About Diamonds
The diamond is pure crystalline carbon — element 6, atomic number twelve, formed under extreme pressure at depths of 140 to 190 kilometres below the Earth's surface and carried to the upper crust by kimberlite and lamproite volcanic pipes erupting at velocities exceeding the speed of sound. It is the hardest natural substance known, the most thermally conductive material at room temperature, and, since the introduction of De Beers' marketing campaigns in the twentieth century, the world's most recognisable symbol of romantic commitment.
Diamond grading is built around the “4 Cs” framework formalised by GIA in the 1950s and now universally accepted across the trade: Carat (weight), Colour (graded D through Z on the colourless scale, with fancy colours graded separately), Clarity (graded on an eleven-tier scale from Flawless through I3), and Cut (proportions, polish, and symmetry, graded on a five-tier scale from Excellent through Poor). AGL Antwerp issues full 4Cs diamond certificates that match the analytical depth and presentational rigour of the major international laboratories: every report includes a calibrated colour-master comparison, a plotted clarity diagram drawn under 10X magnification, measured proportions taken on a Sarine non-contact system, and a documented fluorescence reaction under long-wave UV light.
Fancy-colour diamond grading is a separate discipline of considerable analytical complexity. Naturally coloured diamonds — yellow (cape series, canary), brown (champagne, cognac), pink (Argyle, Brazilian), blue (Cullinan-type, hydrogen-related), green (radiation-induced), orange, and the extraordinarily rare red — are graded on a nine-tier scale running from Faint through Fancy Vivid and Fancy Deep. The cause of colour is determined by FTIR and photoluminescence spectroscopy: nitrogen aggregation states distinguish natural Type Ia yellows from HPHT-treated Type Ib stones, boron substitution causes natural blue colour, and lattice damage from natural alpha-particle bombardment produces the rare green “Dresden Green” type.
Natural-versus-synthetic verification is now the single most important analytical task in commercial diamond grading. Laboratory-grown diamonds — produced by HPHT (high-pressure high-temperature) synthesis or CVD (chemical vapour deposition) — are chemically and structurally identical to natural diamond and indistinguishable to the eye even under high magnification. Detection requires DiamondView fluorescence imaging (HPHT synthetics show a distinctive cross-shaped or four-fold growth pattern; CVD synthetics show layered growth striations), photoluminescence spectroscopy (CVD synthetics show characteristic silicon-vacancy peaks at 736.5 nm), and FTIR analysis. AGL Antwerp's lab is equipped with the full DTC-derived screening and confirmation toolkit, and every diamond we examine is screened for synthetic origin as standard.
Treatment detection — HPHT colour treatment, irradiation, laser drilling, fracture filling, surface coating — is conducted on every fancy-colour stone we examine and on any colourless diamond where preliminary screening suggests treatment may have been applied. Every conclusion on the AGL diamond certificate is supported by recorded instrumental data; we do not issue grading reports on the basis of visual inspection alone, and we will not issue an “origin” report on a polished diamond unless that origin can be confirmed by trace-element analysis of cutting fragments or other forensic evidence.
How AGL certifies Diamonds
Every diamonds submitted to an AGL laboratory is examined by at least two senior gemologists and analysed using our standard instrumental package: refractive-index and specific-gravity measurement, microscopic examination under dark-field and fibre-optic illumination, UV-VIS-NIR absorption spectroscopy, FTIR spectroscopy for treatment detection, and LIBS or ED-XRF for trace-element analysis where origin is in question. Every conclusion on the certificate — species, variety, treatment, origin — is supported by recorded analytical data, and every certificate is recorded in our secure verification database for online authentication at any time.
For full service descriptions and turnaround times, see our Services page, or contact your nearest AGL laboratory for a written quotation.
