CVD diamond grading and reports
How CVD diamonds are graded, what the report tells you about growth method and treatment, and how to check a report yourself.
Same 4Cs, extra lines
CVD diamonds are graded for carat, colour, clarity and cut like any diamond. A lab-grown report adds what matters to a trade buyer: that the stone is laboratory-grown, the growth method (CVD or HPHT), and whether there are indications of post-growth treatment.
What to read on the report
| Line | What it tells you |
|---|---|
| Laboratory-grown | Confirms it is not a mined diamond. Required for honest selling. |
| Growth method | CVD or HPHT. Useful if your customers ask, or for matching goods. |
| Treatment comment | Whether the lab found signs of post-growth treatment, or "as grown". |
| Inscription | The report number laser-inscribed on the girdle, often with an "LG" prefix. |
| Measurements & weight | Match these to the stone in your hand. |
Clarity in CVD stones
CVD stones can show small dark inclusions of non-diamond carbon and, under magnification, faint growth layering or strain. These are graded like any inclusion. Good growers sort them out before polishing.
How to check a report
- Find the report number on the paper or PDF, and on the girdle inscription under a loupe.
- Look it up on the lab's own site: IGI report check or GIA report check.
- Compare carat weight, measurements and grades with the stone and the invoice.
Lab logos on a supplier's website are not company certifications. They only mean the supplier sends stones to that lab. Check each report.
Questions
Do CVD diamonds come with certificates?
Most traded CVD stones above about 0.30 ct come with a grading report from a lab such as IGI or GIA. Small melee is usually sold in parcels without individual reports.
Does the report say the stone is CVD?
Lab-grown reports normally state the growth method and whether post-growth treatment was detected. Check the comments section.
Can a CVD diamond be told apart from a mined one?
Not by eye. Gem labs identify lab-grown diamonds with spectroscopy and fluorescence imaging, which is why a report matters.