What is The Difference Between Lab Diamond HPHT And CVD Diamonds
Everyone’s not only talking about lab grown diamonds, but most conscious consumers are opting to buy lab diamonds as opposed to mined diamonds.
Lab cultured diamonds are made through two techniques — High Pressure High Temperature (HPHT) and Chemical Vapor Deposition (CVD). In this blog, we’ll focus on learning more about these two methods and how you can identify one diamond from the other.
Let’s get started!
Methods to Manufacture Lab Grown Diamonds
Laboratory diamonds are made with two methods. Let’s explore both the methods in detail:
HPHT
In the HPHT method of creating diamonds, diamond seeds are put into a sealed vacuum chamber and put through high temperature and high pressure. This leads to chemical reactions with the diamond seed and forms a rough diamond crystal.
The temperature and pressure mimic the intensity that forms diamonds under the surface of the Earth. The temperature ranges between 1300 to 1600°C. The pressure is equal to 8,70,000 pounds per square inch. Once the diamonds are formed, they are sent for cutting and polishing.
CVD
In the CVD method of creating diamonds, diamond seeds or diamond crystals are put into a sealed vacuum chamber. Then carbon gases are introduced into this chamber. The chemical reactions create deposits on the seed, forming the rough diamond.
The CVD method takes about two to four weeks to create diamonds. Once the process is over, the rough CVD diamonds have to go through the process of cutting and polishing. The time required for CVD diamonds to form also depends on the quality of the diamond seed, the size of the chamber, and the number of seeds in a chamber.
Differentiating CVD and HPHT diamonds
Even though CVD and HPHT diamonds are made with the same processes that form diamonds under the earth, there is a difference in properties of both these types of diamonds.
Gemologists and diamond experts can differentiate between the two types of diamonds with the help of special equipment and skills. For instance, they assess the color distribution, pattern of grains, fluorescence color, inclusions, and the inscription on the girdle made by the lab grown diamond manufacturing company.
Here’s a table that shows how you can differentiate between HPHT and CVD diamonds.
| Properties | HPHT | CVD |
| Color distribution | HPHT diamonds display consistent color in the overall diamond. This is due to the process that produces this lab diamond. | CVD diamonds have an even color distribution. That is because the gasses hydrogen and methane spread evenly during the process of the lab diamond formation. |
| Fluorescence | Lab cultured diamonds made through HPHT process, display fluorescence color on their crown or pavilion. | Diamonds grown in labs through the CVD process may or may not display fluorescence color. |
| Inclusions | Lab grown diamonds made via HPHT have dark or opaque inclusions. However, they exhibit a metallic shine under the light. The metals and chemical reactions during the process of production merge with the diamond seed and become inclusions. | CVD diamonds also have inclusions. However, their inclusions are based on the minerals part of their composition. The nature of inclusions in CVD lab produced diamonds is different |
| Inscription on girdle | Diamonds grown in labs have an inscription on the girdle. This inscription mentions the process through which the diamond is made. | Lab produced diamonds made through CVD process have an inscription on the girdle that mentions the diamond process. |
Summing up
When it comes to identifying diamonds, whether mined or lab grown diamonds, or HPHT or CVD diamonds, there are a lot of factors that have to be considered. Diamond experts follow standard methods created by diamond institutions. However, differentiating diamonds also requires special equipment.
The above-mentioned details will help you understand the difference between HPHT and CVD diamonds and also ensure you buy lab grown diamonds more confidently, the next time around!
