Most laboratory-grown diamonds of half a carat and up come with a report from IGI (International Gemological Institute). Here's how to read one, line by line.
Header: report number and date
The report number is the key to everything. Enter it on IGI's website to see the digital record. The date shows when the stone was graded.
Description
It should state "Laboratory Grown Diamond". If it doesn't, stop and ask why.
Shape and cutting style
For example "Round Brilliant" or "Oval Modified Brilliant". This tells you the outline and the facet pattern.
Measurements
Length × width × depth in millimetres, for example 6.45 × 6.48 × 3.99 mm. Useful to compare apparent size and to confirm it's the same stone.
The 4Cs
- Carat weight: to two decimal places.
- Colour grade: D (colourless) to lower grades as tint increases.
- Clarity grade: from FL/IF down through VVS, VS, SI and I.
- Cut grade: for round brilliants, Ideal/Excellent down to Poor.
Our 4Cs guide explains what each grade means in practice.
Polish and symmetry
How smooth the facets are and how precisely they align. "Excellent" or "Very Good" is what you want.
Fluorescence
Whether the stone glows under UV light. "None" or "Faint" is typical for lab-grown stones.
Comments
This is where you'll find the growth method (CVD or HPHT) and any mention of post-growth treatment, for example "As Grown – No indication of post-growth treatment" or a note that the stone was treated. Always read this section.
Inscription
The report lists what is laser-inscribed on the girdle, typically the report number with a lab-grown identifier. Check it under a 10× loupe.
Proportions diagram
Shows table %, depth %, crown and pavilion angles, girdle thickness and culet. For rounds, these explain the cut grade.
The three things to always check
1. The report says laboratory-grown.
2. The number verifies online and matches the paper report.
3. The inscription on the stone matches the report.
Compare IGI and GIA in our certificate guide, or ask us for certified stones.
