How to read a report on a laboratory-grown diamond
A grading report is a description of one specific stone, issued by a laboratory that examined it. It carries a number, and that number can be checked against the issuing laboratory's own register, which is the part most buyers never use.
This page walks the report line by line and says plainly which entries are measurements and which are judgments, because the two carry different weight.
The report number
At the top. It identifies this stone and no other. Enter it on the issuing laboratory's verification page and you should see the same report.
Two things to know. A report describes a stone, not a ring: if the stone is already set, the report was issued before setting. And a report number on a website is only meaningful if it is the number for the stone you are being sold, not a specimen shown as an example.
Carat weight
A measurement, taken on a scale. Carat is a weight, not a size.
Two stones of identical carat weight can look noticeably different in size, because how large a diamond appears depends on its shape and how it was cut. A deep-cut stone carries weight where you cannot see it. This is why millimeter measurements matter and are worth asking for. They tell you how large the stone will look on a hand.
Color
A judgment, made by comparison against master stones under controlled lighting. Graded on a letter scale, where the top of the range means an absence of color.
Because it is comparative, color grading is where laboratories differ most from one another. A grade is meaningful relative to the laboratory that issued it.
Clarity
A judgment about internal features, called inclusions, and surface features, called blemishes, made under ten times magnification. The scale runs from stones where nothing is found at that magnification down to stones where features are visible without it.
"Eye-clean" is not a grading term. It describes whether you can see anything at normal viewing distance, which is what most people actually care about, and it does not map neatly onto the scale.
Cut
The one grade that is about workmanship, not the material. It assesses proportion, symmetry and polish, and it is the grade most directly responsible for how a stone behaves in light.
The trade separates that behavior into brightness, fire and scintillation. Cut grading is not offered for every shape: it is standard for round brilliants and less consistently applied to fancy shapes, which matters when you compare two reports for different shapes.
Growth method
A laboratory-grown diamond report states how the stone was grown, by CVD or by HPHT. This is a material fact and it belongs on the report.
The comments section
The part buyers skip and should not. Post-growth treatment is disclosed here, not beside the grades. See the as-grown page for the wording and what it means.
What a report does not tell you
It does not tell you the price, and it does not tell you whether the price is fair. It does not grade the setting. It does not tell you whether the stone suits the hand it will sit on.
It also does not confirm that the stone in front of you is the stone on the report, unless the number matches and, where the stone is laser-inscribed, the inscription matches too.
Questions
Is carat the same as size?
No. Carat is a weight. Two stones of the same weight can look different sizes depending on shape and cut, which is why millimeter measurements are published alongside carat weight.
Which grades are measured and which are opinions?
Carat weight and the measurements are measured. Color, clarity and cut are expert judgments made under controlled conditions, which is why grading can differ between laboratories.
Can I check a report number myself?
Yes. The issuing laboratory publishes a verification page. Enter the number and compare what it returns against the report you were given.
Does every laboratory grade the same way?
No. Standards and strictness vary, so a grade should be read relative to the laboratory that issued it, not as an absolute.
What does the comments section cover?
Disclosures that do not fit the grades, including post-growth treatment.