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Fundamental Research
Fundamental Research

Antwerp diamond research
The activities of the research department are crucial in supporting HRD Antwerp’s main activity, i.e. the issuing of diamond certificates by Diamond Lab. The determination of the 4 Cs requires state-of the-art equipment and techniques which are in general not commercially available. HRD Antwerp Research defines the necessary developments to secure and enhance the 5th C (Confidence) on the diamond certificate and collaborates closely with diamond research institutes and centers, in particular with WTOCD.

The general aims of HRD Antwerp Research are:

    • To develop non-destructive methods for the identification of treated and synthetic diamonds
    • To implement the methods of identification and detection in the process of HRD Antwerp Diamond Lab
    • To inform the diamond community on scientific and technological developments related to gem diamond
    • To provide a Scientific Advice Service to support the diamond community
Research topics

Synthetic diamond

At present, two methods exist to produce large synthetic diamonds of gem quality: High Pressure High Temperature (HPHT) and Chemical Vapour Deposition (CVD).
In the HPHT process, natural diamond growth parameters are imitated. The HPHT method dates from the 1950s. Large gem quality stones are known since the 1970s.

Synthetic diamond  
Schematic setup of a “Belt” apparatus for the production of HPHT synthetic diamonds 

Synthetic diamond  
Rough HPHT synthetic diamond 

CVD diamond is created from the gas phase, by deposition of carbon from a plasma; the CVD method for producing synthetic diamond has existed for more than half a century, but gem quality stones are still very rare commercially.

CVD diamond Synthetic diamond
Schematic setup of a system for the production of
CVD synthetic diamond.
Polished CVD synthetic diamond 


The purpose of a treatment is to enhance one or more of the four Cs of a diamond, increasing the value of the stone. Especially clarity and colour treatments are important and they are known since a long time. In fact diamonds have been treated long before man was capable of making synthetic diamonds. Both natural and synthetic diamonds can be treated.
Colour treatments
Treatment Result How? Example
Irradiation Create blue to green (fancy) colours High energy irradiation (e.g. 1 MeV electrons) Irradiation exampleIrradiation
Blue-green irradiated diamond
Irradiation + heating Create yellow, orange, pink and even red fancy colours High energy irradiation + heating up to 1000°C Irradiation + heating exampleIrradiation + heating
Yellow diamond, type Ia, irradiated and heat treated
Coating Create all fancy colours
Blue coating makes a yellowish stone more colourless
Easily damaged
Surface layer of coloured foreign material
Synthetic CVD diamond layer is possible
Coating exampleCoating example
Damaged coating on a polished diamond
HPHT (High Pressure High Temperature) treatment Make a stone more colourless (type IIa or IaB), or create fancy colours High temperature (>2000°C)
High pressure (>70000 atm)
HPHT exampleHPHT example
Blue diamond, type IIb, HPHT treated
HPHT + irradiation + heating Create pink to red colours HPHT + High energy irrradiation + heating up to 1000°C (HPHT + irradiation + heating) example(HPHT + irradiation + heating) example
Pink diamond, type Ia, HPHT treated, irradiated
and heated
High temperature treatment Create black colour Heating to around 1000°C (oxygen free atmosphere)
Boart quality diamond
HT exampleHT example
Black diamond, heat treated

Clarity treatments
Treatment Result How? Example
Laser drilling + deep boiling Improved clarity because of reduced visibility of inclusion(s) Laser hole drilled from inclusion to surface + inclusion bleached chemically Laser drilling exampleLaser drilling
Laser drilling in a polished diamond
Fracture filling Improved clarity because of reduced visibility of fractures High refractive index glass introduced in the fractures Fracture filling exampleFracture filling
“Flash effect” colours in a fracture filled diamond

Scientific Advice

HRD Research offers a scientific advice service to the diamond sector. Supported by a wide range of analysis instruments, practical solutions are offered to challenges of a scientific nature. These challenges can relate to the necessity of identifying synthetic and treated diamonds, the evaluation of rough stones, the identification of different types of diamonds, etc. The aim is to provide support to diamond the sector, and to enhance consumer confidence.

Contact information

HRD Antwerp – Research
Hoveniersstraat 22
B-2018 Antwerpen
Tel: +32 3 222 06 11
Fax: +32 3 222 06 99

Website: www.hrdantwerp.be