Lab Grown Diamond Creation: HPHT vs CVD
Lab-grown diamonds are real diamonds. They are chemically, physically, and visually the same as their natural counterparts.
The only difference lies in where they come from. Instead of forming over billions of years beneath the Earth’s surface, lab-grown diamonds are created in modern laboratories using advanced technology that replicates the conditions necessary for diamond formation.
In this guide, we’ll walk you through the two primary methods used to grow diamonds in a lab—High Pressure High Temperature (HPHT) and Chemical Vapor Deposition (CVD).
How Lab-Grown Diamonds Are Made
The creation of a lab-grown diamond begins with a diamond “seed”—a tiny sliver of natural or synthetic diamond. This seed is placed into a specialized lab environment where carbon atoms attach to its surface and crystallize, gradually forming a full-sized diamond.
Even though HPHT and CVD use this same basic principle, the environments they create differ a lot. Each method has unique benefits, and both can produce high-quality, gem-grade diamonds.
HPHT Method
High Pressure High Temperature (HPHT) was the first method developed to create diamonds. The method creates a setting that closely mimics the natural geological forces that form diamonds deep within the Earth.
In the HPHT process, a press applies extreme pressure of around 5 to 6 gigapascals to a carbon source, while exposing it to temperatures between 1,300°C and 1,600°C. Under these conditions, the carbon crystallizes around the diamond seed.
There are three main types of presses used: belt, cubic, and split-sphere (BARS). Each can grow diamonds in a matter of days to weeks.
HPHT is particularly effective at producing diamonds with high color grades; in fact, it’s also used in diamonds created by the CVD method to remove brown hues or enhance near-colorless grades.
While HPHT can yield diamonds with excellent clarity, metallic inclusions from the press environment are sometimes present.
CVD Method
Chemical Vapor Deposition (CVD) is a newer, more energy-efficient method that allows for greater control during the diamond growth process.
Like HPHT, it starts with a diamond seed, but instead of pressure, it relies on a gas mixture used inside a vacuum chamber. The mixture used is typically methane and hydrogen.
At temperatures between 800°C and 1,200°C, the carbon atoms in the gas break apart and begin to accumulate, layer by layer, onto the seed. This slow, controlled buildup creates a diamond with a flat, tabular crystal structure.
CVD is well-suited to making diamonds with high purity and fewer metallic inclusions. However, some CVD diamonds may show a brown or gray tint immediately after growth.
As discussed before, these can be treated using the HPHT method to improve their color and appearance—making it common for diamonds on the market to be grown through a combination of both processes.
What’s More Common Today?
While HPHT pioneered the field of lab-grown diamonds, CVD is now the more widely used method in commercial diamond production. Its scalability, efficiency, and precision make it the preferred technique for creating high-quality diamonds at larger volumes.
That said, HPHT remains essential—both as a primary growth method and as a post-treatment process to refine the color and structure of CVD-grown diamonds.
Conclusion
To the naked eye, there’s no way to tell whether a diamond was grown using HPHT or CVD. But gemological labs can distinguish between them using advanced testing tools that analyze inclusion patterns, growth structures, and trace elements.
No matter the process, lab-grown diamonds represent a remarkable blend of science and beauty, offering all the brilliance, hardness, and fire of natural diamonds at a more accessible price point.
If you’re considering a lab-grown diamond for your next piece, we warmly invite you to visit our studio in Dallas for a complimentary consultation.