Lab Grown Diamonds
Lab-grown diamonds are diamonds that are created in a laboratory using advanced technology. Lab diamonds are chemically, physically, and optically identical to mined diamonds and have historically been referred to as "cultured" or "synthetic" diamonds.
In 2018, the Federal Trade Commission (FTC) declared that lab grown diamonds are equal to mined diamonds and should be described to consumers in the same way. This guidance was intended to ensure consumers are informed when making their diamond purchasing decisions.
How are Lab Diamonds Formed?
- High pressure-high temperature (HPHT)
- Chemical vapor deposition (CVD).
HPHT (High Pressure, High Temperature)
HPHT recreates the conditions under which diamonds form in the earth's mantle.
A diamond seed is placed in a growth chamber alongside a solid carbon source — graphite — and a metal catalyst, typically a blend of iron, nickel, and cobalt. The chamber is brought to roughly 1,300–1,600°C at pressures around 5–6 GPa. Under these conditions the carbon dissolves into the molten metal and crystallises onto the seed.
The crystal grows outward in fourteen directions at once, forming a cuboctahedron. Growth takes several days to several weeks depending on the size of the stone, and the process can be controlled to produce colourless or coloured diamonds.
HPHT is the older of the two methods, and the technology has matured considerably. Historically, HPHT stones tended toward a yellow tint caused by nitrogen. Manufacturers have since largely engineered that out.
A diamond seed is placed in a growth chamber alongside a solid carbon source — graphite — and a metal catalyst, typically a blend of iron, nickel, and cobalt. The chamber is brought to roughly 1,300–1,600°C at pressures around 5–6 GPa. Under these conditions the carbon dissolves into the molten metal and crystallises onto the seed.
The crystal grows outward in fourteen directions at once, forming a cuboctahedron. Growth takes several days to several weeks depending on the size of the stone, and the process can be controlled to produce colourless or coloured diamonds.
HPHT is the older of the two methods, and the technology has matured considerably. Historically, HPHT stones tended toward a yellow tint caused by nitrogen. Manufacturers have since largely engineered that out.
CVD (Chemical Vapor Deposition)
The CVD process starts with a small diamond seed, usually a natural diamond, which is then placed in a vacuum chamber. A mixture of gases, such as methane and hydrogen, are then ionized by using high-energy sources like microwaves or plasma to break down the gasses which release carbon atoms. The carbon atoms then settle onto the diamond seed, layer by layer, forming a new diamond. The process is carefully controlled to ensure that the carbon atoms settle onto the diamond seed in a way that produces a high-quality diamond. The process typically takes several weeks to create a single diamond, depending on the desired size of the diamond and the process can be controlled to produce colourless or coloured diamonds.
What are the main difference between CVD & HPHT lab created diamonds?
The main difference between CVD and HPHT lab created diamonds is the method used to grown them. CVD (chemical vapor deposition) diamonds are created using plasma containing hydrogen and methane. The gases are heated and broken down into ions of hydrogen and carbon which are then deposited onto the diamond’s surface at the atomic level. HPHT (high-pressure, high-temperature) diamonds are created from a natural diamond seed that is heated and pressurized to mimic the conditions in which naturally occurring diamonds are formed.
Both methods produce real diamonds, and both can produce beautiful stones, but they are not interchangeable, and the differences have grown clearer as the industry has matured.
HPHT grows a cuboctahedral crystal in fourteen directions from a solid carbon source. CVD grows a tabular crystal in one direction from gas. That structural difference drives everything downstream: the two methods carry different inclusion types, different native colour characteristics, and different economics at different stone sizes. HPHT is the more productive method at smaller sizes; CVD scales better to large centre stones, which is why most large lab-grown diamonds on the market today are CVD-grown.
The most consequential difference is not a property of the finished stone at all. It is a question of how the stone was made, and whether it needed correcting afterward.
HPHT grows a cuboctahedral crystal in fourteen directions from a solid carbon source. CVD grows a tabular crystal in one direction from gas. That structural difference drives everything downstream: the two methods carry different inclusion types, different native colour characteristics, and different economics at different stone sizes. HPHT is the more productive method at smaller sizes; CVD scales better to large centre stones, which is why most large lab-grown diamonds on the market today are CVD-grown.
The most consequential difference is not a property of the finished stone at all. It is a question of how the stone was made, and whether it needed correcting afterward.