How Are Lab-Grown Diamonds Made?

• Lab-grown diamonds are created from carbon through controlled technological processes.
• Both CVD and HPHT generally begin with a diamond seed.
• HPHT uses high pressure, high temperature and a metallic growth environment.
• CVD uses activated carbon-rich gases inside a controlled chamber.
• The rough crystal must still be cut and polished after growth.
• Post-growth treatment may be used to alter colour or improve appearance.
• CVD is not automatically better than HPHT, and HPHT is not automatically better than CVD.
• Growth method alone does not determine the quality of the finished diamond.
• Specialist laboratories can identify growth method and post-growth treatment.
• Environmental impact depends partly on the energy source and efficiency of the facility.

Both major growth methods normally begin with a diamond substrate, commonly called a diamond seed.

The seed acts as the structural foundation for new diamond growth. It gives carbon atoms an existing diamond crystal pattern upon which they can form.

A diamond seed is not comparable to planting a biological seed. It does not contain a living organism, and it does not grow through a natural reproductive process. It is a precisely prepared piece of diamond material placed inside specialised equipment.

The seed must be selected and prepared carefully. Surface quality, orientation and cleanliness can affect how the new crystal develops. GIA explains that both CVD and HPHT use a diamond substrate to provide the crystal blueprint from which the new laboratory-grown diamond develops.

HPHT stands for High Pressure High Temperature. This method creates an environment of intense heat and pressure. It was the first commercially successful method used to produce diamonds and remains an important production process.

The carbon source is positioned within a specialised growth cell. Under high temperature and pressure, the metallic material melts and helps dissolve the carbon. Carbon moves through the molten metal environment and crystallises around the seed. Over time, the seed develops into a larger rough diamond crystal.

What does an HPHT rough crystal look like? The rough crystal does not initially resemble a finished jewellery diamond. Its external shape reflects the conditions under which it grew. It may have distinct cuboctahedral crystal faces and growth sectors that become useful during professional identification.

Can HPHT introduce inclusions? Yes. Because metallic materials are involved in the growth environment, some HPHT diamonds can contain microscopic metallic inclusions. Their presence, size and visibility vary and are documented during grading.

High Pressure High Temperature (HPHT) reproduces the extreme heat and pressure of the earth to grow crystals.

CVD stands for Chemical Vapour Deposition. Unlike HPHT, CVD does not depend on creating the same extreme pressure environment. It uses a controlled vacuum chamber containing carbon-rich gas.

A thin diamond seed or substrate is placed inside the chamber. The chamber is then sealed, and gases—commonly involving hydrogen and a carbon source such as methane—are introduced. Energy (often microwave radiation) is applied to activate the gases, creating a plasma in which carbon-containing molecules break apart. Carbon atoms then settle onto the diamond seed, growing layer by layer into a diamond crystal.

Does CVD create a diamond instantly? No. Crystal growth requires controlled conditions and careful monitoring. The manufacturer must manage factors such as gas composition, pressure, temperature, energy input, and chamber cleanliness. Growing too quickly can compromise crystal quality.

Why is CVD described as layer-by-layer growth? CVD growth occurs as carbon is deposited onto the prepared diamond substrate. This creates a layered growth structure. While these patterns are invisible to the eye, advanced spectroscopic instruments can detect them to confirm the CVD method.

Chemical Vapour Deposition (CVD) grows diamonds layer by layer from carbon-rich plasma gas.

There is no single universal production time. Growth time varies according to the growth technology, desired crystal size, growth rate, and equipment efficiency.

GIA research indicates that HPHT growth can range from hours to weeks, depending on size and quality. A larger crystal does not merely require a longer uninterrupted run; manufacturers must manage growth stability throughout the cycle to prevent cracks or major impurities.

Removing the crystal from the reactor or press does not produce a finished jewellery diamond. The rough crystal passes through three additional skilled stages:

1. Rough Diamond Assessment: The newly grown crystal is scanned and planned. Cutting software models different options to determine expected finished shapes and facet layout, balancing cut quality, clarity, shape, and carat weight.

2. Cutting the Diamond: The rough crystal is cut using laser technology or traditional diamond saws. It is then shaped and faceted. Popular shapes include Round, Oval, Pear, Emerald, Cushion, Radiant, Princess, Marquise, and Heart.

3. Polishing and Finishing: Each facet is carefully polished. Polishing affects the smoothness and light reflection of the surface. Poor polishing creates micro-lines that interfere with the diamond's trademark brilliance.

Laser technology and skilled craftsmanship transform the rough diamond crystal into a faceted gemstone.

Can they receive post-growth treatment? Yes. Some laboratory-grown diamonds receive treatments (like high-pressure annealing) to modify colour or improve transparency. Any treatment is material information that must be disclosed on grading reports.

Are they automatically sustainable? Not automatically. While lab-grown diamond production avoids mining, the reactors and presses require electricity. The environmental footprint depends heavily on the energy source (e.g. solar/wind vs coal) and the efficiency of the grower's facility.

Are they made from natural diamonds? The process begins with a small diamond seed. While the seed provides the crystal blueprint, the finished crystal consists almost entirely of carbon atoms newly crystallised around it.

Aurelia Royale's collection includes jewellery featuring laboratory-grown diamonds across earrings, bracelets, necklaces, pendants, rings and coordinated designs. When considering a piece, review the product's design details and verifiable certifications. Explore the Aurelia Royale jewellery collection or contact our team for assistance.