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How to read a GIA Diamond Report

How to read a GIA Diamond Report

Posted in: Diamonds

GIA (Gemological Institute of America) is the creator of the 4’s and maintains best practices for evaluating diamond quality. The GIA diamond report represents an accurate, unbiased and scientific investigation of a diamond.

Each diamond comes with its own unique report number. You can use this number to look up your diamond online so you can always track down your diamond information. This webpage can be found here:

‘Grading Results’ accurately describes the carat, colour, clarity and cut grade of your diamond, otherwise commonly known as the ‘Four C’s’.

Carat weight is described to the nearest 100th of a carat. One carat is equal to 200 milligrams, or 0.2 grams and is written as ct.

Colour describes the diamonds lack of colour on a colour scale from D – Z (with D being colourless and Z being light yellow or brown).  Diamond is composed almost entirely of carbon but does contain traces of other elements. These elements cause diamonds to have body colours in shades of yellow, gray and brown.

Clarity refers to the number, position and size of inclusions and blemishes that occur naturally in diamonds (with Flawless being the least included to Included 3 being the most). Because diamonds form under tremendous heat and pressure, it’s extremely rare to find a diamond that lacks any internal or external characteristics.

On some GIA reports, clarity characteristics is described with a plotted diagram, with a key to symbols explanation.

For round brilliant diamonds, GIA has a cut grade scale that ranges from Excellent to Poor. Cut grade is used to describe the relative quality of the proportions and finish of a polished diamond taking into account seven characteristics:

  1. Polish
  2. Symmetry
  3. Weight ratio
  4. Durability
  5. Brightness
  6. Fire
  7. Scintillation

The diamond profile is shown to actual proportion and states the table percentage, crown angle, girdle thickness and depth percentage.

Fluorescence is stated on GIA diamond reports as another identifying factor on a scale ranging from None – Very Strong. Fluorescence is the visible light diamonds emit when they are exposed to invisible ultraviolet rays. On a GIA diamond report, fluorescence refers to the strength or intensity of the diamonds’ reaction to long-wave UV.   

GIA uses technology to ensure the diamond in question is natural and to identify any processes used to alter its colour or clarity.

A number of security features are present on a GIA report to authenticate the document.


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