You have tested your diamond at home and the result looks off. That can be unsettling, but the issue is usually the testing method rather than the diamond itself.
Below, we cover how to verify an IGI certificate, how to find the IGI report number inscription on your stone, and why low-cost handheld testers often give misleading readings.
In this guide
How to check an IGI certificate
Start with the grading report. Every IGI report has a unique number that you can look up on IGI's official verification page.
When you pull up the report, compare these details against your order or listing:
- Report number
- Shape and cutting style
- Carat weight
- Colour and clarity grades
- Measurements and proportions
Worth noting: carat weight, colour, and clarity cannot be confirmed at home. Verifying those grades properly requires a professional gemologist with laboratory equipment.
If the details on the report match your order, that is the most reliable confirmation your diamond is correctly certified.
How to find the IGI certificate number on a diamond
Most certified diamonds have a microscopic laser inscription on the girdle (the thin outer edge of the stone). You will not see it with the naked eye.
To find it:
- Use at least 10x magnification (loupe or microscope)
- Use bright, directional lighting
- Rotate the stone slowly to catch the inscription angle
- If mounted, inspect areas of the girdle not covered by claws or bezel
Not seeing it straight away does not mean something is wrong. The inscription is tiny, and visibility depends on the angle, lighting, and quality of your magnification.
Why cheap handheld testers are often inaccurate
Handheld diamond testers have their place, but low-cost devices are known for inconsistent results. They can produce false negatives, particularly with mounted stones or when the probe does not make clean contact.
An unexpected reading is a reason to re-check your method, not a reason to panic. A single result from a budget tester is not reliable evidence on its own.
Common causes of unreliable readings:
- Low battery or poor calibration
- Probe touching metal instead of only the stone
- Stone surface residue (oil, lotion, dust)
- Incorrect probe angle or unstable pressure
- Temperature and environment effects on low-end units
Before worrying, try this:
- Make sure the device is fully charged and calibrated.
- Clean and dry the stone before testing.
- Keep the probe away from any surrounding metal.
- Verify the report details directly through IGI report lookup.
Independent lab certification is always the proper reference point. A tester reading can support a report, but it should never replace one. You can verify your report at IGI report lookup.
What to Do If You Still Cannot Find the Number
If you still cannot locate the inscription, the fastest route is to share the report number and your order details with us and we will help you verify everything step by step.
You can also review our main page on diamond certification for additional context on grading standards.
Quick Summary
- Verify the report number through IGI and match all key specs.
- The inscription is microscopic and can be difficult to view without correct tools.
- Budget handheld testers can give inaccurate readings.
- Certification remains the primary source of truth.
If you would like us to double-check your details with you, email us at hello@diamond-labs.co.uk.