GE POL is the trade designation for the first commercially deployed high-pressure, high-temperature (HPHT) treatment programme applied to near-colourless gem diamonds, launched in 1999 through a collaboration between General Electric and Pegasus Overseas Limited, the latter a subsidiary of Lazare Kaplan International. Diamonds processed under this programme were subsequently marketed under the brand name Bellataire. The treatment targets brown-tinted diamonds of type IIa — and, in certain cases, type Ia — chemistry, converting them to stones grading D through H on the GIA colour scale. Its commercial introduction marked a watershed moment in diamond gemmology: for the first time, a permanent colour alteration of gem-quality diamonds was available at industrial scale, compelling laboratories, dealers, and regulators to develop new disclosure standards and detection protocols.

Scientific Basis

The brown colouration found in many natural diamonds — particularly those of type IIa, which are characterised by an absence or near-absence of nitrogen impurities — is generally attributed to plastic deformation of the crystal lattice during the stone's geological history. This deformation introduces structural defects, notably vacancy clusters and dislocations, that absorb light preferentially in the visible spectrum and produce a brownish body colour. HPHT processing subjects the diamond to conditions approximating those of its original formation: pressures in the range of 5–7 gigapascals and temperatures exceeding 1,800 °C. Under these extreme conditions, the lattice defects responsible for brown colouration are partially or fully annealed, restoring a colourless or near-colourless appearance.

Type IIa diamonds are the primary candidates for GE POL treatment because their colour is almost exclusively structural in origin. Certain type Ia diamonds — those in which nitrogen is present in aggregated form — may also respond to HPHT processing, though the results are less predictable and the treatment can in some instances produce yellow or fancy colours rather than colourlessness.

Commercial History and the Bellataire Brand

General Electric had long possessed expertise in synthesising diamonds under high pressure, having produced the first laboratory-grown diamonds in 1954. By the late 1990s, GE researchers had established that the same class of equipment could be used to alter the colour of natural gem diamonds. The partnership with Pegasus Overseas Limited — which provided access to rough diamond supplies and the cutting and polishing infrastructure of Lazare Kaplan — allowed the technology to be translated into a commercial product.

The Bellataire brand was positioned as a premium offering: treated stones were presented as natural diamonds whose colour had been optimised rather than disguised, and the programme emphasised full disclosure as a selling point. Retail prices for Bellataire diamonds were set below those of untreated stones of equivalent colour grade, reflecting the treatment premium that the market applies to natural, unenhanced colour.

The programme attracted immediate and intense scrutiny from the diamond trade. The Diamond Trading Company (then the marketing arm of De Beers) and major industry bodies expressed concern about undisclosed treated stones entering the supply chain. These concerns accelerated the development of laboratory detection methods and prompted the adoption of mandatory girdle inscription as a disclosure mechanism.

Girdle Inscription and Disclosure Requirements

All diamonds processed through the GE POL programme are laser-inscribed on the girdle with the text GE POL or, for stones marketed under the retail brand, Bellataire. This inscription serves as a permanent, visible record of treatment and is a condition of the programme's commercial operation. The requirement for disclosure is consistent with the standards of the World Jewellery Confederation (CIBJO), the Jewelers of America, and the GIA, all of which mandate that HPHT treatment be disclosed at every point of sale.

The girdle inscription, while permanent under normal conditions, is not indestructible: re-polishing of the girdle could remove it. Gemmological laboratories therefore do not rely on inscription alone when issuing reports on suspected HPHT-treated diamonds.

Laboratory Detection

The GIA and other major laboratories — including the International Gemological Institute (IGI) and the Gemmological Institute of Great Britain (Gem-A's laboratory) — have developed reliable protocols for identifying HPHT-treated diamonds. Detection rests on several converging lines of evidence:

• Infrared spectroscopy: Type IIa diamonds are identified by the absence of the nitrogen-related absorption features present in most natural diamonds. A type IIa stone with a D-to-H colour grade warrants immediate scrutiny, as such combinations are rare in nature.
• Photoluminescence spectroscopy: HPHT treatment produces characteristic luminescence features, including emissions associated with nickel-related defects and the 637 nm nitrogen-vacancy centre, that differ from those seen in untreated type IIa diamonds.
• UV fluorescence: HPHT-treated diamonds frequently display unusual fluorescence patterns under both long-wave and short-wave ultraviolet illumination, including strong, sometimes streaky fluorescence and phosphorescence not commonly observed in untreated stones.
• Strain patterns: Examination under cross-polarised light may reveal anomalous extinction patterns consistent with the residual lattice strain that persists after treatment.

GIA grading reports for diamonds identified as HPHT-treated include a notation to that effect, and the laboratory will not issue a standard grading report for a treated stone without this disclosure. The combination of girdle inscription and laboratory identification means that GE POL diamonds are among the more transparently disclosed treated gemstones in the trade.

Effect on Diamond Properties

HPHT treatment as applied in the GE POL programme is permanent under all conditions encountered in normal jewellery wear. The process does not affect the clarity grade of the diamond, nor does it alter hardness, specific gravity, or refractive index — all of which remain those of natural diamond. The treatment changes only the distribution and character of lattice defects, with the consequence that colour is altered. There is no known mechanism by which the treatment could reverse under ambient conditions.

It is worth noting that HPHT treatment can, in some diamonds, improve clarity by dissolving certain types of inclusions, though this is not the primary objective of the GE POL programme and is not consistently achieved.

Market Position and Trade Significance

The introduction of GE POL treatment fundamentally altered the market for type IIa diamonds. Before 1999, large, brown type IIa rough — sometimes called "Cape" or "off-colour" material — traded at a significant discount to colourless equivalents. The possibility of HPHT upgrading introduced uncertainty into valuations of high-colour type IIa stones, since buyers could no longer assume that an apparently colourless type IIa diamond had achieved its colour entirely through natural processes.

This uncertainty has had lasting effects on how laboratories and sophisticated buyers approach type IIa diamonds. A type IIa diamond submitted for grading is now routinely subjected to additional spectroscopic testing precisely because the population of natural colourless type IIa stones overlaps with the population of HPHT-treated stones in terms of visible appearance. The GIA notes on its reports whether a diamond is type IIa, and this designation itself signals the need for careful treatment screening.

In the years following the GE POL launch, other operators entered the HPHT treatment market, and the technology has since been applied not only to near-colourless enhancement but also to the production of fancy-coloured diamonds — particularly blues and pinks — from suitable starting material. The GE POL programme thus served as the commercial proof of concept for a broader category of HPHT colour modification that continues to evolve.

Further Reading

• GIA Gems & Gemology: "HPHT Annealing of Diamonds" — Shigley et al., Spring 1999
• GIA Gems & Gemology: "Identification of HPHT-Treated Diamonds" — Fall 2000
• GIA: Diamond Treatments Overview