Diamond Certificates: IGI, GIA, SGL and What They Mean

A diamond certificate is a short report written by an independent gemological laboratory. It records the measurable qualities of a stone. If you are buying a diamond of any significance, it is the most important piece of paper you will receive.

What a certificate is

A grading report describes a diamond's characteristics: its shape and cut style, measurements, carat weight, colour grade, clarity grade and finish. It is a description by a third party with no stake in the sale. It is not a valuation. It does not say what the stone is worth.

Who issues certificates?

Several laboratories grade diamonds. The names you will meet most often in India are:

• GIA (Gemological Institute of America): the originator of the 4Cs and the international grading system.
• IGI (International Gemological Institute): widely used for diamonds and jewellery, with a significant presence in India.
• SGL (Solitaire Gemological Laboratories): an Indian laboratory used for many Indian-market stones.
• HRD Antwerp: a Belgian laboratory.

We do not rank laboratories here. Different laboratories apply the same scales with differing consistency, so the best practice is to ask which laboratory graded the stone and to look at the report itself.

What a certificate tells you

• The shape and cutting style.
• The measurements and carat weight.
• Colour, clarity and cut grades.
• Polish and symmetry.
• Fluorescence.
• A report number you can verify with the laboratory.

For a full walk-through, read how to read a diamond certificate step by step.

What a certificate does not tell you

• The price or value. Two stones with the same grades can sell at different prices.
• How beautiful the stone is to your eye. Grades describe qualities, but sparkle also depends on cut proportions.
• The jewellery's metal or craftsmanship. The report covers the stone alone.

Is every diamond certified?

Larger diamonds and solitaires are usually certified. Small diamonds used in clusters or pavé, often called melee, are not certified individually. They are described by the total weight and an overall quality range. See melee diamonds: the small stones in jewellery.

How to verify a certificate

1. Note the report number on the paper.
2. Visit the laboratory's website and enter the number to check the online record.
3. Check that the stone's details match the paper: carat, colour and clarity.
4. Many laboratories can inscribe the report number on the stone's edge, the girdle, under magnification. Ask your jeweller to show it.

Questions to ask

1. Which laboratory graded this stone?
2. Can I verify the report online?
3. Is the report number inscribed on the stone?
4. Does the invoice quote the same grades as the certificate?

Our guide to what diamond grading labs actually do goes further into how reports are made.

Common questions

Is a certificate the same as an appraisal? No. A grading report describes the stone. An appraisal states a value, usually for insurance, and is a separate document.

Can a diamond be re-graded? Yes. Some owners send a stone to another laboratory. Grades can differ slightly between laboratories, which is why the report in hand is the one to rely on.

Does the certificate cover the whole ring? No, only the diamond. The metal is covered by its hallmark.

Next step

Our certified diamond jewellery lists its stone details on each page, so you can compare. Start with diamond rings, or book an appointment and ask to see certificates beside the stones.