application makes the question largely moot in routine trade. In jadeite, bleaching is most reliably identified in conjunction with polymer impregnation through FTIR spectroscopy, which reveals resin absorption bands, and through careful examination under magnification, which may reveal surface crazing, an unnaturally clean fracture network, or a slightly waxy surface lustre inconsistent with natural polish. Specific gravity measurement may also be informative, as resin-filled jadeite tends to show slightly lower density than untreated material, though this is not a definitive test in isolation.