Diamonds · 5 min read · Published , updated
Diamond grading reports explained
A grading report is the independent record of a diamond’s characteristics. Here is what it contains and how to read one.
What a grading report is
A grading report is issued by an independent laboratory after gemmologists examine the diamond. It records the stone’s measurements, its 4Cs (carat, colour, clarity and, for round brilliants, cut) and further details such as polish, symmetry and fluorescence. It is not a valuation: it describes the diamond, it does not price it.
The grading laboratories
The Gemological Institute of America (GIA) is a non-profit institute founded in 1931. It developed the 4Cs and the international diamond grading system, and its reports are widely used as a reference. The International Gemological Institute (IGI), founded in Antwerp in 1975, is one of the largest grading laboratories in the world. Others include HRD Antwerp, the American Gem Society Laboratories (AGS) and GCAL. Each Lavandela diamond is graded by an independent laboratory, and the laboratory is named on its certificate and on the diamond’s page, with the report number.
How to read the key lines
- Carat weight: the diamond’s weight (one carat is 0.2 grams), not its size. Two stones of the same weight can face up differently depending on their proportions.
- Colour: graded from D (colourless) towards Z (light yellow or brown). D to F are colourless; G to J are near colourless.
- Clarity: from FL (flawless) through IF, VVS1–2, VS1–2 and SI1–2 to I1–3, describing the size, number and position of inclusions under 10× magnification.
- Cut: for round brilliants, an overall grade from Excellent to Poor describing how well the diamond returns light.
- Polish and symmetry: the finish of the facets and how precisely they align.
- Fluorescence: how the diamond glows under ultraviolet light. Most is invisible in daylight; strong blue fluorescence can occasionally make a stone look slightly hazy.
Checking a report
Many reports carry a number that is also laser-inscribed on the diamond’s girdle, and laboratories let you check a report number on their website. GIA offers this through its Report Check service. Your grading report is included with your order.
