After the successful effort to synthesise diamonds, for the past 50 years, tons of diamonds were reproduced mainly for industrial applications such as diamond saw blades and drill bits for oil and gas drilling. Back then, the only method to create diamonds was the High Pressure High Temperature (HPHT) method. As the name suggests, it implies extreme heat and pressure that simulates the natural conditions where diamonds are formed, up to 200 kilometres below the earth. This method, however, requires lots of energy to operate and was unable to produce diamonds with decent size and clarity, therefore was futile to compete against the economy of conventional diamond mining. Today, the advancement of technology significantly improved the creation of lab-grown diamonds with greater efficiency, using a method called Chemical Vapour Deposition (CVD).

With CVD’s greater competency, lab-grown diamonds have gradually gained friction in the market after successfully manufacturing high quality lab-growns that even trained gemmologists would not be able to distinguish without advanced instruments. Well equipped with noteworthy affordability and the highly favourable “ethical sourcing”, the price of lab-growns now can be 10 or more times less compared to a natural diamond. In the end, who does not like a low-cost diamond that shows no physical and optical differences to a natural diamond.

TYPES OF DIAMONDS

Chemically, diamonds are pure crystallised carbon. In most natural diamonds, it contains colour-causing elements such as nitrogen and boron turn diamonds yellow and blue respectively, though nitrogen being the most common trace element in them. Pink and red diamonds, however, are not caused by impurities but structural deformation which can be seen within the diamond through a microscope in the form of parallel bands known as “graining” or lamellae.

Whether impurities present or not, diamonds are divided into two categories to describe its chemical composition and atomic structure: Type l and Type ll. These two categories then further subcategorised into Type la and Type lb, and Type lla and Type llb.

Type l - contains sufficient nitrogen atoms measurable through advanced instruments.

Type la (laA & laB)

Nitrogen atoms occur in aggregate formation.
Type laA - nitrogen atoms in close proximity, usually adjacent to one another.
Type laB - four nitrogen atoms symmetrically surround a vacancy that is typically occupied by a carbon atom.
Makes up almost 95% of natural diamonds.
Colourless, yellow, brown, pink, and violet, all can occur in type la.

Type lb

Nitrogen atoms occur in isolation from one another.
A rare type of diamond that shows excellent yellow colouration, often being termed as “canary” in the trade.
Brown and orange diamonds often are type lb.

While colours of natural diamonds come from impurities or structural abnormalities, only HPHT products are able to be mixed with impurities during the growing process. As such: high amounts of boron creates blue diamonds; nickel sometimes creates green diamonds; and nitrogen creates intense yellow diamonds. CVD synthesis process on the other hand, is unable to do so and post-growth treatments often are required in order to get attractive fancy colours. Post-growth treatments involve HPHT, irradiation, annealing, or all of the above to obtain different colours.

Putting products under high pressure and high temperature to alter the diamond's colour.
Works on all types of diamond, except type la if were to make it colourless
Type lb gives out yellow colour, type lla becomes colourless or pink, and type llb turns blue.

This process involves exposing materials to radiation.
Works for all types of diamond.
Able to produce green to blue diamonds

A form of heat treatment involving heating in a controlled temperature and cooling process, with lower temperature and pressure.
Often used after the irradiation process.
More commonly done to lower quality natural black diamonds as a standalone treatment.

Generally type l diamonds exhibit intense yellow, orange, pink, and red.
Rarely done on type ll diamond due to lack of impurities and resulting in pale colours.

This combo can be applied on type la & lla diamonds.
Causes the material to have intense pink, red, or orange colouration.

FEATURES OF NATURAL DIAMONDS VS LAB-GROWN DIAMONDS

In contrast to the almost undetectable traces of the above treatments, gemstones occasionally host eye visible inclusions observable with or without magnification. Inclusions can be in the form of solid crystals, liquid, gas, or fractures and fissures. These are important sources of data which shed light on the conditions in which they are formed and chemicals that they are exposed to.

Natural crystal inclusions are the most conclusive in determining whether a gemstone is naturally formed or lab grown. Such inclusions are foreign minerals that can, but not always, retain their original shape and habit which can be extremely helpful since lab-grown gemstones would not have such inclusions. These natural inclusions can form before, during, or after the formation of the host gem.

HPHT productions occasionally have recognisable inclusions that can be identified by using a microscope or ultraviolet light (UV), inclusions such as metallic flux and cross-like growth or colour zoning. During the HPHT process, a carbon-based starting material would be placed in a crucible filled with molten metal flux consisting of iron, nickel, or cobalt. The purpose of the flux is to lower the temperature and pressure for the diamond’s growth. The molten flux may be enclosed within the synthesised diamond. HPHT flux inclusions looks like a highly metallic and opaque liquid, and if a diamond is highly included with these, it is able to be attracted by magnet.