What Are Treated Diamonds? From Technology, Differences to Identification

In the diamond consumer market, one question is being asked by more and more buyers: 'Is the colour of this diamond natural, or has it been treated?'

So what exactly is a treated diamond? How is it 'treated'? And how can consumers identify and judge it?

1. What Is a Treated Diamond? Core Definition

A treated diamond refers to a natural or lab‑grown diamond whose colour has been altered through artificial processing methods. These methods include irradiation, high pressure high temperature (HPHT), coating, and others, with the aim of improving the diamond's appearance or enhancing its commercial value.

However, there is an important difference between treated and untreated diamonds: the origin of the colour. Untreated diamonds obtain their colour naturally during their formation or growth process; treated diamonds have their colour 'manufactured' through later artificial intervention.

2. Technical Principles of Treated Diamonds: How Is Diamond Colour Artificially Improved?

At a fundamental level, the colour of a diamond depends on defects and impurities in its internal crystal lattice structure. Different types of defects absorb different wavelengths of light, thus displaying different colours.

The mainstream colour‑treatment technologies currently include:

（1）. High Pressure High Temperature (HPHT) Treatment

HPHT treatment is one of the most widely used techniques, especially in the CVD lab‑grown diamond sector.

Technical principle: HPHT treatment simulates the high‑temperature, high‑pressure environment deep within the earth, causing impurity atoms and defects to migrate and recombine, thereby eliminating or reducing defects that cause undesirable colours.

（2）. Irradiation Treatment (combined with annealing heat treatment)

Irradiation treatment is another important colour‑enhancement technique, particularly widely applied to coloured diamonds.

Principle: Irradiation treatment uses high‑energy rays (such as electron beams or neutrons) to irradiate the diamond, changing its colour. The basic mechanism is that radiation particles collide with carbon atoms in the diamond, knocking atoms out of their lattice positions and creating colour centres. Different colour centres correspond to different light‑absorption characteristics, thus giving the diamond specific colours.

3. Treated vs Untreated Diamonds: Core Differences at a Glance

The core differences between the two categories are mainly reflected in the following dimensions:

Colour origin
Treated diamonds acquire their colour through later artificial processing, mainly HPHT annealing, irradiation, etc. Untreated diamonds (i.e., as‑grown diamonds) obtain their target colour directly in the reactor through precise control of growth parameters. This is the most fundamental difference.

Physical and chemical properties
There is no difference in physical properties or chemical composition between the two. Treatment changes only the colour appearance, not the material essence. A treated diamond is not a 'fake diamond' nor an 'inferior diamond'.

Price difference
Under the same 4C parameters (colour, clarity, cut, carat weight), treated diamonds are typically priced at only one‑third to one‑half that of untreated diamonds. This price gap arises from differences in manufacturing costs – treatment is a technological path that achieves a high‑quality appearance at a lower cost.

Colour stability
The stability of treated colours depends on the specific technique used. HPHT and irradiation treatments alter the diamond structure at the atomic level and are permanent changes – they do not fade over time. Coating treatments only affect the surface and are less stable. Untreated diamonds, by contrast, have naturally stable colours with no risk of fading.

4. How Can Consumers Identify Treated Diamonds? The Only Reliable Method

An important reminder: treated diamonds cannot be identified by the naked eye or a magnifying loupe.

The only authoritative and accurate identification method is to check the official laboratory certificate.

Taking the industry‑standard IGI (International Gemological Institute) certificate as an example:

• The certificate clearly states whether the diamond has undergone post‑growth treatment.

• If the diamond is in its original, untreated state, the certificate will specifically note:'As grown with no indication of post‑growth treatment.'

By relying on authoritative certificate notations, you can 100% distinguish treated diamonds from untreated diamonds and completely avoid consumer pitfalls.

5. Summary: View Treated Diamonds Rationally, Buy According to Your Needs Without Pitfalls

Treated diamonds are a product of technological progress in the jewellery industry. They are not counterfeit or adulterated – they simply use modern processes to optimise a diamond's natural imperfections.

Core principles when buying a diamond: Do not reject treated diamonds outright, and do not blindly pursue untreated diamonds. Read the certificate carefully, understand the product attributes clearly, and choose according to your own budget – that is the best purchasing approach.

If you have any questions during your diamond or jewellery selection – about certificate interpretation, the difference between treated and untreated, or how to make the best choice based on your budget – feel free to consult our professional team at any time.