Differences between IGI and GIA Diamond Certification Grading Standards

The Gemmological Institute of America (GIA), founded in 1931 as a non-profit research and education organization for diamonds, is the world’s foremost grading laboratory. They set the unified standard for diamond grading worldwide and remain today its most trusted name.

Diamond igi vs gia assessments evaluate a diamond’s 4 Cs (cut, colour, clarity and carat weight), proportions and inclusion plot. They also provide other information like fluorescence and symmetry.


IGI Vs GIA Diamonds is the world’s most esteemed diamond certification agency. They have been graders of diamonds for decades, building an unbeatable reputation that cannot be replaced.

They are renowned for their stringent grading standards and reliable reports; however, there are some drawbacks as well.

One of the primary concerns with GIA is their slow certification process, which can be frustrating for consumers. Furthermore, their grading standards may not be completely impartial when it comes to lab-grown diamonds.

GIA Extensive Report

When purchasing a diamond, an independent laboratory report should be considered. This can give you peace of mind and guarantee that the gemstone you purchase is genuine.

A GIA Extensive Report provides a comprehensive evaluation of a diamond. It includes plotted diagrams showing its proportions, polish and fluorescence.

The diamond’s grading report also includes a laser indentation of its unique report number on its girdle, making it easier to identify online. Security measures like GIA micro printing, watermarks, two-dimensional barcode and hologram are employed in order to maintain the report’s integrity.

GIA Colour Grades

GIA colour graders determine diamond colour by comparing them to a master set of gem quality stones under controlled lighting and precise viewing conditions. The GIA diamond colour scale ranges from D-Z, with each letter grade representing an identifiable range in hue appearance.

A completely colourless diamond is an uncommon occurrence, though many fall within a range from near-colourless to light yellow or brown. Some may undergo post-growth treatments such as High Pressure, High Temperature (HPHT) to alter their hue.

GIA diamond certification includes a report that details the grading process, including whether the diamond has undergone post-growth treatment. If this treatment is detected, the GIA diamond grading report will indicate it with an asterisk.

GIA Clarity Grades

When it comes to diamond clarity, both GIA and IGI assign grades from FL (Flawless) to I3. However, there are some key distinctions between their two grading standards.

The GIA’s clarity grading standards are more stringent than those of the IGI. It created the 4Cs (Cut, Colour, Clarity and Carat) system which is widely used around the globe today.

GIA Cut Grades

When purchasing diamonds, the cut grade is an important factor that will influence your satisfaction level. Not only does it shape the diamond’s appearance, but it also determines its fire, brilliance, symmetry and polish.

The GIA system assesses four aspects of cut, such as light performance (reflection and scattering), scintillation (amount of sparkle), pattern and contrast.

While it is beneficial to be familiar with the GIA cut grades, it’s essential to remember that even diamonds with excellent or ideal cuts may still appear poor if other factors aren’t taken into account. Stones with poor proportions, low weight ratio or unsteady craftsmanship often receive either an Ideal or Excellent grade from GIA.

GIA Polish Grades

The polish of a diamond is one of the most crucial factors in its light-handling ability. This allows the stone to achieve maximum brilliance, scintillation and dispersion.

Additionally, making sure the diamond is symmetrical can help ensure its value. Symmetry refers to the outline of the stone, facet arrangement and pointing, as well as table and culet cantering.


The GIA rates the presence of these features on a scale from Excellent to Poor, judging them independently from clarity characteristics (inclusions).

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