When looking at lab created diamond you may see cvd vs hpht labels, but what do they mean? Both create the same type of diamond crystal, though the growth method is slightly different from a chemical perspective
What’s the difference between these two diamond formation methods? And, how might each affect the value and appearance of your created diamond? We consider these topics, as well as what to think about when looking at two similar lab diamonds.
What Makes a Laboratory Diamond a Diamond?
A diamond consists of carbon atoms in an organized crystal matrix, which defines its appearance and desirable characteristics. These properties define a naturally occurring diamond in the rough form, but not the location or source of the stone
Unlike a cubic zirconia or moissanite, a laboratory diamond is indeed a diamond, though not mined
A crystal matrix can possess unique qualities based on method of creation, and the unique properties present in a laboratory diamond are revealed through inspection. With a few exceptions, these qualities are not typically seen in a finished polished stone, making visual distinction difficult.
Overview and Comparison of Lab Grown Methods
A technician begins the CVD (Chemical Vapor Deposition) process by introducing a small diamond seed with carbon gas (typically a mixture with hydrogen gas) into a chamber
Upon application of an appropriate energy source, the gaseous carbon becomes activated and deposits itself onto the seed in layers until a crystal has formed.
The process takes place under high temperature, but the pressure is considered lower than what is seen in the HPHT methodology. As a general rule, variations taking place during crystal growth can impact the results. Some CVD stones demonstrate a characteristic brownish tint, which may be addressed during secondary processing. This is not a universal trait, and some stones do not need the additional treatment. The method and potential treatments both influence the value, which is why the finished stone is important to consider.
In the case of HPHT (High Pressure High Temperature) methodology, a technician begins with a diamond seed, carbon source, and a catalyst (typically metal). The combination is placed inside of a press and heated until the carbon begins to melt.
This particular arrangement mimics the natural diamond formation process, although on a smaller scale and with reduced duration. Metal tends to mingle with the crystal lattice, introducing desirable qualities. Each crystal is unique in terms of coloration and fluorescence. As will be discussed later, this is a consideration when looking at two similar stones, but it does not automatically dictate that one is lower quality than the other.
Differences Between CVD and HPHT Lab Diamonds
Appearance and Sparkle
Both of these methods generate a sparkly diamond when cut and polished correctly, but how would you determine which resembles a natural diamond more? In many cases it comes down to the cut and quality rather than the method of formation.
A smaller or lower cut quality, even in a higher color grade, may actually appear to sparkle less than a higher cut quality in an ideal cut. Watch videos of the cut and examine whether or not the light moves across and within the stone. Always see the diamonds in the same lighting and try to compare real cut quality and symmetry rather than color, clarity, and shape. Unless you are looking at very similar stones, it is easy to become misled.
Color and Additional Treatment
Both sets of circumstances (natural and laboratory created) generate a broad range of results. A CVD diamond can possess a characteristic tint that is removed via additional HPHT treatment.
A diamond of this type has been grown using the CVD method, but has seen an additional treatment after the fact. This is not an automatic indication of lower quality, but is important to consider when thinking about which lab created diamond deals represent the most value.
Clarity and Internal Features
A CVD diamond may exhibit characteristic graining, and a HPHT diamond can reveal tiny metallic flecks within its crystal lattice. These features are typically not visible to the naked eye, and are more common to see under magnification or microscopic inspection. Unless specified, a clarity inspection should involve determining if any inclusions are visible with the naked eye and what effect they might have on sparkle and light reflection. Where these things fall in the category of normal or unusual can play an important part in value and appearance considerations, although this varies between people.
Price and Value
There are no absolute value rules when it comes to the discussion of lab created diamonds. The carat weight, color grade, clarity, cut quality, cut shape, and availability all play a role. Even stones of the same shape and comparable color grades, clarity, and cut can have noticeably different prices depending on the seller, and the difference between a higher and lower quality cut can appear significant at retail price when compared to a laboratory-grown alternative.
Compare similar diamonds when looking for a deal. While lower priced options can be appealing, ensure that you are seeing accurate cut quality and documentation regarding the sparkle and light performance characteristics, as well as the consumer return policy on the item in question. There is often a considerable difference between the stated price, shipping costs, sales tax, setting, and inspection or return policies. Always verify that you know what is included in the advertised price.
How to Compare Two Stones Before Buying
Avoid a practice of evaluating the certificate first, and then the diamond second. Review the cut and quality first, and then move on to color (ideally in a neutral setting), followed by clarity considerations and microscopic inspection of any photos offered for viewing. See all diamonds at the same time and evaluate how each would appear to you in terms of sparkle, light movement and performance, and appearance. Consider the carat weight and actual size of a particular diamond, ensuring that you are seeing how the weight relates to the overall size of the stone. Review the report number, laboratory origin claim for clarity, and treatment documentation if available. Review return policies before purchasing.
Use these same diamond buying considerations for any other type of manufactured or laboratory created diamond, which can greatly improve the likelihood of satisfaction after making a purchase.
Diamond Buying Considerations: An Example
Assume there are two round shape diamonds available. The carat weight is approximately the same for both, but one is CVD laboratory created and the other HPHT laboratory created.
Diamond A has an attractive brilliance display with a high quality cut (excellent grade), whereas Diamond B has lower overall brilliance and a superior clarity grade. Based on these factors, you may find that the lower clarity grade of Diamond A outweighs the lower quality cut of Diamond B, or you may see the reverse, and both stones appear similar under the same viewing conditions. If the second appears more attractive, but has a higher price, consider the overall reasons behind the disparity before making a choice.
What’s Most Important: Appearance, Documentation, or Cost?
In terms of the cvd vs hpht discussion, the relevant consideration is not whether one method creates higher quality results, but what each can provide in the way of value. This is a personal consideration that should be addressed individually, but it involves documentation, appearance, and price.
Review the Report, Not Just the Product Page
An outside agency can assess certain characteristics, including the weight, shape, width, length, color grade, clarity grade, and cut grade, when reviewing a diamond certificate to support the description and photographs. In some cases, these reports identify the growth type and post-growth treatment with specific disclosure.
When reviewing a report, pay close attention to what is said and what might be missing. Not every certification company provides the same details, and some report services do not identify the growth type or additional treatments for various reasons.
Ensure that each report corresponds to the product and view the entire document. Inspect photographs and video when available, watching for bow-tie effects within elongated shapes and dark spots or inclusions that might be problematic. While a report confirms certain qualities, it cannot show the effect of any diamond on a person’s hands.
Consider the Entire Ring, Not Just the Center Stone
An engagement or wedding ring involves additional factors. The prongs can be positioned in a variety of ways within a band, and this impacts appearance and comfort. A lower color grade may appear significantly different in yellow metal versus white, even with minimal variation within the same grade. Be honest with yourself about an acceptable color grade and the intended appearance. Set an upper limit for a budget for the ring itself and any associated modifications or adjustments.
Frequently Asked Questions
Is One Growth Method Better for Engagement Rings?
Each method produces desirable diamonds for engagement rings, and each must be reviewed on a case by case basis.
Can You Tell CVD and HPHT Diamonds Apart by Eye?
An expert can inspect a stone and identify certain characteristics that indicate one creation method versus another, but the average eye does not register the changes that take place during laboratory diamond formation. This means it is not possible visually to distinguish between them on the basis of creation method.
Does HPHT-Treated Mean the Diamond Was Grown by HPHT?
No. A laboratory diamond has grown using one method, but has seen an additional treatment after for appearance reasons. Always see what kind of treatment a diamond has seen and why.