Source and scope
What GIA found. What I would check.
Source and scope: This is a GIA Gems & Gemology lab note, not a YDG client result. GIA did the testing. I explain what I would ask when an old report and a current listing tell different stories.
- Earlier weight
- 16.41 carats
- Later weight
- 15.73 carats
- Publication
- Spring 2024
Two laboratory visits
The grades stayed the same while other facts changed.
GIA had previously examined a 16.41 carat G color, VVS2 CVD grown diamond with no indication of post growth treatment. The stone was later resubmitted at 15.73 carats. GIA's new testing showed HPHT treatment. Its color and clarity grades stayed the same. GIA said repolishing after treatment could partly explain the 0.68 carat weight loss.
| Earlier record | Later examination | Buyer question |
|---|---|---|
| 16.41 carats | 15.73 carats | Do the current measurements and weight match the listing? |
| No post growth treatment indicated | HPHT treatment detected | Does the current disclosure match the current stone? |
| G and VVS2 | G and VVS2 | Are unchanged grades hiding a changed history? |
Read GIA’s earlier 2022 examination. It records the diamond before its later treatment.
G and VVS2 stayed on the page. The weight and treatment history changed. If you only saw the first report, you would miss both.
GIA checked more than the growth pattern.
Left: before HPHT. Right: after. GIA’s cathodoluminescence views showed no observable differences in the growth features. Other tests still established treatment. I want the full current lab findings before trusting an old report.
The paired cathodoluminescence images show the same diamond before HPHT treatment on the left and afterward on the right. GIA found no observable differences in these views. The dark dots relate to lattice dislocations, and the growth interfaces remained unmodified. Other laboratory evidence established treatment. These images neither compare the stone’s ordinary body color nor account for all of its weight loss.
Current evidence
Make the listing, report, and video describe the same stone.
Ask for the full current report or assessment, report date, stock number, inscription, and present measurements. If there are older documents, ask why the stone was reexamined or recut. A newer report can be perfectly reasonable. A mismatch without an explanation is where I stop.
The lab grown report guide gives a broader checklist. Our GIA Premium and Standard guide explains the current GIA lab assessment system. This case came before that change. Read its reports using the terms GIA used at the time.
The laboratory evidence changed when the headline grades did not.
The G and VVS2 grades stayed put. These laboratory measurements changed. GIA compared the same diamond before and after HPHT treatment using two excitation wavelengths. The changing spectral features helped establish the treatment. They do not rank the diamond’s beauty or price.
GIA compared the earlier 16.41 carat state and the later 15.73 carat state using 514 and 457 nanometer excitation. The study reports reduced nitrogen vacancy features and increased silicon vacancy response in the 514 nanometer spectrum. In the 457 nanometer spectrum, some features disappeared while others developed after HPHT treatment. The spectra are scaled and offset for comparison. The weight, treatment evidence, and current documentation therefore matter even when color and clarity grades match.
The limits of the case
GIA tested the stone. It did not report a sale.
GIA did not report a retail sale or say that a seller misled anyone. The treatment finding alone does not tell you whether the stone is a good buy. Ask whether the report describes the diamond in front of you now.
Your purchase
What I would ask before buying.
A newer examination can be completely reasonable. What matters is whether the seller can connect the current stone with the current documentation.
- Compare current weight and measurements with the listing.
- Read the latest report date and treatment disclosure.
- Ask which images show the stone in its current condition.
- Request an explanation for older reports or a changed inscription.
Buyer questions
Your questions, answered
Is an older report always invalid?
No. Check whether the stone has changed since grading. If its weight, measurements, or treatment history changed, ask for current documentation.
Did the treatment improve the color in this GIA case?
GIA reported no observable color improvement. The color and clarity grades stayed the same.
Can a product video show HPHT treatment?
No. A video helps me judge the look. GIA needed laboratory testing to find the treatment. Ask for the current report as well as the video.