Lab Grown Diamonds: What’s the Difference between CVD and HPHT?

Lab Grown Diamonds:
What’s the Difference between CVD and HPHT?
Dec 21, 2022

The lab grown diamond deep dive you’ve been searching for.

Lab grown diamonds are growing in popularity. As we enter a new year, we predict that lab grown diamonds will continue to be a client preference for rings, bracelets, necklaces, and all fine jewelry!

A lab grown diamond is a real diamond, having the same chemical and physical composition as natural diamonds do. However, instead of being formed in the earth over millions of years, lab grown diamonds are- you guessed it- created in a lab in a much shorter time frame. Learn more about lab grown diamonds here.

If you are considering purchasing a lab grown diamond engagement ring, you may be interested in learning more about their origin and what makes them unique. One of the deeper questions our team at Yadav hears often when it comes to lab grown diamonds is what the difference is between CVD and HPHT lab grown diamonds.

From left to right: CVD, HPHT, Natural Diamond. Credit: GIA
From left to right: CVD, HPHT, Natural Diamond. Credit: GIA

Whether you love to get deep in the learnings or if you just want to know the basics, we’re summarizing the two techniques for your next diamond purchase. In this article, we are breaking down the key differences between CVD and HPHT lab processes and their effect on diamond quality and appearance.

Chemical Vapor Deposition Diamonds

The process of Chemical Vapor Deposition (CVD) was created in the early 1980s but has recently become the more common approach. This methodology imitates how diamonds form in natural gas clouds. In this process, a high carbon chemical mixture of methane and hydrogen rains down onto a diamond crystal in layers. The longer the crystal sits in this chamber, the bigger it gets as the carbon adheres to the crystal.

The CVD process produces Type IIA diamonds which are quite rare for even natural diamonds. Type IIA diamonds are the most chemically pure diamonds. The CVD method offers a much more efficient way of growing diamonds as they do not need the intense conditions that HPHT diamonds do. One thing you might consider is that CVD diamonds ame more cost-effective in production.

HPHT synthetic crystals grown by Jinan Zhongwu New Materials Company Ltd. of Shandong, China. Credit: GIA
HPHT synthetic crystals grown by Jinan Zhongwu New Materials Company Ltd. of Shandong, China. Credit: GIA

The HPHT method was introduced in the 1950s. Diamonds typically need pressure, high temperatures, and time. The HPHT process emphasizes the first two, while cutting the time needed to a fraction. In this process, a crystal seed is exposed to carbon and metallic flux at high pressure and temperatures- enough to replicate the natural process in the earth. As the carbon melts around the seed then cooled, a diamond is formed.

HPHT diamonds have a few unique possibilities in the end raw product because of the process. Some may have a yellow hue since they are often exposed to nitrogen others may have a blue hue from boron exposure. They also tend to have metallic inclusions, making it possible to be magnetic.

Are CVD or HPHT diamonds better?
HPHT synthetic crystals grown by Jinan Zhongwu New Materials Company Ltd. of Shandong, China. Credit: GIA
This chart shows the different methods of diamond growth and an example of their rough form. Credit: GIA

Diamonds grown with the CVD or HPHT method are all real diamonds! Both methods produce diamonds that are physically, optically, and chemically identical to natural diamonds although they may have unique characteristics before they are cut and polished as seen in the figure above. Both types are made of pure carbon and create the same hardness. To the naked eye, there are no clear differences between a CVD and HPHT diamond and the price for each option are very similar.

Whichever method is used in creating your diamond of choice, a seasoned jeweler will ensure that it has the sparkle and shine that you expect. Still not convinced? Here are a few more reasons to consider a lab grown diamond.

Almost every style at Yadav can be designed with natural or lab grown diamonds, so we are happy to work with you if you are looking to learn more or start designing a piece. Reach out to our experts or schedule an appointment in our showroom.

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