HPHT vs. CVD?

 

HPHT vs. CVD | Which lab-grown diamond growth method should you choose? 

HPHT = High Pressure & High Temperature

CVD = Chemical Vapor Deposition

Lab-grown diamonds are grown in laboratories using two growth methods – HPHT and CVD. We won’t focus here directly on the growth method itself, but rather on what should matter to you, as a customer, when choosing a lab-grown diamond, and why. This is our subjective opinion based on our own experience. 

 

CVD method

We recommend choosing the CVD method for smaller stones that are not certified (IGI, GIA). Lab-grown diamonds grown using the CVD method are detected as “diamond” by testers, while small HPHT stones are detected as “moissanite”. This makes it difficult to prove whether a stone is moissanite (SiC – silicon carbide) or a lab-grown diamond. A set stone would have to be removed from the jewellery piece, which is of course an unwanted intervention and would damage an already finished piece of jewellery. 

On the other hand, you should be careful and ask sellers of natural diamonds for confirmation that the stones set in their pieces are not lab-grown. These are indistinguishable from natural diamonds, and once set in a piece of jewellery, the customer has no way of telling them apart. You cannot tell a natural diamond from a lab-grown one even when they are not set in jewellery, and it comes down to the trustworthiness of the manufacturer as to which diamonds they use. The only difference between small natural and lab-grown diamonds is the price. Small natural diamonds do not have certification or a girdle inscription, which all larger certified lab-grown diamonds have. 

 

HPHT method

For larger certified lab-grown diamonds, on the other hand, we recommend choosing the HPHT growth method. In our view, these are lab-grown diamonds that achieve higher quality compared to those produced solely by the CVD method. CVD lab-grown diamonds often reach a lower colour grade (G-H) and are then “upgraded” using the HPHT method by one to two grades = a G-H lab diamond produced by the CVD method can, after HPHT treatment, achieve a higher colour grade. HPHT is also a method that faithfully replicates the conditions under which natural diamonds form deep underground. What can be confusing, however, is that lab-grown diamonds produced by the HPHT method may be detected as “moissanite” by testers. This is caused by the presence of tiny metallic particles, which affect the testers. On the other hand, these lab-grown diamonds carry a unique number on the girdle, which matches the number on the certificate you receive with the lab-grown diamond. The customer can then quickly  and easily verify information about the colour, clarity, cut and other properties either directly from the certificate, or on the IGI website (Verify Your Report – IGI). There you can also download the certificate in PDF format at any time. 

The certificate also states whether the stone may contain additional treatments (for the CVD method), or that it contains no additional treatments (HPHT). This information is listed below the basic information about the lab-grown diamond. 

Summary: 

For smaller, uncertified stones, we recommend the CVD method. 

For larger, certified stones, we recommend HPHT lab-grown diamonds.

 

Note:  

If you are also buying natural diamonds, the seller should be able to measure, on request, whether the diamonds in, for example, your ring are actually natural, since small lab-grown diamonds do not have a laser inscription number on the girdle, and standard diamond testers also detect them simply as “diamond”. Special testers are therefore needed, ones that can already distinguish a lab-grown diamond from a natural one. 

We have a selection of more than 50,000!! diamonds for you to choose from, so we firmly believe we will find the right diamond for you. We actively monitor our competitors’ prices and can say that we offer both lab-grown and natural diamonds at the best prices on the market. 

If you are still undecided, send us an inquiry and we will promptly send you an offer you can compare with no obligation. 

We look forward to hearing from you soon! 

If you have any questions about lab-grown & natural diamonds, feel free to write to us at: info@laboratornidiamanty.cz 

Team ULTIMATE-GEMS s. r. o.