HPHT vs CVD: Which Lab-Grown Diamond Is The Best?

HPHT-VS-CVD

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Wonder which one is better? HPHT vs CVD? let’s cut to the chase.

There are two types of lab-grown diamonds:

1. HPHT – These diamonds are “as-grown diamonds,” meaning there is no need to use post-growth treatment to enhance the color and clarity of the diamond. What they grow is what we get, just like in nature. This is the good stuff…and it’s much more complicated to grow, so naturally, it involves a higher cost.

2. CVD – In this method, the lab grows low-quality diamonds in masses with low color and clarity. Usually, they show grey or brown colors. Since nobody wants such a diamond, the lab uses post-growth treatment to enhance the color and clarity.

Now you can tell me, “Yaniv, I don’t really care..” and I understand. The problem is that those diamonds are worth half the price of an identical as-grown diamond. Since most customers are unaware of the difference, the sellers try to rip us off and sell it for the same price as an HPHT as-grown diamond.

The following HPHT 1.06 carat E VS1 is sold for $1,750. Most sellers will offer CVD with the same grades for the same price. Don’t buy it, if it’s not as-grown, they should sell it for 30-50% less.

Table of Contents

It wasn’t easy to develop a well-structured method to create diamonds. However, today there are two main successful processes in which lab-grown diamonds are products. This article will cover the difference between these processes, so by the end, you’ll know which one is better for you: HPHT vs. CVD.

Let’s start.

Terms you need to know

Since this topic can be confusing, I want to give you some universal terms in the diamonds industry. You’ll see those terms over and over again in this article. So to make it simple, here they are:

  • As-grown diamond: A lab-grown diamond that was grown and formed like in nature; what the lab grows is what we get. There is no need for another treatment to enhance the beauty of the diamond (Post-growth treatment).
  • Post-growth treatment: A treatment used by labs to enhance the beauty and quality of an existing diamond. In most cases, this diamond was initially formed with low qualities (brown color and inclusions); hence, the lab needs to improve its appearance to make it salable.
  • Treated diamond: A diamond that went through post-growth treatment to enhance its beauty. 

What are lab diamonds?

Lab diamonds also referred to as cultivated, man-made, or cultured diamonds, are grown through a high technological process in a lab environment. The lab mimics the same conditions we can find within the earth’s crust in nature, enabling diamond formation: Hot temperatures and high pressure. As a result, the lab diamond formed has an identical chemical structure and properties to mined diamonds.

What is the HPHT Process to grow lab diamonds?

When looking for a diamond, we need to consider different factors like size, shape, and price. With lab-grown diamonds, we also need to consider the lab method used to create the diamond. Have you heard of HPHT diamonds? Well, here is an explanation of what they are.

HPHT diamonds: What are they?

HPHT is an acronym for high pressure and high temperature. HPHT is a method invented in the 1950s to produce lucrative diamonds. Genuine diamonds can be produced from scratch using the HPHT technique in a controlled environment. Additionally, the HPHT method can enhance natural diamonds’ color to make them brighter, from a yellowish diamond to a colorless one.

HPHT diamonds are considered real diamonds, unlike diamonds simulants such as white sapphire, moissanite, and cubic zirconia. Lab-grown diamonds have the same physical and chemical properties as mined diamonds. This means they will handle the wear and maintain a beautiful look.

How are HPHT diamonds made?

Naturally occurring diamonds take over a million years to form in the earth’s crust when exposed to high pressure and heat. Diamond formation through the HPHT method is faster. The process includes the following steps.

  1. A tiny seed of diamond placed into pure carbon is used to start the HPHT diamond creation process.
  2. From there, the diamond seed is subjected to extreme heat and pressure.
  3. The conditions make the carbon melt, and a diamond starts to build around the seed.
  4. The resulting substance is then cooled to create a diamond.
  5. Finally, the rough diamond is ready for cutting and polishing, set into jewelry like the mined diamond.

How do diamonds receive HPHT color treatment?

The HPHT process is used to permanently improve the color of natural stones and CVD diamonds. When looking at a natural diamond, you might notice a brown or yellow tint; these color hues affect their color grade, for example, M-K colored diamonds. Since most customers are not interested in such a diamond, it would be harder for the seller to sell it. In this case, the seller can decide to use the HPHT process and enhance the color from yellow to colorless (F-D grades). However, since the diamond initially had a lower color, it should be sold for a discounted price (around 50% less).

For example, if a 1.00 carat E VS1 is sold for $8,000, a natural diamond that had an M color and now has an E color should be sold for around $4,000

What diamonds are suitable for HPHT treatment?

There are different types of diamonds today, and most owners would love their jewelry color improved. However, not all types of diamonds are fit for color treatment. Most natural diamonds can take advantage of HPHT color grade improvement, but there are exemptions. All diamonds with a low clarity grade (I1-3, SI1-2) may break or crack during treatment, especially if they have indented natural or cavity.

For a diamond to receive the HPHT color treatment, it should have a minimum clarity grade of VS2, which is a midpoint of the clarity scale. A clarity grade like I3 means the diamonds have many flaws. When exposed to the high pressure and heat of the HPHT process, it might break since the integrity of its structure is already low.

What are the benefits of HPHT diamonds?

