Treatments and Enhancements

Treatments and enhancements aim to unnaturally improve the colour/clarity grade of a diamond.

Some of the most common techniques and methods to (unnaturally) enhance or improve the colour and clarity grades of diamonds are listed in the table below. Each method is then covered in more detail.


Aims to Improve

High-Pressure High-Temperature Treatment (HPHT)

Colour Grade

Colour Enhancement

Fracture Filling

Clarity Grade

Laser Drilling

High-Pressure High-Temperature Treatment (HPHT)

Treated DiamondsHigh-Pressure High-Temperature treatment (HPHT) was developed by General Electric to improve the colour of certain types of natural diamonds.

During the formation and subsequent transportation of diamond crystals from deep within the earth's crust to the surface, distortion of the crystal lattice causes some diamonds to have a brown body colour.

Only if the diamond has negligible nitrogen and boron can HPHT be successful. It is estimated that only 3 out of 10,000 diamonds have this combination and are thus suitable for treatment.

  • Only a very small percentage of natural-origin diamonds can be treated using HPHT — approximately 3 out of 10,000.
  • HPHT diamonds can be identified for further testing using DiamondSure™ technology.
  • Bellataire Diamonds are the most well-known brand of HPHT diamonds.
  • Full disclosure, including laser inscription on the girdle, is essential.
  • only sells Black HPHT Diamonds.

Colour Enhancement

Colour Treated Diamonds Diamonds that have been treated to produce fancy colours are called colour-treated or colour-enhanced diamonds.

The process to produce colour-enhanced diamonds involves artificially altering the colour of a diamond by exposing it to radiation and/or other methods. The colours produced are the full range of the spectrum.

  • Colour-treated diamonds are considerably less expensive than natural fancy coloured diamonds.
  • Colour-treated diamonds should definitely be disclosed to the consumer at the time of sale.
  • is only involved with natural fancy coloured diamonds — we do not sell colour-treated diamonds. We will supply treated black diamonds upon special request.

Fracture Filling 

Flash Effect Fracture filling is a post-cutting process that improves the clarity of a diamond, and is achieved through a process of filling surface-reaching cleavages, fractures and laser drill holes with glass or epoxy to make them less visible.

  • Fracture filling can be identified relatively easily under magnification by trained personnel. The main identifying characteristic is the "flash effect", which shows colour in the filled fracture.
  • Fillings can be damaged by high temperatures and acids, returning the diamond to its original clarity grade.
  • GIA's Gem Trade Laboratory — and other leading laboratories — will not grade fracture-filled diamonds.
  • Fracture filling should definitely be disclosed to the consumer at the time of sale.
  • will not have any association with fracture-filled diamonds.

Laser Drilling

Diamond Laser Drilling Laser drilling is another treatment that is designed to improve the clarity (and therefore appearance) of a diamond that contains dark inclusions.

A tiny hole is drilled into the diamond with a laser until it reaches the inclusion. The inclusion is then bleached or dissolved using acid. Some diamonds may have multiple drill holes.

  • Most laser drill holes are very difficult to find without the aid of magnification, especially if the inclusion is close to the surface.
  • Laser drill holes can be filled with glass or epoxy.
  • Laser drilling should be disclosed to the consumer at the time of sale.
  • will not purchase or sell laser-drilled diamonds.