How to Read an IGI Diamond Certificate

When you purchase a lab grown diamond, one of the most important documents you’ll receive is a diamond grading certificate—also called a diamond report. At Diamond Lab, we work with leading grading labs like IGI (International Gemological Institute) to ensure our stones meet international standards of quality and transparency.

But what do all those codes, numbers, and diagrams mean?

In this guide, we’ll break down how to read an IGI diamond certificate, what to look for, and how it can help you make an informed, confident jewellery purchase.

What Is the IGI and Why Does It Matter?

The International Gemological Institute (IGI) is one of the most recognised diamond grading authorities in the world. IGI is especially prominent in the lab grown diamond industry due to its early and consistent work with lab-created stones.

An IGI certificate provides an independent, objective assessment of your diamond’s characteristics. This document ensures:

• You’re getting what you paid for

• The diamond’s attributes (cut, colour, clarity, carat) are verified

• Transparency when comparing options

• Added value and trust in the stone

Key Sections of an IGI Diamond Certificate

Each IGI diamond report includes several technical sections, which together tell the full story of the stone’s quality and properties.

Let’s walk through each one.

🟠 1. Report Number and Shape

• Report Number: Unique identification number that is often laser-inscribed on the diamond’s girdle. This can be used to match your diamond to its certificate.

• Shape and Cutting Style: For example, Oval Brilliant, Radiant Cut, Pear Modified Brilliant, etc.

This section confirms you're reviewing the correct certificate for the correct stone.

🔵 2. Carat Weight

• Expressed to two decimal points (e.g., 1.02 ct)

• One carat = 0.20 grams

While often perceived as the most important factor, carat weight only tells you the size—not how sparkly or brilliant a diamond appears. Cut and proportions affect perceived size.

🟢 3. Colour Grade

• Graded from D (colourless) to Z (light yellow/brown)

• The closer to D, the more rare and valuable the diamond

IGI uses master stones and controlled lighting to assess the colour of each diamond. Most high-quality lab diamonds are in the D to F range.

🟣 4. Clarity Grade

• Based on internal (inclusions) and external (blemishes) characteristics

• Ranges from FL (Flawless) to I3 (Included)

• Common grades for high-quality lab diamonds include VVS1, VVS2, and VS1

Clarity affects both the appearance and light performance of the diamond. Inclusions may or may not be visible to the naked eye.

🟡 5. Cut Grade (For Round Diamonds Only)

• Ranges from Excellent, Very Good, Good, Fair, to Poor

• Cut grade reflects how well a diamond returns light—affecting sparkle and fire

Note: Fancy shapes like ovals or pears do not receive a formal cut grade, but symmetry and polish are still evaluated.

🔶 6. Polish and Symmetry

• Graded separately as Excellent, Very Good, etc.

• Polish refers to the surface smoothness

• Symmetry refers to how well the facets align

Both affect the diamond’s sparkle and are especially important in fancy shapes.

🔷 7. Fluorescence

• Describes how the diamond reacts to UV light

• Ranges from None to Strong

In most cases, fluorescence is not visible and doesn’t impact appearance, though strong fluorescence may affect transparency in some lighting.

🔳 8. Proportions Diagram

This visual section shows a technical drawing of the diamond’s shape, with:

• Table size (%)

• Depth (%)

• Crown and pavilion angles

• Girdle and culet descriptions

These values help assess how well the diamond is cut, especially for fancy shapes without a formal cut grade.

🔍 9. Clarity Characteristics Plot

A map of any inclusions or blemishes, shown from the top (crown view) and bottom (pavilion view). This helps identify your exact stone.

Symbols indicate:

• Crystals

• Clouds

• Needles

• Feathers

• Naturals

📌 10. Comments & Inscriptions

• Any treatments, enhancements, or growth processes (e.g. CVD, HPHT)

• Notes on features that may not be plotted

• Laser inscription details if applicable

💎 Want a piece with full certification? View the
👉 Luna Oval Solitaire Ring, available with IGI or GIA-certified lab grown diamonds.

How to Use Your Certificate When Buying

• Compare multiple stones side by side using identical grading reports

• Verify value before committing to price

• Request laser inscription to match diamond and certificate

• Ensure transparency from your jeweller

IGI vs GIA vs Other Labs: Is There a Difference?

IGI and GIA are both globally trusted labs. IGI is currently more dominant in the lab diamond sector, while GIA remains a leader in mined diamonds. The grading criteria are similar, though GIA certificates are sometimes more conservative.

At Diamond Lab, we only source stones certified by IGI or GIA, ensuring absolute credibility.

Final Thoughts: Why IGI Certificates Matter

When you're investing in a diamond, you're investing in more than just sparkle—you’re investing in trust, authenticity, and value. An IGI certificate ensures your lab grown diamond has been professionally evaluated for quality and ethical sourcing.

Understanding this document is key to making an informed choice—whether you’re selecting an engagement ring or designing a one-of-a-kind heirloom.

Still Have Questions? We’re Here to Help

Not sure how to compare reports or choose between two diamonds? We can guide you through every detail—cut quality, clarity visibility, table proportions, and more.

📍 Book a private consultation at our Perth showroom or online:
👉 Contact Diamond Lab