What IGI actually does
The International Gemological Institute is an independent gemological laboratory. It receives a loose diamond, grades it against consistent standards, issues a report, and returns the stone. IGI does not sell diamonds, does not price them, and has no stake in whether a given stone is bought.
For lab-grown diamonds, IGI is the most widely used lab in the industry. Its reports specifically confirm origin as laboratory grown, and its grading of cut, colour, clarity, and carat is respected worldwide.
Why an independent report matters
Anyone can claim a diamond is G colour, VS2 clarity. A grading report from an independent lab is the difference between a claim and a verifiable fact. It puts the seller, the buyer, and the stone on the same page, in writing.
Every diamond in the Harlow Vault ships with its full IGI report, and the report number is inscribed on the girdle so you can match the stone in hand to its paper.
How to read the report, line by line
Shape and cutting style
The outline (round, oval, cushion, etc.) and the faceting family (brilliant or step). This defines what the rest of the report is grading.
Measurements
The stone's dimensions in millimetres. For a round, it's diameter x depth. For fancy shapes, length x width x depth. This is the stone's real footprint on the finger.
Carat weight
The exact weight, reported to two decimal places. A 0.98 and a 1.00 look identical face up but often price very differently — a small quirk of the market worth knowing.
Colour grade
D through Z on the standard scale. See our colour guide for what that means in real life.
Clarity grade
FL, IF, VVS1, VVS2, VS1, VS2, SI1, SI2, I1-3. Graded under 10x magnification, not by eye.
Cut grade
For round brilliants, IGI issues Ideal, Excellent, Very Good, Good, Fair, Poor. Not always assigned for fancy shapes.
Polish and symmetry
How cleanly the facets are finished and how well they line up. Excellent or Very Good on both is what you want.
Fluorescence
How the stone responds to ultraviolet light. None to Faint has no practical effect. Medium and Strong Blue can help colour appear whiter in daylight but occasionally cause milkiness in higher clarities.
Proportions diagram
A cross-section showing table percentage, depth percentage, crown and pavilion angles. This is where you can tell how well the stone was cut for light.
Clarity plot
A map of where inclusions sit. Useful for judging whether an SI1 will look clean face up or whether an inclusion sits under a prong.
Origin
For lab-grown stones, the report explicitly states the diamond as laboratory grown and identifies the growth method (HPHT or CVD).
Laser inscription
A tiny report number etched on the girdle. You can match the stone in hand to the report with a loupe.
Verifying the report yourself
Every IGI report has a unique number. You can look it up on IGI's public report checker to confirm the report matches the stone. That lookup shows the same grades on your paper report, so you can be sure nothing has been altered.
If you would like to see the report for a stone before purchase, just reach out — we're happy to send the full PDF.
What a report does not tell you
A report grades the stone against a standard. It does not tell you how the stone looks in your hand, how it wears with your skin, or whether it is beautiful. Two stones with identical reports can look quite different in person, especially in the SI clarity range.
That is why we review every stone in person before it enters the Vault, and why the photos and videos on each listing are of the actual stone, not a stock render.