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Standards of Diamond Appraisal

Jewelers around the world use the grading system developed by the Gemological Institute of America (GIA) that analyzes the carat weight, color, clarity, and cut of each gem. These are known as the 4Cs.

All center stone diamonds used in NIWAKA engagement rings are first graded by the GIA and then subjected to rigorous evaluation by in-house experts, ensuring that only diamonds of the highest quality are eventually selected.

In adherence with the Kimberley Process, all NIWAKA diamonds are certified as conflict-free.

Carat Weight

Carats are units of measurement for a diamond’s weight. Carats are abbreviated as “ct”, with 1 carat equaling 0.2 grams.


Diamonds are color graded on a 23-grade scale which uses letters from D to Z. While D color grade diamonds are considered colorless, Z color grade diamonds have a yellow hue.

NIWAKA engagement rings utilize only diamonds ranked as D, E, F, or G in color.


Clarity reflects the characteristics of a diamond’s transparency by examining the presence of inclusions or blemishes.

Evaluating a diamond’s clarity involves inspecting the stone’s surface and interior with a 10x magnification loupe. Clarity is assigned one of 11 grades, ranging from gems so perfect that even an experienced grader with a 10x loupe cannot find a flaw to those with inclusions visible to the naked eye.

NIWAKA engagement rings utilize only diamonds ranked between FL (Flawless) and SI1 (Slightly Included).

Has no Inclusions inside of the diamond or blemish on the outer surface of the diamond (visible by 10x magnification.)
Internal Flawless:
Has no internal inclusion (visible by 10x magnification) but may have minor blemishes on the outer surface of the diamond.
Very Very Slightly Included:
Has minute inclusions inside of the diamond.
Very Slightly Included:
Has very minor inclusions inside of the diamond.
Slightly Included:
Has minor inclusions inside of the diamond.
Has inclusions that are visible with the naked eye.


The appeal of a diamond is its brilliance. A stone that is well-cut will take in surrounding light and reflect it to emit a strong, clear glow.

The quality of a cut is evaluated through a comprehensive look at the diamond’s proportions, polish, and symmetry. This is the only one of the 4Cs that evaluates craftsmanship rather than a diamond’s natural features.

A diamond’s cut can be graded as Excellent, Very Good, Good, Fair, or Poor. NIWAKA utilizes only diamonds that have been judged to be Excellent.

The Cut of a Diamond

An evaluation of how well the shape of a diamond will reflect the maximum amount of light from the diamond.


The polish of the diamond's facets is evaluated on a five-point scale, from "poor" to "excellent".


The symmetry is evaluated on a five-point scale, from "poor" to "excellent".

Triple Excellent Diamonds

Diamonds called Triple Excellent are those that have received Excellent grades for their overall cut, polish, and symmetry. In other words, a Triple Excellent diamond is shining at its brightest.

For engagement ring center stones, NIWAKA utilizes only top-ranked diamonds considered to be Triple Excellent.

Diamond Grading Report

All NIWAKA engagement rings come with a grading report from the GIA, such as a GIA Diamond Grading Report or a GIA Diamond Dossier. This report includes an assessment of the diamond’s carat weight, color, clarity, and cut. The original developer of the 4Cs system, the Gemological Institute of America is a non-profit organization that provides grading services and trains gem appraisers.

Hard-copy reports will be provided to customers who placed their orders before February 1, 2023. Digital reports will be issued for orders placed on February 1, 2023 or later. You can access your digital diamond grading report from the About Your Diamonds page.

Diamond Experts

The 4Cs are an important indicator of a diamond’s worth, but NIWAKA has established even stricter selection guidelines, with in-house experts carefully choosing only diamonds of the highest quality. NIWAKA employs professionally trained gemologists, and all diamonds used in NIWAKA jewelry have been inspected one by one by these experienced specialists.

Gem inspection focuses primarily on clarity characteristics, proportions, polish, and symmetry of the diamond.

When evaluating clarity characteristics, appraisers use a microscope to identify whether the diamond has any internal features that obstruct the flow and reflection of light from the diamond.

They also appraise whether there are any surface irregularities that would interfere with the durability of the diamond.

Finally, the polish of the cut is checked to ensure that nothing affects the brilliance of the light coming from the stone or the sparkle of its surface.
By following these strict guidelines, NIWAKA’s diamond experts dedicate themselves to ensuring the beauty of NIWAKA jewelry.

Melee Diamonds

NIWAKA’s dedication to fine diamond quality doesn’t stop at the center stone. The melee diamonds are also inspected under the microscope by experienced appraisers in a rigorous selection process, allowing NIWAKA jewelry to shine brilliantly for many years.

The size and position of any inclusions are checked to make sure that they don’t affect the stone’s transparency or beauty, and the cut is carefully inspected for symmetry and balance.

Use of this uncompromising methodology allows for melee diamonds that will last a lifetime.