CVD Diamond Meaning
There are two common methods for creating lab-grown diamonds: High Pressure High Temperature (HPHT) and Chemical Vapor Deposition (CVD). CVD diamonds are lab diamonds formed through the Chemical Vapor Deposition process, which uses carbon gas to grow diamonds in a controlled environment.
In CVD, a seed diamond is placed inside a vacuum chamber filled with heated hydrogen and methane-rich gas. When the chamber reaches a certain temperature, the gas molecules break down, and layers of crystallized carbon form around the seed, creating a larger diamond.
CVD vs. HPHT Diamonds
CVD and HPHT diamonds are the two main methods for growing lab diamonds. The primary differences between CVD and HPHT diamonds lie in their production techniques and conditions:
Process
CVD diamonds are grown through a chemical reaction in a vacuum chamber, while HPHT diamonds form under simulated high-pressure, high-temperature conditions like those found within the Earth.
Growth Conditions
CVD diamonds are developed in a lower-pressure environment with controlled carbon gas exposure, while HPHT diamonds are grown under extreme pressure (5-6 GPa).
HPHT Treatment
Some CVD lab-grown diamonds are subjected to HPHT conditions to improve their color, typically turning brownish diamonds into colorless or near-colorless ones.
How CVD Diamonds Are Made
CVD diamond growth relies on Chemical Vapor Deposition, which involves breaking down carbon gases to form diamond crystals. Here’s an overview of how the process works:
- Seed Placement: A disc containing 15-30 small diamond seeds (tiny pieces of natural or lab diamond) is placed in the growth chamber.
- Gas Activation: Inside the chamber, a plasma ball of superheated methane and hydrogen gases is generated.
- Heat Increase: The chamber temperature is raised to 700-1200°C.
- Diamond Formation: Activated methane and hydrogen gases adhere to the seeds, repeatedly forming carbon layers over days or weeks, replicating the crystal structure of the original diamond seed and forming a pure diamond crystal.
- Monitoring and Cutting: Technicians monitor the diamond growth and remove the crystals once they are the desired size and ready for cutting. The lab diamond is then polished and shaped, preparing them for jewelry settings.
This precise process enables manufacturers to control factors like growth rate, clarity, and color for optimal quality.
How to Identify CVD Diamonds
The differences between natural diamonds, HPHT-grown diamonds, and CVD-grown diamonds are undetectable to the naked eye. At Brilliant Earth, we offer lab reports on all our diamonds for more information on a diamond’s origin and characteristics.
