What Is an IGI Certificate? A Plain-English Guide
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When you buy a lab-grown diamond, you will often see the letters IGI. Here is what an IGI certificate is, what it tells you, and why it matters before you spend money on a diamond.
What is IGI?
IGI, the International Gemological Institute, is one of the world's largest independent gem-grading laboratories. It grades both natural and lab-grown diamonds and is the most widely used lab for lab-grown stones. Because IGI does not sell diamonds, its report is an independent, third-party description of the stone.
What does the certificate show?
- Origin: it states clearly that the diamond is laboratory-grown. Many reports also note the growth method (CVD or HPHT).
- Carat weight: the exact weight of the stone.
- Color grade: on the D-to-Z scale. D to F is colorless, G to J near-colorless.
- Clarity grade: from FL (flawless) through VVS and VS to SI and I. VS stones are eye-clean.
- Cut grade for round stones, plus polish and symmetry.
- Measurements in millimeters, and often a report number laser-inscribed on the stone's girdle.
Why it matters
Two diamonds that look similar online can differ a lot in quality and in value. A certificate means the grades come from an independent lab, not only from the seller. It also helps with insurance, resale and peace of mind.
Certificates and finished jewelry
For a single larger stone, such as a solitaire ring or a pair of studs, the report covers the main diamond. In pieces with many small stones, like tennis bracelets, the quality is described for the piece as a whole. At Diamond Leaders, lab-grown diamonds come with a free IGI certificate, and every lab-grown piece is clearly labeled lab-grown.
How to read the grades in plain English
Most of our lab-grown jewelry uses F color and VS clarity. In plain English, that means bright white and clean to the naked eye. Paying for D color or flawless clarity rarely makes a visible difference in finished jewelry, so it is usually better to put that money into a larger stone.
More on choosing quality in our Lab Diamond Guide and in lab-grown vs natural diamonds. Browse engagement rings, earrings and tennis bracelets.
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