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What is an HPHT Diamond?

by Willyou.net * Mar 26, 2022

Key Takeaways

  • HPHT stands for High Pressure High Heat – one of two processes used to create lab grown diamonds for use in jewelry.
  • The process of HPHT is designed to mimic the natural forces at-play in the earth’s mantle, but at a rapidly accelerated rate.
  • This process allows producers to create many lab grown diamonds in a very short span of time, which is one of the reasons why these stones have a much, much lower value than natural diamonds.
  • Lab grown diamonds can be referred to as real diamonds, but they do not offer the same long-term investment potential or cultural value as nature-created diamonds.
What is an HPHT Diamond

These days, the diamond world is divided between two separate interests: natural, earth-created diamonds – rare, valuable, and totally unique – and lab grown diamonds, created to fulfil a demand for cheaply manufactured and easily acquired gemstones. It is not quite a tale of two halves, since so many gemologists, jewelers, institutions, and collectors continue to focus their attention solely on natural diamonds, but they have continued to grow more prominent in recent years.

There are plenty of reasons for this, but also plenty of reasons why so many people are uninterested in the trend for lab grown diamonds. Sure, they’re a lot cheaper, but they’re also a lot less valuable. Yes, they’re structurally and visually similar to natural diamonds, but they’re also missing their rarity, not to mention their emotional and cultural significance. And, finally, while they are a sustainable alternative, they’re not quite as eco-friendly or socially conscious as some marketing campaigns would have you believe.

 But, still, it always pays to understand the full picture before you make a commitment – and, if you’ve seen anything online about lab grown diamonds, you’ve likely come across the phrase ‘HPHT diamonds’ already. Here are the basics.

HPHT Diamonds

Everything you need to know about the diamonds themselves.

Is HPHT a lab diamond?

Yes, HPHT diamonds are lab grown diamonds.

The main alternative to HPHT for lab growing gem quality diamonds is known as CVD, or Chemical Vapor Deposition.

There are other techniques out there capable of creating diamond in a lab setting, but HPHT and CVD are the only two currently used to create commercial stones for the mass jewelry market.

What are HPHT diamonds?

HPHT is an acronym for High Pressure High Temperature, which itself refers to one of the most popular techniques for creating diamonds in a lab.

If that sounds familiar, it’s because the entire process is designed to replicate the conditions deep under the earth’s mantle, and to mirror how natural diamonds are created in a controlled setting – and, in essence, in a way that can be repeated over and over again, according to market demands.

How HPHT Diamonds are Made

HPHT requires the use of a ‘diamond seed’ – a single crystal diamond. These diamond seeds are as small as they sound, but play a vital role in the process, and create a ‘base’ on which carbon atoms are able to precipitate. Temperatures exceed 1400°C (2552°F), and the process will go on for days or weeks – a far cry from the billion year process natural diamonds went through.

After forming within the lab, the diamonds are removed, cut, and polished like any other diamond.

Are HPHT diamonds real diamonds?

Yes, HPHT diamonds are real diamonds, but they’re not natural diamonds.

Lab grown diamonds (whether HPHT or CVD) are technically referred to as ‘real diamonds’, since their chemical makeup and optical properties are the same as natural diamonds. There are, however, many differences between the two.

HPHT diamonds are not diamond simulants – a group of gemstones that includes cubic zirconia and moissanite – and are considered to be real.

How can you tell if a diamond is HPHT?

While made from the same basic elements, the internal structures of HPHT and natural diamonds typically differs enough for gemologists to sort one from the other.

Before a diamond has been cut, you can identify the ways in which a diamond has grown by looking at the shape it naturally took. Most natural diamonds form in a shape featuring eight triangular sides, resembling resembles two pyramids placed base to base. This is known as an octahedron. Not all natural diamonds form in this shape, but it is referred to as diamond’s crystal habit, meaning it’s characteristic of substance.

By contrast, HPHT diamonds tend to grow in different shapes, meaning that their internal structure differs from that of a natural, earth created diamond. This isn’t something you (or anyone else) will be able to see without specialist equipment, however – something that can work in lab grown diamonds’ favor when shoppers are on the fence.

Do HPHT diamonds test as moissanite?

No, but moissanite can pass some diamond testers.

Moissanite is formed of silicon carbide, not carbon, and is a much better conductor of electricity than diamond (both natural, and lab grown). For this reason, it is possible to distinguish between the two.

Besides, there are other ways of identifying a real diamond from a simulant. Read our guide to moissanite vs diamond vs cubic zirconia if you want to find out more about this. 

Which is better HPHT or CVD diamonds?

CVD is a much less intensive process, meaning that it doesn’t need to reach such high temperatures or pressures in order to yield a diamond.

If you really want to know which is best for you, however, we would only ever recommend you invest in a natural diamond for your engagement ring. In terms of long-term financial and sentimental value, they’re unbeaten.

HPHT Color Treated Diamonds

High pressure high heat can also be used to ‘correct’ instances of undesirable color in diamonds. It is a permanent procedure, and highly intensive. Only diamonds with a very high clarity grade can be considered suitable for HPHT color treatments, since the highly pressurized conditions can easily shatter or destroy an otherwise valuable diamond.

In most cases, Type IIa diamonds are subjected to HPHT treatments, since they are among the most valuable. Generally, however, enhancements of any kind are regarded by the diamond community as undesirable, and aren’t pursued all that regularly.

Our Summary

Lab grown diamonds have seen a certain amount of interest over the last few years but, for the most part, their influence on the diamond industry has remained on the margins. While they are physically and visually identical to natural diamonds, they also represent polar opposites in so many ways.

From the fact that they are not (and never will be) a rare resource, to the fact that they do not offer the same cultural and emotional significance to collectors and first-time buyers, lab grown diamonds are lightyears from unseating their natural, earth-grown counterparts.