HPHT non-disclosure refers to the practice — and the controversy surrounding it — of selling high-pressure high-temperature colour-treated diamonds without informing buyers that the stones had been subjected to a permanent, value-altering enhancement. The episode reached its crisis point in 1999–2000, when diamonds processed through General Electric's proprietary Pegasus Overseas Limited (GE POL) programme were found to be circulating in the trade without adequate disclosure. The incident constituted fraud under trade practice laws in most jurisdictions, prompted emergency responses from major gemmological laboratories, and ultimately produced lasting structural changes to how treated diamonds are identified, marked, and disclosed throughout the supply chain.

Background: What HPHT Treatment Does

High-pressure high-temperature treatment subjects a diamond to conditions approximating those of its original formation deep within the earth — pressures in the range of 50,000 to 70,000 atmospheres and temperatures exceeding 2,000 °C. When applied to certain Type IIa diamonds (those with negligible nitrogen impurities) and some Type Ib stones, this process can dramatically alter colour. Brown or near-colourless Type IIa diamonds, which owe their brownish hue to structural lattice defects accumulated over geological time, can be transformed into colourless, near-colourless, or even fancy-coloured stones — including rare and commercially valuable pinks and blues. The colour change is permanent and, critically, leaves no obvious visual trace detectable by standard gemological examination.

General Electric had been researching high-pressure diamond technology for decades, having famously synthesised the first laboratory-grown diamond in 1954. The colour-enhancement application, developed in partnership with Pegasus Overseas Limited, was patented and represented a commercially significant capability. The problem was not the technology itself but the manner in which treated stones entered commerce.

The 1999–2000 Disclosure Crisis

In late 1999, the Gemological Institute of America and other leading laboratories began encountering diamonds that displayed the optical and spectroscopic signatures of HPHT treatment — most notably, anomalous graining patterns, unusual fluorescence behaviour, and absorption features detectable under infrared and ultraviolet spectroscopy — yet were being submitted for grading without any declaration of treatment. The stones were, in many cases, accompanied by prior grading reports that made no mention of enhancement, because the treatment had been applied after original grading.

The GIA confirmed in early 2000 that a number of HPHT-treated diamonds had entered the market without disclosure, and that GE POL-processed stones could be identified by a faint laser inscription reading "GE POL" on the girdle — but that this inscription was not always present, and that some treated stones had been polished or re-cut in ways that removed it. The revelation sent a wave of alarm through the trade. Dealers who had unknowingly purchased treated stones faced significant financial exposure; consumers who had paid premium prices for apparently natural-colour diamonds had, in effect, been defrauded.

The Jewelers Vigilance Committee, the World Federation of Diamond Bourses, and national trade bodies in the United States and Europe issued urgent advisories. The Federal Trade Commission's existing guidelines on disclosure of gemstone treatments were invoked, making clear that failure to disclose a permanent colour treatment in a diamond constituted an unfair or deceptive trade practice. Similar provisions applied under consumer protection frameworks in the European Union and elsewhere.

Detection: The Gemmological Response

The crisis accelerated the development of detection protocols that might otherwise have evolved more gradually. The GIA, along with the International Gemological Institute (IGI), HRD Antwerp, and other laboratories, invested in spectroscopic instrumentation capable of identifying HPHT-treated stones with high reliability. Key diagnostic tools include:

• Infrared absorption spectroscopy (FTIR): HPHT treatment of Type IIa diamonds produces a characteristic absorption pattern in the infrared region that differs from untreated Type IIa stones and from Type Ia diamonds with normal nitrogen aggregates.
• Photoluminescence spectroscopy: Certain defect centres created or modified by HPHT treatment — including the H3 centre (at 503.2 nm) and the NV (nitrogen-vacancy) centre — produce diagnostic luminescence signatures under laser excitation.
• Ultraviolet fluorescence: HPHT-treated diamonds frequently display unusual fluorescence patterns, including strong, even blue fluorescence in Type IIa stones and, in some cases, phosphorescence.
• Strain birefringence patterns: Viewed under cross-polarised light, many HPHT-treated Type IIa diamonds display anomalous strain patterns distinct from those of untreated stones of the same type.

No single test is definitive in isolation; laboratories employ a battery of complementary techniques. The GIA formally updated its grading report language to flag stones requiring further testing, and introduced the notation "HPHT Annealed" or equivalent on reports for confirmed treated stones.

Mandatory Inscription and Regulatory Consequences

The most immediate structural remedy was the requirement — adopted by GE POL and subsequently reinforced by industry bodies — that all HPHT-treated diamonds bear a permanent laser inscription on the girdle identifying them as treated. GE POL's own inscription programme used the mark "GE POL"; later, as other entities began offering HPHT colour enhancement, the convention expanded to require inscriptions identifying the treatment generically (e.g., "HPHT Processed") or by the processing laboratory's designation.

The GIA and other major laboratories adopted policies of noting HPHT treatment prominently on grading reports and of declining to issue standard grading reports — as opposed to identification reports — for treated stones without disclosure notation. The Rapaport Diamond Report, the trade's principal price benchmark publication, addressed the valuation implications: HPHT-treated colourless diamonds trade at a significant discount to untreated stones of equivalent apparent colour and clarity, reflecting both the treatment itself and the residual market wariness generated by the non-disclosure episode.

In the United States, the FTC's Guides for the Jewelry, Precious Metals, and Pewter Industries (most recently updated in 2018) explicitly require disclosure of any treatment that affects a gemstone's value or durability. HPHT colour enhancement falls squarely within this requirement. Failure to disclose exposes sellers to FTC enforcement action, civil liability, and, in egregious cases, criminal fraud prosecution.

Market and Ethical Legacy

The HPHT non-disclosure episode is widely regarded as one of the most consequential trade ethics crises in the modern diamond industry. Its legacy operates on several levels.

First, it demonstrated that a permanent, visually undetectable treatment could enter a high-value commodity market at scale before the trade had developed either the detection infrastructure or the regulatory reflexes to intercept it. This sobering recognition has informed how the industry approaches subsequent treatment technologies — including laser drilling, fracture filling, and, more recently, the disclosure challenges posed by laboratory-grown diamonds.

Second, it established the principle that permanent marking of treated stones is not merely best practice but an ethical and, in many jurisdictions, legal obligation. The laser inscription convention that emerged from the GE POL controversy is now standard across a range of diamond treatments and has been extended, in modified form, to laboratory-grown diamonds.

Third, it elevated the role of independent gemmological laboratories as gatekeepers of treatment disclosure. The crisis gave the GIA and its peers both the mandate and the commercial incentive to invest heavily in treatment-detection science, producing a generation of spectroscopic and photoluminescence protocols that have substantially reduced — though not eliminated — the risk of treated stones passing undetected through the trade.

The episode also served as a cautionary case study in the relationship between proprietary technology and market transparency. GE and Pegasus Overseas Limited possessed a powerful and commercially valuable process; the failure was not in developing it but in allowing treated stones to reach consumers without the disclosure infrastructure that the trade's integrity required. That distinction — between innovation and transparency — remains central to ongoing debates about emerging treatments and laboratory-grown material.

Further Reading

• GIA Gems & Gemology: HPHT Annealing of Diamonds (Spring 2000)
• GIA Gems & Gemology: Gem News — HPHT-Treated Diamonds (Fall 1999)
• FTC Jewelry Guides — Disclosure Requirements