Diamonds, nature's hardest substance, have long been prized for their brilliance and rarity. However, with the advancement of technology, it is now possible to grow diamonds in laboratories that have the exact same physical and chemical properties as natural diamonds. Lab-grown diamonds are not only more affordable, but the production process is also more environmentally friendly and controlled. So how are these ‘miracles of science’ made?

## Two main manufacturing methods

There are two main established technological routes for laboratory-grown diamonds: High Pressure High Temperature (HPHT) and Chemical Vapour Deposition (CVD), each of which has its own characteristics and is suitable for the production of diamonds for different needs and purposes.

### 1. High Pressure High Temperature Method (HPHT)

The High Pressure High Temperature (HPHT) method simulates the natural conditions under which natural diamonds are formed deep within the earth's crust. The history of this method dates back to the 1950s, when researchers at General Electric first successfully synthesised diamonds in the laboratory.

The HPHT method involves placing a high-purity carbon source (usually graphite) with a metal catalyst (such as iron, nickel or cobalt) in a high-pressure resistant device. A pressure of about 5-6 GPa (equivalent to 50-60,000 times atmospheric pressure) and a high temperature of 1300-1600°C are then applied. Under these extreme conditions, the carbon atoms rearrange themselves to form the crystal structure of the diamond.

The advantage of the HPHT method is that it can produce gem-quality diamonds relatively quickly (usually a few days to a few weeks), and is particularly suitable for the production of coloured diamonds such as yellow or blue. However, this method is extremely demanding and the diamonds produced tend to be small in size and may contain metal inclusions.

### 2. Chemical vapour deposition (CVD)

Chemical vapour deposition (CVD) is a relatively new technology that only began to be used in diamond production in the 1980s. Instead of mimicking natural conditions, this method uses a chemical reaction to form diamonds by depositing carbon atoms in a low-pressure environment.

The CVD process involves placing a thin slice of diamond seed crystal (usually produced by the HPHT method) into a vacuum chamber and passing it through a carbon-containing gas (usually methane) and hydrogen. The gases are then ionised into a plasma by microwaves or other means, and the carbon atoms are separated from the gases and deposited in layers on the seed crystal, gradually forming a diamond crystal.

The CVD method has the advantage of being able to produce larger sized diamonds of higher purity (growth rates of approximately 0.1-10 microns per hour) and is particularly suited to the production of colourless or near colourless diamonds. However, the growth cycle is long and it may take several weeks before a usable diamond is available.

## From rough crystals to sparkling gems

Whether produced by HPHT or CVD, diamonds start out as rough crystals that need to undergo the same cutting and polishing processes as natural diamonds to become sparkling gems.

First, experts study the internal structure and optical properties of the raw stone to determine the best cut to maximise its brilliance and value. It is then cut using a diamond powder-coated saw blade or laser. This is followed by a number of processes, including grinding and polishing, to give the diamond its familiar appearance.

## The future of laboratory diamond applications

The applications of laboratory-grown diamonds go far beyond the field of jewellery. Due to their excellent physical properties (high thermal conductivity, high hardness, chemical inertness, etc.), they have a wide range of applications in industry:

- Cutting tools: diamond cutting tools and abrasives

- Thermal management: heat sinks for electronic devices

- Optical windows: high-power laser systems

- Quantum computing: as carriers of quantum bits

- Medical applications: surgical tools and implant coatings

As technology advances, the cost of producing laboratory diamonds continues to fall and their quality continues to improve. Today, even professional gemologists need specialised equipment to distinguish high-quality laboratory diamonds from natural diamonds. This not only provides consumers with more choices, but also opens up great prospects for industrial applications of diamonds.

Laboratory-grown diamonds represent an important achievement in materials science and engineering, blurring the line between ‘natural’ and ‘man-made’ and demonstrating man's ability to replicate and even improve upon the wonders of nature. As the concept of sustainable development becomes more widespread, it is likely that this environmentally friendly, traceable method of diamond production will occupy a more important market position in the future.

If you're considering buying diamonds, lab-grown diamonds are a cost-effective, sustainable option!