You may be out shopping for an HPHT diamond, or you already have an old one and need the diamond to go through HPHT color treatment. Either way, you will reap plenty of benefits from the process. Some of the advantages of HPHT diamonds include:

Permanent effect

Keeping your jewelry sparkly as new is one of the desires of diamond owners. No more worries about your diamond losing its gorgeous color or budgeting for its upkeep. The HPHT color treatment process offers a permanent solution to your diamond.

Genuine diamond

You cannot tell the difference when presented with mined and HPHT diamonds. The HPHT-created diamonds are versatile, strong, and beautiful as naturally grown diamonds. Additionally, the chemical structure and properties are identical to mined diamonds. When you purchase HPHT diamonds, be sure you have high-quality jewelry, and its integrity is intact.

Affordable

Though HPHT-grown diamonds are identical to naturally formed diamonds both chemically and physically, HPHT-created diamonds are less expensive than mined diamonds. This does not mean that their quality and integrity are compromised. The reason why natural diamond is expensive is along the supply chain. Mined diamonds go through different hands of miners, distributors, importers, cutters, polishers, and jewelers. On the other hand, HPHT-grown diamonds go through fewer hands, hence less expensive.

Less pollution

Imagine the environment’s stress when mining natural diamonds from vast earth digging, heavy machinery using a lot of fuel, and disturbance of neighboring natural habitats. All these factors contribute largely to environmental pollution. Lab-grown diamonds do not need mining from deposits hence pose less pollution to the environment.

How to tell if a diamond has been HPHT treated?

The similarities between HPHT and mined diamonds make it hard for an average person to tell the differences. Hence you should refer to the official certification of the diamond. The certificate details will help you know the type of diamonds you are about to purchase.

Expert gemologists working in diamonds grading labs analyze the grades and characteristics of each diamond. From there, they will issue a certificate with detailed information about the diamond for any buyer to access. A reputable lab certificate will indicate whether the diamond was HPHT made or received color treatment through HPHT.

Diamond certifications ensure customers know what type of diamond they are investing in. The certificate also prevents jewelry scammers from taking advantage of customers by execrating grades and hyping the prices. That being said, you should stick to IGI and GIA certificates since they are the most reliable for lab-grown diamonds. Ask for the certificate and shop with confidence.

Generally speaking, some HPHT diamonds show a bluish or greyish tint, even if they are graded as colorless (F-D). I strongly recommend avoiding such a diamond. Moreover, we can see thin lines of metals trapped in some HPHT diamonds, notably lower clarity grades such as SI2-VS2. As long as the diamond is eye-clean, you are safe to pick it.

If you are confused, contact me here and let’s talk.

CVD diamonds: What are they?

CVD means a chemical vapor deposition system used to form lab diamonds. The CVD system starts with a diamond seed, a small part of a natural diamond fit, to undergo high pressure and temperature conditions. This makes it a critical step in the CVD process. It requires choosing the highest and strongest natural diamond to create a lab diamond.

A rough lab grown diamond emerges from the CVD plasma reactor - Picture by Lightbox
A rough diamond emerges from the CVD plasma reactor - Picture by Lightbox

The seed is placed in a vacuum chamber and filled with high content carbon gases, then heated to over 1000 degrees. The high temperatures make the gases turn into plasma. Plasma is a vital ingredient that enables the diamonds layers to build. The result of the CVD process is a lovely stone.

Rows of lab grown diamond seeds that will become lab-grown diamonds
Rows of diamond seeds that will become lab-grown diamonds - Photo by Lightbox & Forbes

How to know if a lab grown diamond is CVD?

Using your naked eye to tell which process was used can be difficult. The CVD process, like the HPHT, produces real diamonds similar to those mined naturally; hence hard to differentiate.

However, the plasma that forms to build the CVD diamond, layer by layer, can cause a hazy, milky, or oily appearance. You can see it when using a good magnification tool, such as this one.

In most cases, CVD diamonds have a brownish or greyish tint. For that reason, the labs use HPHT post-growth treatment to enhance the color and clarity.

The safest way to verify if a diamond is CVD is to ask for its certificate. Look for the comment section and check whether the lab mentions it’s CVD or HPHT, as-grown or if there are indications of post-growth treatment.

CVD diamond certificate

ALERT! With CVD diamonds, the lab does not always mentions if there was a post-growth treatment involved in the process. If you buy a CVD diamond, buy only those with certificate that states clearly one of the following options:

  1. As Grown – No indication of post-growth treatment.
  2. This Laboratory Grown Diamond was created by Chemical Vapor Deposition (CVD) growth process and may include post-growth treatment.

CVD diamond price

As we covered, most CVD diamonds are produced with low color and go through post-growth treatment. Such a diamond is worth 50% less than an HPHT as-grown diamond. However, since most customers are unaware of the difference, most sellers offer both HPHT and CVD diamonds for the same price.

HPHT vs CVD: Which one is better?

CVD is not better than HPHT if both diamonds are as-grown and share identical grades. That being said, as far as I know, currently, only one lab in the world has the technology to produce untreated CVD diamonds. You can find those CVD as-grown diamonds on James Allen, mostly in oval, pear, and princess shapes.

Regarding other labs, since they use post-growth treatment to enhance the beauty of the CVD diamonds, I recommend sticking to HPHT as-grown diamonds. Remember, CVD-treated diamonds should be sold for half the price of as-grown HPHT diamonds. Don’t fall for it! Unless you have a tight budget and find an excellent deal on CVD. I know it’s confusing, so feel free to reach out here and let’s talk.

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