Laboratory-grown diamonds are often grouped into one category, but they are produced by more than one growth method. The two primary methods used for gem-quality material are chemical vapor deposition, or CVD, and high pressure high temperature, or HPHT. The methods create different growth environments and may leave different features that trained laboratories can identify.
For a shopper, the method is background information - not a substitute for evaluating cut, appearance, measurements, and disclosure. Neptunes Jewelry offers natural and laboratory-grown diamond options within its custom engagement-ring process, allowing clients to compare individual stones and reports rather than selecting by acronym alone.
HOW HPHT GROWTH WORKS
HPHT growth uses very high pressure and high temperature to create conditions in which carbon dissolves and crystallizes onto a diamond seed. The process is conceptually related to the conditions under which natural diamonds form deep in the Earth, although laboratory equipment controls the environment and growth period.
HPHT-grown diamonds can be colorless, near colorless, or colored depending on growth conditions and impurities. Metallic inclusions or characteristic growth features may occur, but finished appearance varies widely. A well-cut HPHT diamond should be judged as an individual stone.
HOW CVD GROWTH WORKS
CVD growth takes place in a lower-pressure chamber containing carbon-bearing gas. Energy breaks the gas molecules apart, and carbon deposits layer by layer on a diamond seed. Growth may occur in stages, and the crystal can show layered or striated features that laboratories use during identification.
Some CVD-grown material is subjected to post-growth treatment to improve color or other appearance characteristics. Treatment does not mean the stone is imitation, but it should be disclosed accurately and reflected in the report when applicable.
CVD VS. HPHT AT A GLANCE
| Question | CVD | HPHT |
| Growth environment | Carbon-bearing gas deposits material on a seed in a chamber | Carbon crystallizes on a seed under high pressure and temperature |
| Growth pattern | Often layered growth features | Often sector-based growth features |
| Possible post-growth treatment | May be used to modify color | May be part of growth or used to modify other material |
| Visible quality | Ranges widely; method alone does not predict beauty | Ranges widely; method alone does not predict beauty |
| Identification | Requires trained laboratory testing | Requires trained laboratory testing |
GROWTH METHOD DOES NOT REPLACE THE 4CS OR VISUAL REVIEW
A CVD diamond is not automatically better or worse than an HPHT diamond. Both categories include stones with different color, clarity, proportions, transparency, and cutting quality. Compare the actual diamond's brightness, contrast pattern, face-up dimensions, and report.
Report formats and terminology can change over time and differ among laboratories. Use the report number and issuing laboratory's current verification tools, and read the origin and treatment statements rather than assuming every report uses the same grading framework.
POST-GROWTH TREATMENT AND DISCLOSURE
Post-growth treatment may be used to alter color or reduce the visibility of certain growth-related features. The key issue is transparent disclosure. Ask whether treatment was detected, how the report describes it, and whether the seller's description matches the laboratory document.
- Confirm that the stone is clearly identified as laboratory-grown or laboratory-created.
- Read comments about growth method and treatment, if the report provides them.
- Verify the report number directly with the issuing laboratory.
- Do not accept environmental or ethical claims without specific supporting information.
- Compare price, appearance, and service based on the actual stone rather than the growth acronym.
CAN CONSUMERS IDENTIFY CVD OR HPHT BY EYE?
Not reliably. Laboratory identification may use spectroscopy, fluorescence imaging, magnification, and other specialized testing. Visual appearance alone cannot consistently distinguish natural, CVD-grown, and HPHT-grown diamonds.
This is why clear seller disclosure and a reputable laboratory document are important. A report does not choose the stone for you, but it establishes material identity and records relevant grading or descriptive information.
FAQ
1. Are CVD and HPHT stones real diamonds?
- They are laboratory-grown diamonds, not diamond simulants. They share diamond's fundamental crystal structure and material properties, but their laboratory origin must be disclosed.
2. Is one growth method more valuable?
- Growth method alone does not establish value. Market conditions, size, appearance, quality, report, treatment, and seller services all influence price.
3. Can CVD diamonds receive HPHT treatment?
- Some CVD-grown diamonds may undergo post-growth treatment using high-pressure, high-temperature conditions. The laboratory report should be reviewed for treatment information.
4. Can a jeweler tell the method with a loupe?
- Certain features may provide clues, but reliable identification commonly requires specialized laboratory equipment and trained analysis.
5. Does CVD or HPHT tell me how much the diamond will sparkle?
- No. Sparkle depends mainly on the individual stone's cutting, transparency, facet pattern, and viewing conditions.